EPA/600/R-20/019 | January 2020
www.epa.gov/homeland-security-research
United States
Environmental Protection
Agency
&EPA
Portable Mercury Detector Testing
and Evaluation Report
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Disclaimer
The U.S. Environmental Protection Agency (EPA), through its Office of Research and
Development's Center for Environmental Solutions & Emergency Response (Homeland Security
& Materials Management Division), directed and managed this investigation through Contract
No. EP-C-15-008 with Jacobs Technology, Inc. (Jacobs). Jacobs' role did not include
establishing Agency policy. This report has been peer and administratively reviewed and
approved for publication as an EPA document. This report does not necessarily reflect the views
of the EPA. No official endorsement should be inferred. This report includes photographs of
commercially available products. The photographs are included for purposes of illustration only
and are not intended to imply that EPA approves or endorses the product or its manufacturer.
EPA does not endorse the purchase or sale of any commercial products or services.
Questions concerning this document, or its application should be addressed to the
following individual:
John Archer, MS, CIH
Homeland Security & Materials Management Division
Center for Environmental Solutions & Emergency Response
U.S. Environmental Protection Agency (MD-E343-06)
Office of Research and Development
109 T.W. Alexander Drive
Research Triangle Park, NC 27711
E-mail Address: Archer.John@epa.gov
Telephone No.: (919) 541-1151
Fax No.: (919) 541-0496
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Acknowledgments
The principal investigator from the U.S. Environmental Protection Agency (EPA),
through its Office of Research and Development's Center for Environmental Solutions &
Emergency Response (CESER), directed this effort with the support of a project team from
across EPA. The contributions of the individuals listed below have been a valued asset
throughout this effort.
EPA Principal Investigator
John Archer, CESER/ Homeland Security & Materials Management Division (HSMMD)
EPA Technical Reviewers
Timothy Boe, CESER/HSMMD
Peter Kariher, Center for Environmental Measurement & Modeling (CEMM)/Air
Methods Characterization Division (AMCD)
External Technical Reviewers
Richard Nickle, Centers for Disease Control and Prevention (CDC)/ATSDR Emergency
Response
Ron Howell, North Carolina State University, Environmental Health and Safety
EPA Quality Assurance Reviewer
Eletha Brady-Roberts, CESER
Jacobs Technology, Inc.
Abderrahmane Touati
Stella McDonald
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Executive Summary
The purpose of this project was to provide credible information on the selection and
implementation of technologies to protect human health and the environment during a response
and remediation effort following a spill or other release to the environment. This was achieved
by testing and evaluating multiple monitors capable of detecting mercury (Hg) in the ambient air.
Currently, these portable monitors are used by the EPA's emergency response on-scene
coordinators (OSC) to characterize Hg spills and provide air monitoring data when clearing
residential and commercial buildings after Hg cleanups. However, only one portable real-time
monitor has been used for clearance to date because evaluations indicated only that monitor was
able to provide equivalent results to the accepted integrated air sampling (sorbent tube) method.
Hence, the primary objective of this study was to determine if additional portable monitors
provided the sensitivity and accuracy to detect Hg concentrations in the air necessary for
building re-occupancy.
Five commercially available portable Hg detectors from two vendors (Ametek Arizona
Instrument LLC, Chandler, AZ, and Ohio Lumex, Solon, OH) were evaluated for their
performance outputs against a National Institute of Standards and Technology (NIST) traceable
saturated mercury vapor generated by a Tekran® Model 3310 Elemental Mercury Calibrator
(Tekran Instruments Corporation, Toronto, Canada). The five Hg instruments evaluated were
Ametek Arizona Instrument's Jerome® J405 and Jerome® J505 and Lumex's RA-915+, RA-
915M, and Light 915. Because of multiple malfunctions with the operation of the Lumex Light
915, testing was not completed with this instrument.
Each detector's performance under controlled laboratory conditions was evaluated
against EPA's Performance Specification (PS) 12A (US EPA. 2005). "Specifications and Test
Procedures for Total Vapor Phase Mercury Continuous Monitoring System in Stationary
Sources." PS 12A specifies that a mercury instrument is accurate if its measurements are within
20% relative accuracy (RA) of the standard method used. While this PS is not directly
applicable to portable Hg instruments, it does provide a metric for comparison that is appropriate
under the laboratory testing conditions. Each of the mercury detection instruments was evaluated
both with and without an interferent (ammonia, NH3) for accuracy, precision, and linearity. It
should be noted that integrated sorbent tube air samples actually collected in the field by EPA
OSCs during a mercury cleanup must adhere to the Superfund Contract Laboratory Program
(CLP) quality assurance/quality control requirements which may be less stringent than EPA PS
12 A.
The primary objective of the Hg detector testing was to determine if the instruments
could accurately detect Hg concentrations in the air below the Centers for Disease Control and
Prevention's Agency for Toxic Substances and Disease Registry (ATSDR) recommended action
level (clearance) of 1 |ig/m3 for normal residential occupancy (ATSDR. 2012). The performance
of each of these instruments is summarized below.
In summary, the Jerome® J505 and both the Lumex-RA 915 M and Lumex-RA 915+
instruments were found to be compliant with EPA PS 12Ai for Hg concentrations under 28.01
Hg/m3 and can be used to accurately characterize Hg contamination or provide clearance for an
indoor location. These instruments were observed to meet the detection and sensitivity
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requirements for assisting with a clearance determination based on the 1 |ig/m3 residential action
level (US EPA. 2019). However, the Jerome® J405 was less sensitive, with no detector responses
observed for target Hg concentrations below 1.10 |j,g/m3 and therefore was not in compliance
with EPA PS 12A. Additionally, the Lumex detectors had response times within a few seconds
(2 to 7 seconds), whereas the Jerome® J505 response times were measured in minutes (2 to 6
minutes), independent of the environmental conditions or the presence of NHa-interferent. These
response readiness times were based on both ambient and cold storage test conditions and
present an instrument-readiness caveat that users should be aware of. However, for Hg clearance
purposes, a response time in either seconds or minutes is likely not a concern.
Jerome® J405. For relatively low temperature and relative humidity (RH) conditions (10
°C, 19% RH, and 23 °C, 30% RH), no detector responses were observed for target Hg
concentrations below 1.10 |j,g/m3. Note that these concentrations were near the minimum of the
manufacturer's listed detection range of 0.5 to 999 |ig/m3 (ABLE Instruments & Controls, 2008).
Increases in temperature and RH (35 °C, 60% RH) resulted in a marked effect on the
sensitivity of the instrument, decreasing the level of the observed detection limit from 1.10
|ig/m3 to 0.25 |ig/m3, A significant increase in accuracy occurred as the challenge concentration
increased from 1.10 |ig/m3 {66.1% RA) to 17. 1 |ig/m3 (6.22% RA). The detector's response was
found to comply with EPA's PS 12A_for Hg concentrations ranging from 17.1 to 28.0 |ig/m3.
The linearity of this instrument was found to be acceptable (R2 >0.99) for concentrations greater
than 1.10 ng/m3, with a systematic bias of greater than 22%. The limit of detection (LOD) was
not calculated for this instrument since no response was detected for Hg concentrations lower
than 1.10 ng/m3, and no measurements were made between 1.10 and 5.00 |j,g/m3. The precision
of the Jerome J405 was observed to increase as the challenge concentration increased from 0.25
|ig/m3 (relative standard deviation [RSD] = 55%) to 28.0 |ig/m3 (RSD = 0.95%).
Jerome® J505. This detector outperformed the J405 in terms of sensitivity, with an
observed detector response at 0.25 |ig/m3 for all tested operating conditions. Moreover, the J505
was found to be compliant with EPA PS 12A and can be considered accurate for the Hg target
range between 0.0 to 28.0 |ig/m3. Although an increase in temperature (up to 35 °C) and RH
(60%>) reduced the accuracy of the instrument, it was still in compliance with the EPA's
performance specifications for accuracy. The response times of the Jerome® J505 were
measured in minutes and response time doubled following cold storage.
The Jerome J505 exhibited a slope near a value of 1 (> 0.97), with relatively good
linearity (R2 >0.99) for Hg concentrations between 0 and 28.0 |j,g/m3. The calculated LOD, based
on instrument response-residuals when no Hg was introduced, was equal to 0.07 |j,g/m3. The
precision was also increased from the lowest target Hg concentration (0.25 |ig/m3, RSD = 17%)
to the highest target concentration (28.0 |ig/m3, RSD = 0.45%).
