March 2001

Environmental Technology
Verification Report

Spectrex Inc. SafEye 227
Infrared

Open-Path Monitor

Prepared by

Baiteiie

. . . Putting Technology To Work

Battel le

Under a cooperative agreement with

SEPA U.S. Environmental Protection Agency

ET^ET/ Eraf


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March 2001

Environmental Technology Verification

Report

ETV Advanced Monitoring Systems Center

Spectrex Inc. SafEye 227
Infrared
Open-Path Monitor

By

Jeffrey Myers
Thomas Kelly
Charles Lawrie
Karen Riggs

Battelle
Columbus, Ohio 43201


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Notice

The U.S. Environmental Protection Agency (EPA), through its Office of Research and
Development, has financially supported and collaborated in the extramural program described
here. This document has been peer reviewed by the Agency and recommended for public release.
Mention of trade names or commercial products does not constitute endorsement or
recommendation by the EPA for use.

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Foreword

The U.S. EPA is charged by Congress with protecting the nation's air, water, and land resources.
Under a mandate of national environmental laws, the Agency strives to formulate and implement
actions leading to a compatible balance between human activities and the ability of natural
systems to support and nurture life. To meet this mandate, the EPA's Office of Research and
Development provides data and science support that can be used to solve environmental
problems and to build the scientific knowledge base needed to manage our ecological resources
wisely, to understand how pollutants affect our health, and to prevent or reduce environmental
risks.

The Environmental Technology Verification (ETV) Program has been established by the EPA to
verify the performance characteristics of innovative environmental technology across all media
and to report this objective information to permitters, buyers, and users of the technology, thus
substantially accelerating the entrance of new environmental technologies into the marketplace.
Verification organizations oversee and report verification activities based on testing and quality
assurance protocols developed with input from major stakeholders and customer groups asso-
ciated with the technology area. At present, six environmental technology areas are covered by
ETV. Information about each of the environmental technology areas covered by ETV can be
found on the Internet at http://www.epa.gov/etv.htm.

Effective verifications of monitoring technologies are needed to assess environmental quality and
to supply cost and performance data to select the most appropriate technology for that assess-
ment. In 1997, through a competitive cooperative agreement, Battelle was awarded EPA funding
and support to plan, coordinate, and conduct such verification tests for "Advanced Monitoring
Systems for Air, Water, and Soil" and report the results to the community at large. Information
concerning this specific environmental technology area can be found on the Internet at
http://www.epa.gov/etv/07/07_main.htm.

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Acknowledgments

The authors wish to acknowledge the support of all those who helped plan and conduct the
verification test, analyze the data, and prepare this report. In particular we would like to thank
Paul Webb and Andy Montgomery of Battelle. We also acknowledge the participation of
Jay Cooley and Eric Zinn of Spectrex Inc. in this verification test.

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Contents

Notice	 ii

Foreword 	iii

Acknowledgments	 iv

List of Abbreviations	ix

1.	Background	1

2.	Technology Description 	2

3.	Test Design and Procedures 	4

3.1	Introduction	4

3.2	Test Design 	6

3.3	Experimental Apparatus and Materials	8

3.3.1	Standard Gases 	8

3.3.2	Dilution Gas 	8

3.3.3	Gas Dilution System	8

3.3.4	Gas Cell	8

3.3.5	Temperature Sensor 	8

3.3.6	Relative Humidity (RH) Sensor	8

3.3.7	Carbon Dioxide Monitor	8

3.3.8	Target Gas Measurement 	9

3.4	Test Parameters	9

3.4.1	Minimum Detection Limit 	9

3.4.2	Linearity 	10

3.4.3	Accuracy	10

3.4.4	Precision	10

3.4.5	Interferences 	11

4.	Quality Assurance/Quality Control	12

4.1	Data Review and Validation	12

4.2	Changes from the Test/QA Plan	12

4.3	Calibration	14

4.3.1	Gas Dilution System	14

4.3.2	Temperature Sensor 	14

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4.3.3	RH Sensor	14

4.3.4	Carbon Dioxide Monitor	14

4.3.5	Target Gas Measurement 	14

4.4	Data Collection 	14

4.5	Audits 	15

4.5.1	Technical Systems Audit 	15

4.5.2	Performance Evaluation Audit	16

4.5.3	Data Quality Audit 	17

5.	Statistical Methods	18

5.1	Minimum Detection Limit	18

5.2	Linearity	18

5.3	Accuracy	18

5.4	Precision 	19

5.5	Interferences 	19

6.	Test Results	20

6.1	Minimum Detection Limit	20

6.2	Linearity	20

6.2.1	Source Strength Linearity	20

6.2.2	Concentration Linearity 	23

6.3	Accuracy	25

6.4	Precision 	26

6.5	Interferences 	28

6.6	Other Factors	29

6.6.1	Costs	29

6.6.2	Data Completeness	29

7.	Performance Summary	30

8.	References	31

Appendix A: Data Recording Sheet	 A-l

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Figures

Figure 2-1.	Spectrex SafEye 227 IR Open-Path Monitor	2

Figure 3-1.	Test Site at West Jefferson Facility	6

Figure 3-2.	Optical Open-Path Monitor Setup	7

Figure 6-1.	Source Strength Linearity Plot of the SafEye 227 	 23

Figure 6-2.	Concentration Linearity Plot of the SafEye 227 Challenged with Methane	24