Lumex-RA 915 M and Lumex-RA 915+. No significant differences were observed for
either accuracy or precision in a comparison of the Lumex-RA 915+ and the Lumex-RA 915M
for all target Hg concentrations tested. Both instruments were found to be compliant with EPA's
performance specifications for Hg continuous emission measurements for two of the tested
environmental conditions (10 °C, 19% RH, and 23 °C, 30% RH). Increasing the temperature and
RH (to 35 °C and 60% RH) affected the performance of the instrument, with an RA at or greater
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than 20%.
Both the 915M and 915+ Lumex detectors exhibited similar slopes (0.91- 0.93) that
tended to slightly underestimate the value of the Hg concentration of the Tekran calibrator. The
linearity of the two detectors (0.96 > R2 > 0.98) and their calculated LODs (< 0.002 |ag/m3) were
also similar. The similarity in the findings are not surprising since the RA-915M is an updated
version of the RA-915+, with a similar engineering design but including some additional features
such as a lightweight outer casing, a built-in backlit screen display, an automated calibration test
cell, and a USB cable connection.
The precision of both instruments was very good for the range of Hg concentrations
evaluated in this study, with a less than 1.7% RSD for an Hg challenge concentration greater
than 0.50 |ig/m3.
All of the detectors' response times were evaluated to determine the time required for
readiness, accuracy, and speed after the instrument is powered on after being stored in a cold
environment (~ 5 °C) and in a warmer environment (24 °C). Both the Jerome J405, which uses a
gold film sensor technology, and, to a lesser extent the Lumex RA-915M, which uses atomic
absorption spectrometry at 254 nm with Zeeman correction for background absorption for
interference-free measurement, produced rapid ready-time responses of 2 to 3 seconds and 5 to 7
seconds, respectively, independent of the environmental conditions. However, the J505, which
uses atomic fluorescence spectroscopy, produced measured ready-time responses in minutes (2.7
minutes) rather than seconds at 24 °C, and the time was more than doubled (6.2 min) when it
was used following overnight cold storage at ^5 °C to 4.6 °C. In addition, the Jerome units have
the option to save and transfer test data via a USB connection, and the Lumex-RA 915M has an
option to connect to a computer, whereas the Lumex RA-915+ does not have either of these
options.
To determine the interference of an NH3-containing gas stream with the instruments'
performance, a gas mixture containing NH3 (7.863 ppm sulfur hexafluoride, 514.9 ppm
ammonia, and balance nitrogen) was introduced downstream of the Tekran® and RH equipment.
The target environmental conditions for the interference evaluations were 23 °C and 30% RH.
Interference evaluations were performed for the J405, J505, RA-915M, and RA-915+ detectors.
The overall results indicate that none of the detectors' responses were affected by the presence of
the NH3 interferent at the target challenge concentrations (0.0 |ig/m3 and 4.70 |ig/m3).
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Contents
Disclaimer i
Acknowledgments ii
Executive Summary iii
Figures vii
Tables vii
Acronyms and Abbreviations viii
1. Project Description and Objectives 9
1.1 Purpose 9
1.2 Objective 9
1.3 Experimental Design 10
1.4 Test Matrix 13
2. Material and Methods 15
2.1 Bench-Scale Testing Setup 15
2.2 Hg Generation/Calibration System 17
2.3 Fourier Transform Infrared Spectroscopy (FTIR) 18
2.4 Portable Mercury Detectors 18
2.4.1 Lumex Hg Detectors 19
2.4.2 Jerome Hg Detectors 19
2.5 Measurement of Temperature and RH 20
3. Results 21
3.1 Environmental Test Conditions 21
3.2 Cold Start Evaluation 21
3.3 Detector Response Evaluation 23
3.3.1 Jerome 405 26
3.3.2 Jerome 505 26
3.3.3 Lumex-RA-915M 27
3.3.4 Lumex-RA-915+ 28
3.4 Detector Linearity 28
3.5 Interference Evaluation 32
3.6 Operational Observations 34
3.7 Summary of Detector Performance 34
References 37
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Figures
Figure 2-1: Bench-Scale Testing Setup 16
Figure 2-2. Tekran Model 3310 17
Figure 2-2. Lumex RA-915+, 915M, and Lumex Light-915 detector 19
Figure 2-3. Jerome J405 and J505 detectors 20
Figure 3-1. Jerome J405 Linear Regression Curve 29
Figure 3-2. Jerome J505 Linear Regression Curve 30
Figure 3-3. Lumex 915M Linear Regression Curve 31
Figure 3-4. Lumex 915M+ Linear Regression Curve 32
Tables
Table 1-1. List of the Performance Parameters 12
Table 1-2. Tested Environmental Conditions 13
Table 1-3. Test Target Hg Concentrations 13
Table 1-4. Interference Test Target Conditions 15
Table 2-1. Tekran Source Temperatures and Flow Rates for Hg Challenge Concentrations 18
Table 3-1. Average Environmental Conditions 21
Table 3-2. DQIs for Critical Measurements 21
Table 3-2. Measured Ready-Time Following Ambient and Cold Storage 22
Table 3-3. Average Detector Response and Accuracy per Environmental Conditions 24
Table 3-4. Average Environmental Conditions 33
Table 3-5. Average NH3 concentration (ppm ± SD) 33
Table 3-6. Average Detector Response and Accuracy per Environmental Conditions With and
Without NH3 Interferent 33
Table 3-7. Operational Considerations for use of the Hg Detectors 34
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Acronyms and Abbreviations
AT SDR
Agency for Toxic Substances and Disease Registry
°C
degrees Celsius
CESER
Center for Environmental Solutions & Emergency Response
DAS
data acquisition system
dscm
dry standard cubic meter
DQI
Data quality indicators
EPA
Environmental Protection Agency
FTIR
Fourier Transform Infrared Spectroscopy
ERTG
Emergency Response Technical Group
HSMMD
Homeland Security & Materials Management Division
HSRP
Homeland Security Research Program
L
Liter
LOD
Limit of detection
Hg
Mercury
|ig/m3
micrograms per cubic meter
MDL
method detection limit
m
Meter
min
Minutes
mL
Milliliter
ng/m3
nanograms per cubic meter
nh3
Ammonia
NIST
National Institute of Standards and Technology
OSC
On-Scene Coordinator
ppm
parts per million
QC
quality control
RA
relative accuracy
RH
relative humidity
RPD
Relative percent difference
RSD
relative standard deviation
T
temperature
SHEM
Safety, Health and Environmental Management
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1. Project Description and Objectives
The U.S. Environmental Protection Agency's (EPA's) Homeland Security Research
Program (HSRP) provides credible information that is used to protect human health and the
environment from adverse impacts arising from terrorist threats and other contamination
incidents. Within the HSRP, the Center for Environmental Solutions & Emergency Response
(CESER), Homeland Security & Materials Management Division (HSMMD) conducts research
to provide expertise and guidance on the selection and implementation of decontamination
methods that may lead to significant reductions in the time and cost of wide area remediation
efforts.
EPA's HSMMD research and technical expertise supports EPA's regional on-scene
coordinators (OSCs) and response teams, as well as state and local emergency response agencies.
As part of this support, HSMMD recently evaluated technologies to address indoor mercury (Hg)
measurement and monitoring needs. Reliable real-time portable Hg detectors are integral to the
OSCs and provide an agreed-upon alternative (ATSDR, 2012) to integrated area air sampling
using sorbent tubes (US EPA, 2012) to assess indoor Hg contamination as well as to permit re-
occupancy of a building following a Hg contamination incident. The current use of a real-time
portable monitor for clearance sampling was based on an extensive comparison of portable
monitor readings over 8 hours with NIOSH 6009 sorbent tube sampling results from samples
collected over the same 8-hour time period in the same location. The testing specified in this
document is part of HSMMD's efforts to identify and verify the performance of existing portable
chemical detectors to detect Hg in air.
1.1 Purpose
Responding to an accident, fire, or deliberate chemical release can potentially expose first
responders to harmful levels of toxic or corrosive chemicals. Additionally, following a
contaminant release indoors, it is essential to protect the public health and provide a clearance
determination following cleanup efforts. To minimize such exposures, first responders and
emergency management professionals need reliable, sensitive, and portable monitoring devices
that can rapidly indicate the presence of chemical hazards. The purpose of this work was to test
and evaluate multiple Hg detectors that can detect Hg in the ambient air. These portable monitors
are used by the EPA OSC community to obtain data for contamination screening and/or clearing
residential and commercial buildings after Hg cleanups, depending on the measurement range of
the instrument. All parties involved in a cleanup must agree to the use of portable monitors for
clearance sampling, for This project purpose was to determine which instruments meet the
detection and sensitivity requirements for assisting with a clearance determination using the
ATSDR recommended action level of 1 |ig/m3 (ATSDR. 2012).
1.2 Objective
This report summarizes a project that evaluated the performance and operational
characteristics of five portable Hg monitors. Specifically, the accuracy, precision, and
interference effects from ammonia (NH3) were evaluated for each Hg monitor. Additional
interferents such as VOCs were identified but were not able to be tested at this time due to
9
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project constraints.
The overall objective was to provide the Emergency Response Technical Group (ERTG)
with objective data on the performance of the portable Hg monitors that could be used for
clearance sampling following a mercury release to the environment (indoors or outdoors).
Previous comparisons were made between real-time portable instruments and the NIOSH 6009
sorbent tube method (Singhvi et al, 2001, 2003). Based on the results from these comparative
studies, EPA and ATSDR came to an agreement that EPA OSCs could use the Ohio Lumex
915+ instrument for clearance sampling if specified criteria were followed.
1.3 Experimental Design
Portable Hg detectors developed by Ohio Lumex (Cleveland, OH) and AMETEK
Arizona Instruments (Chandler, AZ) were evaluated for accuracy, precision, and linearity during
exposure to varying environmental conditions and interferences. Detector sensors were exposed
to a range of elemental Hg vapor concentrations at targeted relative humidity (RH) and
temperature (mercury vapor and external) conditions. All target Hg gases were produced by a Hg
generator (Tekran® Model 3310 Elemental Mercury Calibrator, Tekran Instrument Corporation,
Knoxville, TN) that generates concentrations of mercury by using NIST-traceable saturated
mercury vapor. The design was intended to evaluate the operation of the detectors in the variable
temperature and RH environments that would be encountered in the field in different parts of the
world throughout different seasons.
The following input/output characteristics were evaluated for each detector:
• Calibration
A seven-point calibration curve over the dynamic range was constructed by using varying
Hg vapor concentrations while the temperature and RH were held constant. The objective of
constructing the calibration range was to determine the lower and upper measurement limits for
each sensor using the signal output range. The lower limit was defined as the minimum input Hg
concentration that would cause a detector output that exceeded three times the signal-to-noise
ratio of the sensor when Hg was not present. The upper limit of the range was defined as the
maximum concentration at which the linearity of the calibration curve was not compromised. For
these tests, the lower limit of each instrument was of higher importance for clearing a building,
so the focus of the calibration curve was on the lower end of instrument sensitivity.
• Relative Accuracy (RA)
The RA (%) is defined by EPA Performance Specification 12A (US EPA. 2005) as the
absolute mean difference between the mean Hg concentrations determined by the Hg detectors
and the value determined by the reference method (RM) plus the 2.5% error confidence
coefficient of the detector measurement series divided by the mean of the RM reference method
tests. The calculation of RA (%) is described in the following equations:
(1)
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where \d\ is the absolute mean difference between the mean Hg detector responses
(|ig/m3) and the actual input concentration:
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generated by the Tekran® Model 3310 calibrator.
• Cold Start Evaluation
Response situations may not allow the time for instruments to warm up that would be
available if operated in a laboratory setting. Monitoring instruments may need to provide full
operational capabilities rapidly. Consequently, the portable Hg detectors were tested for the
delay in time between turning the instrument on and its readiness for hazard detection, and for
the accuracy and speed of response under such use. The speed for these capabilities was
determined under two separate startup conditions: (1) for an overnight startup from room
temperature and (2) after 24 hours in cold storage.
• Interference Effects
In emergency response situations, the local air may contain chemical compounds or
mixtures that, although relatively innocuous, may mask or alter the response of a portable Hg
detector. Examples of such potential interferences may be cleaning supplies, paint vapors, cat
urine, or vehicle exhaust. The effect of potential interferences was assessed because such
compounds can potentially produce two types of errors with the portable detectors: (1) erroneous
reporting of the presence of Hg when none is present (false positives, FP) or (2) reduction in
sensitivity or masking of response to Hg (false negatives, FN). The former error can waste time
and resources in responding to an emergency; the latter error can expose responding personnel
and the public to hazardous conditions.
Interference testing was performed by introducing a gas mixture containing ammonia
(NH3) (7.863 ppm sulfur hexafluoride, 514.9 ppm ammonia, and balance nitrogen) downstream
of the Hg vapor generator and RH equipment. The target NH3 concentration was the odor
threshold of 8 to 10 ppm. The performance parameters that were investigated during interference
testing are listed in Table 1-1.
Table 1-1. List of the Performance Parameters
Parameter
Objective
Basis of Comparison
Calibration
Determine usable range and linearity of
detector
Detector readings at various concentrations of
Hg challenge
Accuracy
Characterize agreement of detector readings
with reference results
Compare detector readings to known Hg
concentration or reference method results
Temperature and RH
Effects
Evaluate effect of temperature and RH on
detector performance
Target Hg challenges at different temperature
and RH conditions
Cold Start Behavior
Evaluate effect of storage temperature on
detector performance at startup
Compare response/recovery times,
repeatability, and accuracy, after startup from
cold storage
Interference
Effects
Evaluate effect of contaminants that may
interfere with detector performance
Sample interferents in clean air and along
with target Hg concentration
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1.4 Test Matrix
A series of tests were performed at increasing temperatures and RH parameters to
simulate a range of real-world operating environment conditions consisting of humid, dry, hot,
and cold conditions. The tested environmental conditions (Table 1-2) were 10 °C and 19% RH,
23 °C and 30% RH, and 35 °C and 60% RH. Some more extreme target conditions, such as 35
°C and 80% RH, were attempted, but could not be reached and maintained because of limited
resources in controlling the RH at such levels.
For each test, the room temperature (environmental chamber) was maintained at the same
temperature as the conditioned challenge gas.
Table 1-2. Tested Environmental Conditions
Environmental
Condition
Target Hg Vapor and Room
Temperatures (°C)
Target Hg Vapor RH
(%)
A
10
19
B
23
30
C
35
60
The portable detectors were exposed to seven Hg concentrations at each of the three
environmental conditions listed in Table 1-3, totaling 21 tests. Hg setpoints that were pre-
programmed in the Tekran calibrator and previously verified by an independent sampling
method were selected for evaluation. The Hg vapor concentrations in micrograms per cubic
meter (|ig/m3) are listed in Table 2-2. The primary goal of this testing was to evaluate detector
performance at low concentrations at or below the current EPA clearance level for residential
buildings of 1 |ig/m3 to determine whether detectors other than the Lumex 915+ could be used
for clearance sampling by EPA's OSCs.
Additionally, the effect of interferences that might mask or alter the response of a
portable Hg detector were evaluated. The test matrix originally included interference effects
from volatile organic compounds (VOCs) and ammonia; however, due to constraints of time and
gas availability, interference testing was limited to ammonia, as shown in Table 1-4. Ammonia
was deemed more likely to be found in indoor environments and as such, was prioritized first in
the interference tests.
Table 1-3. Test Target Hg Concentrations
Level
Generated Hg Vapor Concentration (jig/m3)
1
0.000
2
0.250
3
0.501
4
1.100
5
4.700
6
17.110
7
28.012
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Table 1-4. Interference Test Target Conditions
Test
Generated Hg Vapor Concentration (|jg/m3)
Presence of NH3 (8 ppm)
1
0.000
N
2
0.000
Y
3a
0.250
Y
4a
0.501
Y
5
1.100
Y
6b
4.700
N
7b
4.700
Y
a Test not performed with Lumex915 M, Lumex 915+, Jerome J405, or Jerome J505
b Test not performed with Lumex 915 Light
2. Material and Methods
This section describes the experimental testing and materials, including the portable Hg
detectors, Hg generator, and the Fourier Transform Infrared Spectroscopy (FTIR) equipment
used for interference measurements.