Figure 6-3. Concentration Linearity Plot of the SafEye 227 Challenged with

Propane 	 24

Figure 6-4. Concentration Linearity Plot of the SafEye 227 Challenged with

Mixture 	25

Tables

Table 3-1. Target Gases and Concentrations for Testing the SafEye 227 	4

Table 3-2. Optical Open-Path Monitor Verification: Measurement

Order for Each Target Gas 	5

Table 4-1. Summary of Data Recording Process for the SafEye 227

Verification Test	15

Table 4-2.	Summary of Performance Evaluation Audit Procedures 	17

Table 6-1.	Minimum Detection Limits Data for the SafEye 227 	 21

Table 6-2.	Minimum Detection Limits of the SafEye 227 	 22

Table 6-3.	Source Strength Linearity of the SafEye 227 	 22

Table 6-4.	Concentration Linearity Data for the SafEye 227 	 23

Table 6-5.	Results of Accuracy Tests for the SafEye 227 	 26

Table 6-6.	Data from Precision Tests on the SafEye 227 	 27

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Table 6-7. Results of Precision Tests on the SafEye 227 	 27

Table 6-8. Concentration Data from Interference Tests on

the SafEye 227 	 28

Table 6-9. MDL Data from Interference Tests on the

SafEye 227 	 29

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List of Abbreviations

AMS	Advanced Monitoring Systems

CEM	continuous emission monitor

C02	carbon dioxide

EPA	U.S. Environmental Protection Agency

ETV	Environmental Technology Verification

GC	gas chromatograph

GC/FID	gas chromatography/flame ionization detection/mass spectrometry

Hg	mercury

H20	water

IR	infrared

LEL*m	lower explosive limit meters

MDL	minimum detection limit

ND	neutral density

NIST	National Institute of Standards and Technology

N2	nitrogen

ppmC	parts per million of carbon

QA/QC	quality assurance/quality control

QMP	Quality Management Plan

RH	relative humidity

RSD	relative standard deviation

TSA	technical systems audit

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Chapter 1
Background

The U.S. Environmental Protection Agency (EPA) has created the Environmental Technology
Verification (ETV) Program to facilitate the deployment of innovative environmental tech-
nologies through performance verification and dissemination of information. The goal of the
ETV Program is to further environmental protection by substantially accelerating the acceptance
and use of improved and cost-effective technologies. ETV seeks to achieve this goal by provid-
ing high quality, peer-reviewed data on technology performance to those involved in the design,
distribution, permitting, purchase, and use of environmental technologies.

ETV works in partnership with recognized standards and testing organizations; with stakeholder
groups that consist of regulators, vendor organizations, and permitters; and with the full
participation of individual technology developers. The program evaluates the performance of
innovative technologies by developing test plans that are responsive to the needs of stakeholders,
conducting field or laboratory tests (as appropriate), collecting and analyzing data, and preparing
peer-reviewed reports. All evaluations are conducted in accordance with rigorous quality
assurance protocols to ensure that data of known and adequate quality are generated and that the
results are defensible.

The EPA's National Exposure Research Laboratory and its verification organization partner,
Battelle, operate the Advanced Monitoring Systems (AMS) Center under ETV. The AMS Center
recently evaluated the performance of optical open-path monitors for use in ambient air or fence
line measurements. This verification report presents the procedures and results of the verification
test for the Spectrex Inc. SafEye 227 infrared (IR) open-path monitor.

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Chapter 2
Technology Description

The objective of the ETV AMS Center is to verify the performance characteristics of environ-
mental monitoring technologies for air, water, and soil. This verification report provides results
for the verification testing of the SafEye 227. The following description of the SafEye 227 is
based on information provided by the vendor.

The SafEye 227 is an alarm system that detects hydrocarbons with a high-frequency IR flash
source and two absorbed band sensors centered at the 3.4-ja wavelength. This design also
employs a dual-band reference that minimizes environmental factors such as moisture and other
background gases to maintain a high signal-to-noise ratio. Other performance features include
three levels of logic, four levels of automatic gain control, four built-in calibrations, two span
settings, and four flash rates. Operational integrity can be maintained with up to three degrees of
misalignment or up to 90% signal obscuration.