2.1 Bench-Scale Testing Setup
The bench scale testing setup is shown in Figure 2-1. It consisted of the Tekran Hg
calibration system, a control chamber that provided a temperature-controlled environment to
house the sample tubing and the sampling manifold, the portable Hg detectors, a humidification
system, and an interferent loop with a digital mass flow controller. The entire setup was housed
within a temperature-controlled environmental test chamber, which was maintained at the target
operating temperature.
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Figure 2-1: Bench-Scale Testing Setup
A slipstream of the dry Hg vapor generated by the Tekran calibrator was humidified to
the target RH using a heated, high-flow gas humidity bottle (Fuel Cell Technologies, Inc.,
Albuquerque, NM). For the interference tests using NH3, a second slipstream from the Hg
generator was used to introduce the gas interferent (NH3) to the bulk flow just after the split
streams were rejoined. A digital mass flow controller (Smart TraklOO, Sierra Instruments, Inc.,
Monterey, C A) was used to control the flow rate of the interferent gas to the bulk flow that was
introduced into the gas manifold inside the temperature-controlled chamber. Once inside the
chamber, the bulk flow traveled through a 10-foot length of sample tubing for additional mixing
and temperature adjustment before entering the sampling manifold.
The temperature within the sampling manifold was measured using a standard K-Type
thermocouple, and the RH was measured with a digital temperature/RH probe (HMP60. Vaisala,
Helsinki, Finland). The intake air hose for each of the Lumex detectors was passed through pre-
drilled openings located on the front side of the control chamber and connected to the sampling
manifold. Quarter-inch sample tubing was used to connect the Jerome detectors to the sampling
manifold. The entire length of each intake air hose and the quarter-inch sample tubing was
maintained inside the control chamber. Although the detectors were maintained outside the
control chamber, they were positioned against the outer walls in a manner that prevented
exposure of the intake hoses and quarter-inch sample lines.
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The control chamber provided a temperature-controlled environment to house the sample
tubing and the sampling manifold. The temperature-controlled chamber consisted of a modified
Rubbermaid 48-quart chest cooler (Newell Brands Inc., Atlanta, GA). Two 3/8" tubes (a supply
and return) were installed in the back of the chamber to circulate the temperature-controlled
water through a 240-mm water-regulated row heat exchanger with two computer fans, attached
to promote air circulation over the radiator coils. The temperature-controlled water that flowed
through the heat exchanger was conditioned and pumped by a refrigerating circulator (Isotemp
30165, Fisher Scientific, Waltham, MA, USA).
2.2 Hg Generation/Calibration System
All target Hg gases were generated by a Tekran® Model 3310 Elemental Mercury
Calibrator (Figure 2-2). The Hg calibrator allows high-level Hg monitoring systems to be
accurately calibrated using elemental Hg. The Model 3310 allows both multi-point calibrations
and standard additions to be automatically initiated. The unit generates known Hg concentrations
using a NIST-traceable temperature-controlled saturated Hg vapor source. According to the
manufacturer, the chamber of the instrument contains 1 ml. of mercury (13.5 g) immobilized on
a proprietary sorbent bed of high surface area. The equilibration chamber temperature is
controlled from 5 °C to 50 °C using an oven. The flow of nitrogen or dry air through the chamber
is controlled by a digital mass flow controller. The nitrogen or dry air exiting the chamber is
saturated with mercury vapor, and this stream is diluted with nitrogen or dry air into the
concentration range of interest. The output concentration is controlled by setting the flow rates.
The unit also generates a mercury-free zero flow so that blank measurements can be performed.
Figure 2-2. Tekran Model 3310
Hg concentrations of 0.00 jig/m3 (zero-air), 0.250 jig/m3, 0.501 jig/m3, 1.100 |ig/m3,
4.700 |ig/m3, 17.110 |ag/m3, and 28.012 |ig/m3 were tested. Because the Tekran calibrator was
designed to perform in lower ranges, the upper measurement ranges of the instruments could not
be evaluated. Table 2-1 shows the associated flow rates and source temperatures for each
challenge concentration.
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Table 2-1. Tekran Source Temperatures and Flow Rates for Hg Challenge Concentrations
Generated Hg Vapor
(Ug/m3)
Hg Source Temperature
Set Point (°C)
Source Flow
Rate (mL/min)
0.00
-
0
0.250
4.0
2.1
0.501
4.0
4.19
1.100
4.0
9.21
4.700
7.0
23.87
17.11
25.0
18.51
28.01
25.0
30.33
2.3 Fourier Transform Infrared Spectroscopy (FTIR)
FTIR was employed to make quantitative measurements of NH3 in the bulk flow. FTIR is
capable of measuring both inorganic and organic species in complex matrices due to the
specificity of the wavelength for the corresponding analyte. FTIR relies on the specific
vibrational energy (wavelength) transitions of IR light being absorbed by a molecule. Molecules
sensitive in the IR region generate a specific spectral plot, with sharp peaks in various regions of
the plot depending on the particular molecule or class of molecule. This molecular dependence
allows FTIR to measure multiple species of both organic and inorganic compounds
simultaneously.
Measurements for NH3, the interference gas, were made using an FTIR system (MultiGas
2030 CEM, MKS Instruments Inc., Andover, MA). This system has a 5.11-meter path length
cell, and the gas flow rate from the mercury generator and ammonia tank being analyzed was
approximately 4 liters per minute (LPM). The system is designed to operate at 191°C for
applications such as stack monitoring and combustion emissions monitoring. The high-
temperature cell allows the system to measure water vapor up to 40% by volume and minimize
acid gas condensation. The system's detector is liquid-nitrogen cooled and uses a helium neon
reference laser. The data acquisition system collects and averages 64 scans over a one-minute
period to generate an average NH3 concentration. The data collection software generated a text
spreadsheet file with the various component concentrations, operating data such as pressure and
temperature, and spectra residuals or detection limits.
2.4 Portable Mercury Detectors
Five commercially available portable Hg detectors were evaluated in this investigation:
the Lumex RA-915+, RA-915M, and Light 915 (Ohio Lumex, Cleveland, OH), and AMETEK's
Jerome® J505 and Jerome® J405 (AMETEK Arizona Instruments, Chandler, AZ). Due to
multiple malfunctions with the Lumex Light 915, testing was not able to be completed with this
second-generation instrument. Testing is anticipated for the next generation of the Lumex Light
(to be available in 2019to assess its capabilities for clearance sampling compared to the other
detectors.
Detector testing requires a basis for establishing the performance of the tested
18
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technologies. For this evaluation, the assessment of technology performance was based on the
delivery of known concentrations of Hg and interferents in controlled clean airstreams. NIST-
traceable saturated mercury vapor generated by a Tekran® Model 3310 Elemental Mercury
Calibrator was used to confirm the delivered concentrations and test conditions. It should be
noted that this laboratory comparison is under controlled conditions and is not intended to
simulate a mercury spill in a residential setting where additional interferences such as dust, dirt
and other factors such as a recirculating heat or air conditioning system may affect monitoring.
However, for an initial comparison to known concentrations of Hg vapor under specific test
conditions, this was a necessary first step in evaluating the portable instruments.
2.4.1 Lumex Hg Detectors
The Lumex RA-915+ has been discontinued and replaced by the RA-915M, but the 915+
is still being serviced. It has historically been used for clearance sampling by EPA. As an
updated version of the RA-915+, the RA-915M offers the same design and engineering as its
predecessor but includes features such as a new lightweight outer casing, built-in backlit screen
display, an automated calibration test cell, and a USB cable connection. All Lumex instruments
use atomic absorption technology for detection as well as Zeeman Background Correction to
eliminate interference. The detection range of the RA-915+ is 2.0 ng/m3 to 20,000 ng/m' and for
the RA-915M is 2.0 ng/m3 to 30,000 ng?im3 in ambient air. These instruments are typically used
for the clearance of Hg-contaminated areas, and the 915+ has been identified as an acceptable
alternative (ATSDR. 2012) to the modified N10SH 6009 method (US EPA, 2012). These
Lumex instruments are not necessarily appropriate for initial screening following a Hg spill
indoors since the upper limit of detection is similar to or less than time-weighted average
occupational exposure limits for Hg (25-50 |ig/m3). ATSDR considers readings from a properly
calibrated Lumex Mercury Vapor Analyzer, that are representative of 8 hours of exposure at the
point of sampling, as comparable to the NIOSH 6009 method in the range of 0.1-10 ug/m3
(Singhvi, 2003) and will accept these in lieu of laboratory analysis (ATSDR. 2012). The Lumex
Light-915 is a "scaled-down" version of the 915M and is appropriate for ambient air
measurement applications that do not require the lower detection li mits of the others. The
detection range of the Light-915 is reported to be 0.10 fig/m3 - 3,000 (jg/m3. Figure 2-2 shows
the Lumex Hg detectors.
Figure 2-2. Lumex RA-915+, 915M, and Lumex Light-915 detector
2.4.2 Jerome Hg Detectors
The Jerome® J405 (Figure 2-3) is a portable Hg air monitor that has been redesigned in
19
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recent years to increase its sensitivity. The J405 utilizes the industry-proven, inherently stable,
and reliable gold film sensor technology and simple, one-button operation. This sensor requires
periodic sensor regeneration. The monitor has an ergonomically designed handle, a more
lightweight exterior case, and significantly lower detection capabilities (0.5 jig/m3). The J405 has
a detection range of 0.5 ug/nr to 999 jig/nv5 with a resolution of 0.01 (ig/m3. It is equipped with
an internal pump that draws the sample at a flow rate of 750 ± 50 mL/min as well as an optional
internal data logging system.
The Jerome® J505 detector (Figure 2-3) is a portable fluorescence spectroscopy analyzer,
which allows the detection cell to be simpler, smaller, lighter weight, and more durable than
competing spectroscopy instruments. The highly efficient optical cell requires less flow to purge
the system than other detectors, allowing the J505 to run at a lower flow rate, minimizing sample
dilution. This feature eliminates nearly all interferences. The J505 has a detection range of 0.05
ug/nv' to 500 ug/nr' with a resolution of 0.01 ug/m3. It is equipped with an internal pump that
draws the sample at a flow rate of 1 L/min as well as an optional internal data logging system.
Figure 2-3. Jerome J405 and J505 detectors
2.5 Measurement of Temperature and RH
The RH and temperature in the chamber were measured with a Vaisala HMP110, A Re-
type thermocouple was used for the primary temperature measurement. Both of the instruments
were used to monitor the conditions in real time. The specifications for the Vaisala transmitter
and the K-type thermocouple are shown in Table 2-2.
Table 2-2. Relative Humidity and Temperature Measurement Specifications
Parameter
Vaisala HMP110
K-Type Thermocouple
RH range (%)
0-100
NA
RH accuracy: 0-90%
±1.5%
NA
RH accuracy: 90-100%
±2.5%
NA
RH resolution
0.001%
NA
Temperature range
-14 to 80 °C
-200 to 1200 °C
Temperature accuracy
±0.2 °C ®,20 °C
± 1.2 °C,@ 25 C
Temperature resolution
0.001 °c
0.01 °c
20
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3. Results
This section discusses the testing results for both the Lumex and AMETEK series of
detectors at the selected Hg concentrations and under different operating conditions. The Ohio
Lumex instruments (915+, 915M, and 915 Light) reported Hg concentrations in ng/m3. Results
from the other instruments reported in this section were converted to |ig/m3 for consistency.
Additionally, standard curves, best-fit equations, and R2 values are provided for the responses
over the entire challenge concentration range (0 to 28 |ig/m3) and up to 1.10 |ig/m3 Hg to assess
the linearity at the lower concentration range.
3.1 Environmental Test Conditions
The target environmental conditions for accuracy and precision tests (Table 3-1) were intended
to replicate real-word operating temperatures and RH conditions. Table 3-1 details the average
temperature (°C) and RH (%) of the bulk gas measured at the sampling manifold, and the room
temperature of the test facility at each environmental condition.
Table 3-1. Average Environmental Conditions
Environmental
Condition
Avg. Room Temperature
(± RSD)
Avg. Manifold Temperature
(± RSD)
Avg. Manifold RH
(± RSD)
A
10.02 ±0.078
9.9 ±0.020
19.5 ±0.26
B
23.8 ±0.017
23.5 ±0.0081
29.7 ±0.029
C
34.9 ±0.021
35.6 ±0.0049
59.6 ±0.037
RSD = Relative Standard Deviation
The results demonstrate that the environmental conditions were fully controlled and are within
the acceptance criteria set for the data quality indicators (DQIs) listed in Table 3-2 for this
project.
Table 3-2. DQIs for Critical Measurements
Measurement Parameter
Analysis Method
Accuracy Target
Real-time Hg concentration
Tekran Hg calibrator
±5%
RH (%)
Vaisala HMD53 (0-
100%)
± 3.5% full scale from
factory
Temperature (T)
K-type thermocouple
± 2 °C
Differential time
Computer clock
1% of reading
3.2 Cold Start Evaluation
The purpose of the rapid response tests was to determine the time required for readiness,
accuracy, and speed after powering on the instrument following storage in a temperature-
controlled environment ~5 °C and 24 °C for replicating cold and hot startup temperatures,
21
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respectively. For comparison, these characteristics were evaluated first the J405, J505, and 915M
instruments powered off and stored overnight at an ambient temperature and then when powered
off and stored overnight in a laboratory refrigerator. The cold start testing evaluation was
performed in a temperature-controlled laboratory environment.
The Lumex 915+ was not included in the rapid response/cold start testing due to an
unidentified malfunction. When attempting to take samples with the unit, the display screen read
"Low Rad" and the Hg concentration readings were very unstable. The Lumex 915+ was
operable during every other test. Similarly, the 915-Light was not available for this rapid
response/cold start evaluation at the time of testing due to an ongoing malfunction.
Prior to conducting the cold storage series of the rapid response tests, the detectors were
stored overnight in the refrigerator for approximately 23.4 hours at an average temperature of 4.6
°C (± 0.30 RSD) and an average RH of 68.4 % (± 0.086 RSD). Prior to the ambient storage
evaluations, the detectors were powered off and placed on a laboratory bench in the temperature-
controlled laboratory.
The challenge gas was generated and brought to stable temperature and RH conditions
prior to testing. Once the temperature and RH of the challenge gas were stable, a detector was
removed from the refrigerator (for cold storage tests) or the laboratory bench (for ambient
storage tests), then connected to the sampling manifold and immediately powered on. The time
required for the detectors to become ready for sampling once powered on, or the ready-time, was
recorded. Each detector was evaluated individually while the others remained powered off in the
storage location until testing.
Table 3-2 details the ready-time for the detectors both immediately following storage at
room temperature and after overnight cold storage.
Table 3-2. Measured Ready-Time Following Ambient and Cold Storage
Detectors Following Ambient Storage
Start-up Step
Time (hh:mm:ss)
Detectors
J405
J505
915M
Power On (time)
16:21:23
15:47:30
16:31:35
Ready to Sample (time)
16:21:25
15:50:12
16:31:42
Total Time (s)
2
162
7
Detectors Following Cold Storage
Detectors
J405
J505
915M
Power On (time)
15:48:05
15:59:34
16:17:25
Ready to Sample (time)
15:48:08
16:05:47
16:17:30
Total Time (s)
3
373
5
22
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The Jerome J405, which uses a gold film sensor technology, and to a lesser extent the
Lumex 915M, which uses cold vapor atomic absorption spectroscopy, produced measured ready-
time responses of 2 to 3 seconds and 5 to 7 seconds, respectively, independent of the temperature
of the sensors. The Jerome J505, which uses the atomic fluorescence spectroscopy technique,
produced measured ready-time responses on the order of minutes rather than the seconds
reported for the other two tested detectors. The Jerome J505 ready-response time doubled when
it was powered on following overnight cold storage at 4.6 °C compared to when it was stored in
ambient temperatures overnight. The relatively higher ready-time for the J-505 is due to a
prescribed warming and stabilizing sequence included in the control system of the instrument.
Sampling can be triggered only when a flashing "Warming Up" message displayed on its screen
disappears.
3.3 Detector Response Evaluation
Relative accuracy was the measure used for evaluating the acceptability of the tested
detectors by comparison against concurrent set outputs of the Tekran calibration system used as
the RM. At each environmental condition, the response of each detector was recorded
approximately every 2 minutes over a 20-minute test duration. Precision, as assessed by the
RSD, was represented by the reproducibility of the detector's response during the 20-minute
exposure.