The SafEye 227 is made up of two components: a flash source and a detector. These components
can be separated to measure ambient gas concentrations over a path length from 1 to 140 meters.
The flash source projects a wavelength (specific for the type of gas to be measured) to the
detector over an unobstructed line of sight. The beam is attenuated when a hazardous gas
traverses it at any point along its path. The detector measures the amount of attenuation by means

of two narrow-band sensors and
compares this information to a third
reference sensor input that is not
affected by the subject gas or
environmental factors.

The detector's microprocessor
software interprets the data and
provides output signals in terms of
lower explosive limit *meters
(LEL*m). The detector transmits the
data via a 4 to 20 mA signal or an
RS485 port or, if a pre-set gas
concentration is exceeded, closes
one of three contacts.

Flash Source

SafEye

Detector

Figure 2-1. Spectrex SafEye 227 IR Open-Path
Monitor

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All the SafEye models (ultraviolet and infrared) are approved for industrial applications by
international standards: CENELEC explosion-proof enclosures (per EN 50014, 50018, and
50019), Underwriter's Laboratory, and Factory Method (Class I Division 1, Groups B, C, and D
and Class II Division 1, Groups E, F, and G).

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Chapter 3
Test Design and Procedures

3.1 Introduction

This verification test was conducted according to procedures specified in the Test/QA Plan for
Verification of Optical Open-Path Monitors 1(1) The test was designed to challenge the SafEye 227
in a manner simulating field operations and was modeled after Compendium Method TO-16.(2)
The monitor was challenged in a controlled and uniform manner, using an optically transparent
gas cell filled with known concentrations of a target gas. The gas cell was inserted into the
optical path of the monitor during operation under field conditions, simulating the presence of
the target gas in the ambient air.

The monitor was challenged with the three target gases commonly measured by this monitor at
known concentrations, and the measurement results were compared to the known concentration
of the target gas. The gases and concentrations used for testing the SafEye 227 are shown in
Table 3-1. The verification was conducted by measuring the three gases in a fixed sequence over
three days. The one-day sequence of activities for testing the monitor for a single gas is shown in
Table 3-2.

Table 3-1. Target Gases and Concentrations for Testing the SafEye 227



Concentration

Target Gas Concentration

Equivalent Gas Cell

Gas

Level

(LEL*m)a

Concentrationb



cl

1.0

33.3%

Methane

c2

2.0

66.6%



c3

3.0

100.0%



cl

1.0

14.8%

Propane

c2

2.5

35.0%



c3

5.0

70.0%



cl

0.96

30.7% methane

Mixture0





0.56% propane
80.0 ppm ethane



c2

1.9

61.3% methane
1.12% propane
160 ppm ethane



c3

2.9

92.0% methane
1.70% propane
240 nnm ethane

aLEL*m=lower explosive limit meters.
bLength of gas cell = 15.0 cm.
cBalance of gas mixtures was N2.

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Table 3-2. Optical Open-Path Monitor Verification: Measurement Order for Each Target Gas

Meas.
#

Gas Cell
Cone.

Activity

#of
Spectra

Times (min)
Integrate Equilibrate

Path Length

(m)

Verification Parameter
Calculated



n2

Change gas & stabilize



10

40



1

n2

Collect spectra

25

1

40

Accuracy, Concentration linearity, MDL



cla

Change gas & stabilize



10

40



2

cl

Collect spectra

5

1

40

Accuracy, Concentration linearity

3

cl

Collect spectra - ND lb

5

1

40

Source strength linearity

4

cl

Collect spectra - ND 2b

5

1

40

Source strength linearity

5

cl

Collect spectra - ND 3b

5

1

40

Source strength linearity



n2

Change gas & stabilize



10

40



6

n2

Collect spectra

5

1

40

Accuracy, Concentration linearity



c2

Change gas & stabilize



10

40



7

c2

Collect spectra

5

1

40

Accuracy, Concentration linearity, Interference Effect (Int.)