According to EPA PS 12A, an instrument is accurate if its measurements are with 20%
RA relative to the standard method used. Alternatively, if the mean RM is less than 5.0 [j,g/dscm,
the results are acceptable if the absolute value of the difference between the mean RM and the
instrument values does not exceed 1.0 [j,g/dscm.
Table 3-3 lists the average response (|ig/m3 Hg), RPD (%), RA (%), and Precision (%)
for each detector and at each prescribed condition.
23
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Table 3-3. Average Detector Response and Accuracy per Environmental Conditions
Jerome Detectors
Challenge
Concentration
(jig/m3)
J405
J505
Environmental
Conditions
Avg. Hg
Response
(jig/m3)
RPD
(%)
Relative
Accuracy
(RA) [%]
Precision
(%)
Avg. Hg
Response
(jig/m3)
RPD
(%)
Relative
Accuracy
(RA) [%]
Precision
(%)
0
NR
NA
0.017
NA
NA
0.25
NR
NA
0.26
4.00
23.9
17.3
Condition A
(10 C, 19%
RH)
0.5
NR
NA
0.51
2.00
10.4
6.08
1.1
0.576
-47.6
52.2
7.05
1.14
3.64
7.36
2.97
4.7
5.09
8.30
10.2
1.34
4.93
4.89
6.12
0.99
17.1
21.05
23.1
25.5
1.59
17.63
3.10
3.76
0.51
28.01
35.49
26.7
28.2
0.93
28.44
1.54
2.10
0.45
0
NR
NA
0
NA
0.25
NR
NA
0.25
0.00
19.8
14.6
Condition B
(23 C, 30%
RH)
0.5
NR
NA
0.5
0.00
8.22
5.87
1.1
0.1
-90.9
117
230
1.09
-0.91
5.38
3.91
4.7
4.71
0.21
2.01
1.42
4.81
2.34
3.37
0.82
17.1
20.27
18.5
20.8
1.53
17.29
1.11
1.49
0.32
28.01
34.48
23.1
24.27
0.766
28.39
1.36
1.91
0.46
0
NR
NA
0.1986
NA
0.25
0.496
98.4
235
55.3
0.178
-28.8
47.5
8.20
Condition C
(35 C, 60%
RH)
0.5
0.804
60.8
144
41.7
0.429
-14.2
22.5
3.00
1.1
1.52
38.2
66.7
16.8
0.952
-13.5
16.7
1.203
4.7
5.17
10.0
22.8
9.45
4.229
-10.0
11.4
2.061
17.1
17.70
3.51
6.22
1.92
14.75
-13.7
16.0
0.694
28.01
31.80
13.5
14.8
0.952
24.77
-11.6
12.3
0.690
RA = within EPA acceptance criterion
NR = No response from detector; NA = Not applicable
24
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Lumex Detectors
Challenge
Concentration
(jig/m3)
Challenge
Concentration
(jig/m3)
915M
915+
Avg. Hg
Response
(jig/m3)
RPD
(%)
Relative
Accuracy
(RA) [%]
Precision
(%)
Avg. Hg
Response
(jig/m3)
RPD
(%)
Relative
Accuracy
(RA) [%]
Precision
(%)
Condition A
(10 C, 19%
RH)
0
0.0126
NA
NA
0.0054
NA
NA
0.25
0.225
-10.0
11.4
1.21
0.222
-11.2
12.0
0.653
0.5
0.496
-0.80
1.82
0.878
0.497
-0.60
1.11
0.395
1.1
1.125
2.27
2.45
0.135
1.158
5.27
5.46
0.122
4.7
4.818
2.51
2.60
0.062
4.729
0.62
0.91
0.236
17.1
17.64
3.16
3.62
0.370
17.93
4.85
5.54
0.526
28.01
28.39
1.36
1.47
0.100
30.63
9.35
9.35
0.000
Condition B
(23 C, 30%
RH)
0
0.0017
NA
NA
0.0031
NA
NA
0.25
0.208
-16.8
21.9
4.84
0.231
-7.60
42.9
30.80
0.5
0.449
-10.2
10.5
0.215
0.449
-10.20
10.7
0.408
1.1
1.016
-7.64
7.80
0.159
1.026
-6.73
7.12
0.321
4.7
4.353
-7.38
7.62
0.205
4.238
-9.83
10.1
0.199
17.1
15.91
-6.96
7.26
0.284
16.20
-5.26
5.26
0.000
28.01
25.71
-8.21
8.36
0.136
27.05
-3.43
5.34
1.579
Condition C
(35 C, 60%
RH)
0
0.0031
NA
NA
0.0059
NA
NA
0.25
0.178
-28.8
43.1
16.32
0.1202
-51.92
54.4
54.38
0.5
0.375
-25.0
25.4
0.49
0.3163
-36.74
37.5
0.95
1.1
0.851
-22.6
23.9
0.55
0.7275
-33.86
34.1
0.30
4.7
3.776
-19.7
19.9
0.25
3.342
-28.89
29.1
0.24
17.1
13.04
-23.7
26.7
3.11
12.44
-27.25
28.0
0.83
28.01
21.94
-21.7
22.1
0.46
19.97
-28.70
29.6
0.94
RA = within EPA acceptance criterion
NR = No response from detector; NA = Not applicable
The following section discusses the results listed in Table 3-3, summarizing the
performance of each detector at different environmental conditions and Hg concentration levels.
25
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3.3.1 Jerome 405
Condition A (10 °C. 19% RID
The J405 failed to detect Hg concentrations < 0.5 |ig/m3. The detector response rendered
the highest RA when exposed to 4.7 |ig/m3, in compliance with the EPA PS 12A for acceptable
performance. The RA significantly decreased when exposed to both lower and higher
concentrations but, more so at lower concentrations.
At 1.10 |ig/m3, the precision (RSD) for the average response was 7.1%. The precision of
the instrument improved and was relatively stable for target Hg measurements between 4.70
|ig/m3 and 28.01 |ig/m3, with an RSD between 0.93 and 1.6%.
Condition B (23 °C, 30% RH)
As with Condition A, no Hg measurements were observed at or below the challenge
concentration of 0.5 |ig/m3. At the challenge concentration of 1.10 |ig/m3 the average detector
response was 117% below the actual concentration. The RA improved significantly during the
4.7 |ig/m3 exposure, with an average response 2% above the actual concentration. A significant
decrease in RA occurred when the challenge concentration increased to 17.1 |ig/m3 (20.8% RA)
and then slightly decreased again at 28.01 |ig/m3 (24.3% RA). During the evaluation, the
detector demonstrated optimal accuracy at the challenge concentration of 4.7 |ig/m3.
The calculated precision at the 1.1 |ig/m3 challenge concentration was very poor, with an
RSD of 230%. The precision was found to increase as the challenge Hg concentrations were set
at or above 4.7 |ig/m3. Within this elevated concentration range, the detector operated with
optimal precision between 0.77 and 1.5% RSD.
Condition C (35 °C, 60% RH)
At this environmental condition, the level of accuracy of Hg detection was reduced from
1.1 |ig/m3 to 0.25 |ig/m3, A significant increase in accuracy occurred as the challenge
concentration increased from 1.10 |ig/m3 (66.7% RA) to 17. 1 |ig/m3 (6.22 RA%). The detector
response was found to be in compliance with EPA PS 12A for concentrations above 17.1 |ig/m3.
The precision of the instrument was found to increase as the challenge concentration
increased from 0.25 |ig/m3 (RSD = 55.3%) to 28.01 |ig/m3 (RSD = 0.95%).
3.3.2 Jerome 505
Condition A (10 °C, 19% RH)
The Jerome 505 detector was found to be more sensitive than the Jerome 405 and was
able to detect Hg concentrations at 0.25 |ig/m3. The accuracy of the instrument was increased
with increasing target Hg concentrations, with an RA of 23.9% at the 0.25 |ig/m3 to less than
10.4%) for subsequent concentrations.
26
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The precision was found also to increase from the lowest target Hg concentration (0.25
|ig/m3, RSD = 17.3%) to the highest target concentration (28.1 |ig/m3, RSD = 0.45%).
Condition B (23 °C, 30% RH)
There was no significant change in either the relative accuracy or in the precision of the
detector with an increase in temperature and RH under condition A (10 °C, 19% RH).
Condition C (35 °C, 60 %RH)
The relative accuracy appeared to be impacted by an elevated RH and temperature
conditions at the lower target Hg concentration of 0.25 |ig/m3 with an RA greater than 47%, and
to a lesser extent at higher concentrations.
The precision of the average responses for the Hg challenge concentrations was found to
be dependent on the target Hg concentration mimicking the results obtained with conditions A
and B. The precision was relatively stable at concentrations > 0.5 |ig/m3, which was ostensibly
less susceptible to fluctuations in the input challenge concentrations. At these elevated T and RH
conditions, the Jerome 505 tended to underestimate Hg concentrations, while at ambient and low
T and RH conditions, this was not the case.
3.3.3 Lumex-RA-915XI
Condition A (10 °C. 19% RH)
Overall, the RA of the Lumex-RA 915M was in compliance with EPA PS 12A (< 20%
RA) for Hg measurements at all concentration levels tested in this study. The RA of the
instrument increased with increased Hg concentrations from 11.4% RA at 0.25 |ig/m3 to less
than 1.5% RA at 28.01 |ig/m3.
The precision of the 915M was very high for the range of Hg concentrations evaluated in
this study, with less than 0.3 % RSD for Hg challenge concentrations greater than 0.5 |ig/m3.
Condition B (23 °C, 30% RH)
The RA of the instrument was found to decrease from 3.89 + 3.75 % to 10.6 + 5.67 %
when the environmental conditions shifted from Condition A to Condition B. However,
according to EPA PS 12A criteria, the instrument was accurate for target Hg concentrations
greater than 0.5 |ig/m3 (RA <10.5%), and a precision less than 0.3%.
Condition C (35 °C. 60% RH)
Increasing both the temperature and the RH had a significant effect on the accuracy of the
detector. Relatively few of the targeted Hg concentrations measured were within the acceptable
EPA PS 12A criteria for an accurate continuous emission Hg instrument. Since the tested
condition included both elevated temperature and RH, it could not be determined which variable
effected the detector measurements.
27
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3.3.4 Lumex-RA-915+
All Tested Conditions
No substantial differences in performance were observed for the Lumex-RA 915+
instrument when compared to the Lumex-RA 915M in terms of accuracy or precision, as shown
in Table 3-3 for all of the target Hg concentrations tested.
3.4 Detector Linearity
One of the parameters that is used to assess the performance of an instrument is the
linearity of its calibration curve. A calibration curve was determined for each detector to predict
the unknown Hg concentrations based on the response of the instrument to the known standards
(or set concentrations) of the Tekran calibrator using the least square method. Linearity of the
calibration curve is usually expressed through the coefficient of determination, r2. The slope of
the calibration curve was used to determine the variance between the NIST-traceable Hg
generator and the actual measured values of the detector.
The linear regression line for the Jerome J405 detector, for relatively low temperature and
RH environmental conditions (Conditions A and B), is shown in Figure 3-1. The Jerome J405
exhibited a slope of 1.22, tending to overestimate the Hg concentration. The linearity of this
instrument appears to be good (R2 >0.99) for concentrations greater than 1.1 |ag/m\ with a
systematic bias of greater than 22%. The LOD was not calculated for this instrument since no
response was detected for Hg concentrations lower than 1.1 ng/m3, and no measurements were
made between 5.0 and 1.1 ng/m3.
The Jerome J505, as shown in Figure 3-2), exhibited a slope near a value of 1 (>0.97)
with relatively a good linearity (R2 >0.99) for Hg concentrations between 0 and 28.01 |j,g/m3.
The average calculated LOD based on linear regression for this instrument was 0.07 |j,g/m3.
Both Lumex detectors (915M, and 915+), shown in Figures 3-3, and 3-4, exhibited
similar slopes (0.91 and 0.93), respectively. They tend to slightly underestimate the value of the
Hg concentration of the Tekran calibrator (Figures 3-3, and 3-4). The linearity of the two
detectors (R2 = 0.98 and 0.96, respectively), and the calculated LODs (<0.002 |ig/m3) were also
found to be similar and within an acceptable range.
28
-------
40
35
30
cJT 25
E
O)
3: 20
UO
o
315
10
5
0
0 5 10 15 20 25 30
Tekran(ng/m3)
Figure 3-1. Jerome J405 Linear Regression Curve
29
-------
40
35
30
co 25
E
O)
E 20
LO
o
LO
15
10
5
0
J505
Linear Fit
Equation
y=a + b*x
Plot
J505
Weight
No Weighting
Intercept
0.01411 ±0.06301
Slope
0.97294 ±0.00517
Residual Sum of Squares
152.60569
Pearson's r
0.99662
R-Square (COD)
0.99326
Adj. R-Square
0.99323
0 5 10 15 20 25 30
Tekran(|Lig/m3)
Figure 3-2. Jerome J505 Linear Regression Curve
30
-------
40
35-
30-
c^25-
E
O)
s3 20 -
LO
5 15-
10-
Equation
y=a + b*x
Plot
915M
Weight
No Weighting
Intercept
0.00429 ± 0.09866
Slope
0.9106 ±0.008
Residual Sum of Squares
351.48202
Pearson's r
0.99109
R-Square (COD)
0.98226
Adj. R-Square
0.98218
Tekran(|Lig/m3)
Figure 3-3. Lumex 915M Linear Regression Curve
31
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40
35
30
00 25
O)
=L
+
LO
Oi
20
15
10
<> 915 +
— Linear Fit
Equation
y = a + b*x
Plot
915M+
Weight
No Weighting
Intercept
-0.09778 ±0.15822
Slope
0.92769 ±0.01258
Residual Sum of Squares
801.84654
Pearson's r
0.98026
R-Square (COD)
0.96092
Adj. R-Square
0.96074
Tekran(ng/m3)
Figure 3-4. Lumex 915+ Linear Regression Curve
3.5 Interference Evaluation
Interference testing was performed by introducing a gas mixture containing NH3 (7.863
ppm sulfur hexafluoride, 514.9 ppm ammonia, and balance nitrogen) downstream of the Tekran
and RH equipment. The target NH3 concentration was the odor threshold of 8 to 10 ppm.
The interference evaluation was initially designed to include the J405, J505, RA-915M,
RA-915+, and the RA-915 Light detectors. Within 2 weeks prior to testing, the 915 Light
detector underwent calibration by the manufacturer. However, three days into the interference
evaluation, the detector experienced an undiagnosed malfunction despite being re-evaluated by
the manufacturer a second time. Due to the repeated malfunctions of this instrument, the
interference evaluation for this detector is not reported.
The target environmental conditions for interference evaluations were 23 °C and 30%
RH. Table 3-4 details the actual temperature and RH measurements for both of these tests.
32
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Table 3-4. Average Environmental Conditions
Environmental Conditions
Avg. Room Temperature (°C ± SD)
23.0 ± 0.11
Avg. Manifold Temperature (°C ± SD)
23.0 ±0.08
Avg. Manifold RH (% ± SD)
30.0 ±0.58
Baseline comparisons were performed at select concentrations to evaluate response with
the detector exposed to Hg gas both with and without NH3 interference at constant RH and
constant temperatures and a minimal time difference between the interferent levels (present and
not present).
To minimize the potential for changes in the system, comparisons for each Hg level were
performed in succession, first with the interferent gas and then without it. Hg measurements were
collected after a 20-minute transition from the shutoff or opening of the NH3 feed downstream of
the Tekran calibrator output feed to allow the detectors and the FTIR to stabilize. The selected
Hg challenge concentrations with and without NH3 were 0.0 |ig/m3 and 4.70 |ig/m3, respectively.
The actual average concentrations of NH3 and method detection limits (MDLs) are
presented in Table 3-5. The MDLs were generated by multiplying the value of the spectral
residuals generated by the software by three.
Table 3-5. Average NH3 concentration (ppm ± SD)
Hg Setpoint (jig/m3)
NH3 (ppm)
Average
MDL
0.0
7.79 ±0.08
0.07
4.70
8.13 ±0.29
0.081
The results of the interference testing (average response [|ig/m3 Hg]), precision [%], and
RA) for each detector, with and without the NH3 interferent, are presented in Table 3-6.
Table 3-6. Average Detector Response and Accuracy per Environmental Conditions With and
Without NH3 Interferent
Jerome Detectors
Challenge
Concentration
(jig/m3)
NHj
(Interferent)
J405
J505
Avg. Hg
Response
(Hg/m3)
Relative
Accuracy
(RA) r%i
Precision
(%)
Avg. Hg
Response
(Ug/m3)
Relative
Accuracy
(RA) r%i
Precision
(%)
0
No
NR
NA
0.042
NA
Yes
NR
0.036
4.7
No
5.09
18.2
7.43
4.81
3.37
0.82
Yes
5.34
29
10.8
4.9
5.71
1.09
33
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Lumex Detectors
Challenge
Concentration
(jig/m3)
NHj
(Interferent)
915M
915+
Avg. Hg
Response
0ig/m3)
Relative
Accuracy
(RA) [%]
Precision
(%)
Avg. Hg
Response
Gig/m3)
Relative
Accuracy
(RA) [%]
Precision
(%)
0
No
0.047
NA
0.025
NA
Yes
0.031
0.016
4.7
No
4.41
6.1
0.03
4.259
9.5
0.13
Yes
4.38
7.8
0.76
4.238
11.1
1.14
3.6 Operational Observations
Operational observations for each of the detectors are presented in Table 3-7.
Table 3-7. Operational Considerations for use of the Hg Detectors
Hg Detector
Operational Observations
Jerome J505/J405
Option to save and transfer test data to a USB. Additionally, the tests could be conducted by
manually starting the analysis (pushing the "Test" button) or the unit could be programmed to
test at specific time intervals. The latter option works well with the USB data retrieval.
Lumex RA 915M
The option to connect the unit to a computer with a data cord was available but not utilized.
Lumex RA 915+
There was not an option to save data for future retrieval or transport data to a portable storage
device. Data had to be recorded manually. The lamp could be lit manually if necessary. Specific
computer software was not required.
Lumex RA 915 Light
The free manufacturer-provided software allowed, with a computer and data cord connection,
remote observation of real-time test data. Additionally, system diagnostics and actions such as
turning the pump on and off and lighting the lamp can be performed with the software. There is
no option to relight the lamp manually.
3.7 Summary of Detector Performance
Five commercially available portable Hg detectors from two vendors (AMETEK Arizona
Instruments and Ohio Lumex) were evaluated for their performance against NIST-traceable
saturated mercury vapor generated by a Tekran® Model 3310 Elemental Mercury Calibrator.
The five Hg instruments evaluated were AMETEK's Jerome® J405, and Jerome® J505, and
Lumex's RA-915+, RA-915M, and Lumex Light 915.
The calibrated instruments were on loan by the manufacturers and used as received. The
setup and operation of all the tested detectors was relatively simple, with no further calibration or
on-site modification required. Due to multiple malfunctions with the Lumex Light 915, testing
was completed with this second-generation instrument. In terms of operability and data retrieval,
the Jerome units and the Lumex RA 915M all include a USB interface for saving and
transferring test data test data. The Lumex RA 915+ does not have an option to save data for
future retrieval or transport data to a portable storage device.
34
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The Jerome® J405 did not perform very well, with no detector responses for target Hg
concentrations below 1.10 |ig/m3, and tended to overestimate the Hg concentration, with a
systematic bias greater than 22%. The Jerome® J505, however, outperformed the Jerome J405
across the tested range of concentrations in terms of sensitivity, with an observed detector
response at 0.25 |ig/m3. Moreover, the J505 was found to be compliant with EPA PS 12A and
can be considered an accurate instrument for Hg target ranges between 0.25 to 28.0 |ig/m3,
whereas the Jerome ® J405 did not demonstrate this accuracy.
Both Lumex-RA 915 M and Lumex-RA 915+ detectors were found to comply with the
EPA PS 12A criteria for Hg measurements and rendered similar responses for the tested
environmental conditions (10 °C, 19% RH, and 23 °C, 30% RH). Increasing both the temperature
and the RH of the environmental conditions (35 °C, 60% RH) hindered the performance of both
instruments; therefore, they cannot be considered accurate and reliable for high temperature and
RH conditions according to the EPA's specifications.
The overall results indicate that none of the detectors' responses were affected by the
presence of the NH3 interferent at the target challenge concentrations (0.0 |ig/m3 and 4.70
|ig/m3). The accuracy and precision of the instruments were in general lower in the presence of
NH3, but not sufficiently significant to affect the performance of the instruments.
The setup and operation of all the tested detectors was relatively simple, with no
calibration of the instruments required prior to their evaluation. The instruments were loaners
from the manufacturers and used in the condition received. In terms of operability and data
retrieval, the Jerome units, and the Lumex RA 915M included a USB interface for saving and
transferring test data. The Lumex RA 915+ does not have an option to save data for future
retrieval or transport data to a portable storage device.
Despite the successful testing of multiple ambient Hg monitors under varied conditions,
there are still additional questions to be answered. Testing summarized in this report generally
met project objectives to determine which instruments meet detection and sensitivity
requirements, under controlled conditions, for assisting with a Hg clearance determination.
However, providing additional data to strengthen support for these conclusions is warranted,
including actual field test conditions. Further evaluation of these instruments could be performed
over a larger Hg concentration range and under separate environmental conditions in addition to
other improvements. Also, additional testing will include direct comparisons to the NIOSH
Method 6009 laboratory-based sampling and include specific criteria as outlined in the EPA
Emergency Response Team (ERT) SOP (US EPA/ERTC, 2004) for comparison in a
representative "field" environment. Future recommended tests include:
• Extending the sampling time to 8 hours with the Lumex/Jerome J505 detectors and
compare the results to the currently used modified NIOSH 6009 (sorbent tube).
• Extending the Hg concentration range to the upper capacities of the Jerome instruments
• Operating in separate high RH and high temperature environments to decouple their
respective effect
• Adding additional interferents (e.g., volatile organic carbons) to the gas-containing Hg
stream
35
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Testing of a third-generation Lumex Light against the Lumex 915M and other "good
performing" detectors
Testing multiple detectors (two or three) of the same type to investigate variation
between instruments.
36
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References
ABLE Instalments & Controls, 2008. Jerome J505 J405 J431 Comparison Flyer.
https://able.co.uk/media/2013/12/14c Jerome J505 J405 431 Comparison-Flyer.pelf, accessed
September 28, 2018.
ATSDR, 2012. Agency for Toxic Substances and Disease Registry. Chemical-Specific Health
Consultation for Joint EPA/ATSDR National Mercury Cleanup Policy Workgroup - Action
Levels for Elemental Mercury Spills.
https://www.atsdr.cdc.gov/emergency response/action levels for elemental mercury spills 20
12.pdf, accessed October 9, 2018
OSHA Method ID-140. 1987; Rev. June 1991. Mercury Vapor in Workplace Atmospheres.
Occupational Safety and Health Administrations Technical Center: (OSHA- Method No. ID-
140). Salt Lake City, UT. 1987.
https://www.osha.gov/dts/sltc/methods/inorganic/idl40/idl40.html, accessed September 6, 2018.
Singhvi R, Turpin R, Kalnicky DJ, Patel J. Comparison of Field and Laboratory Methods for
Monitoring Metallic Mercury Vapor in Indoor Air. May 2001. Journal of Hazardous Materials
83(1-2):1-10
Singhvi, R, Kalnicky, D, Patel, J, and Mehra, Y. Comparison of Real-time and Laboratory
Analysis of Mercury Vapor in Indoor Air: Statistical Analysis Results. Canada: 2003.
US EPA/ERTC, Standard Operating Procedure #1827, Operation of the Lumex RA-915+
Analyzer for Measuring Mercury Vapor Concentrations in Ambient Air, Rev. 0.0, January 2004.
US EPA/ERTC, Standard Operating Procedure #1729, Analysis of Mercury in Air with a
Modified NIOSH 6009 Method, Rev. 4.0, January 2012.
US EPA, 2005. PS12a, EPA Promulgated Performance Specification Specifications and Test
Procedures for Total Vapor Phase Mercury Continuous Emission Monitoring Systems in
Stationary Sources: Performance specification 12a: 40 CFR 60. Appendix B; Fed. Register.
2005, 70, 28674-28677, accessed September 6, 2018.
US EPA, 2019, National Elemental Mercury Response Guidebook.
https://response.epa.gov/ documents/MercuryResponseGuidebook/National Elemental Mercury
Response Guidebook 2019.pdf
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vvEPA
United States
Environmental Protection
Agency
PRESORTED STANDARD
POSTAGE & FEES PAID
EPA
PERMIT NO. G-35
Office of Research and Development (8101R)
Washington, DC 20460
Official Business
Penalty for Private Use
$300
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