N2

Change gas & stabilize



10

40



8

n2

Collect spectra

5

1

40

Accuracy, Concentration linearity



c3

Change gas & stabilize



10

40



9

c3

Collect spectra

25

1

40

Accuracy, Concentration linearity, precision

10

c3

Collect spectra - ND lb

5

1

40

Source strength linearity

11

c3

Collect spectra - ND 2b

5

1

40

Source strength linearity

12

c3

Collect spectra - ND 3b

5

1

40

Source strength linearity

15

n2

Collect spectra

25

5

40

Concentration linearity, MDL





Change to Path length 2



20

130



16

n2

Collect spectra

5

5

130

Int.



c2

Change gas & stabilize



10

130



17

c2

Collect spectra

5

5

130

Int., Accuracy, Concentration linearity



n2

Change gas & stabilize



10

130



18

n2

Collect spectra

5

5

130

Int., Accuracy, Concentration linearity





Change to Path length 3



20

65



19

n2

Collect spectra

5

1

65

Int., Accuracy, Concentration linearity



c2

Change gas & stabilize



10

65



20

c2

Collect spectra

5

1

65

Int., Accuracy, Concentration linearity



n2

Change gas & stabilize



10

65



21

N,

Collect spectra

25

1

65

Int., MDL

aSee Table 3-1 for values of cl-c3 for three target gases.
bActivities completed for methane only.


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The target gas concentrations are presented in LEL*m. This refers to the lower llammability
limit of each target gas in air. The LELs for methane, propane, and ethane are 5.0%, 2.1%, and
3.0% by volume, respectively.^

3.2 Test Design

The verification test was performed near West Jefferson, Ohio, at an outdoor testing area
belonging to Battelle, between October 23 and October 27, 2000. Testing began between 7 and
8 a.m. and ended between 5 and 7 p.m. during these five days. During each of the test days,
there was consistently heavy fog (visibility was less than 100 m) and precipitation ranging from
a light drizzle to a moderate rain. This location provided sufficient length and a direct line of
sight for each of the path lengths used during the test, and provided an area that was away from
any chemical sources that might affect the testing. The same sampling location was used during
a previous period of testing of open-path optical monitors in April and May 2000. The open
space in the foreground of Figure 3-1 shows the test site at Battelle's West Jefferson facility.

Figure 3-1. Test Site at West Jefferson Facility

The SafEye 227 was challenged with the target gases at the concentrations shown in Table 3-1,
and the SafEye 227 measurement of light absorption by the monitor was compared to the known
concentration of the target gas. For each target gas, the monitor was set up as if it were operating
in the field, except that an optically transparent gas cell was placed in the light beam's path (see
Figure 3-2). National Institute of Standards and Technology (NIST)-traceable or commercially

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DETECTOR

GAS CELL

OPTICAL
PATH

GAS
DILUTION
SYSTEM

TO VENT

LIGHT
SOURCE

1

O

TARGET GAS
OR GASES

O

DILUTION GAS

Figure 3-2. Optical Open-Path Monitor Setup

certified standard gases, a calibrated gas diluter, and a supply of certified high-purity dilution
gas were used to supply the target gases to the gas cell.

Target gases were measured at different path lengths, integration times, source intensities, and
numbers of replicate measurements to assess

¦	Minimum detection limit (MDL)

¦	Source strength linearity

¦	Concentration linearity

¦	Accuracy

¦	Precision

¦	Sensitivity to atmospheric interferences.

The test procedures shown in Table 3-2 were nested, in that each measurement was used to
evaluate more than one of the above parameters. In Table 3-2, N2 in the gas cell concentration
column denotes a period of cell flushing with high-purity nitrogen. The denotations cl, c2, and
c3 refer to the concentrations shown in Table 3-1. The last column shows the parameters to be
calculated with the data from that measurement.

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3.3 Experimental Apparatus and Materials

3.3.1	Standard Gases

The standard gases used to produce target gas levels for the verification test were NIST-traceable
gases provided by Matheson Tri-Gas Inc. Gravimetrically blended cylinders of methane; pro-
pane; and a mixture of methane, propane, and ethane were used and specified to have an
accuracy of 2%.

3.3.2	Dilution Gas

The dilution gas was acid rain continuous emission monitor (CEM) zero grade nitrogen from
Scott Specialty Gas.

3.3.3	Gas Dilution System

The dilution system used to generate known concentrations of the target gases was an Environics
2020 (Serial No. 2428). This system had mass flow capabilities with an accuracy of approx-
imately ±1%. The dilution system accepted a flow of compressed gas standard for dilution with
high-purity nitrogen. It was capable of performing dilution ratios from 1:1 to at least 100:1.

3.3.4	Gas Cell

A vendor-provided gas cell 15 centimeters in length was integrated into the end of the detector.
This cell had two 1/4-inch tube fittings that allowed the target gas to flow through.

3.3.5	Temperature Sensor

An Omega CT485B temperature monitor (Serial No. 704012206W1) with a thermocouple and
a digital temperature readout was used to monitor ambient air and gas cell temperatures. This
sensor was operated in accordance with the manufacturer's instructions.

3.3.6	Relative Humidity (RH) Sensor

The RH sensor used to determine the ambient air humidity was an Omega CT485B RH monitor
(Serial No. 704012206W1) that used the chilled mirror principle. This sensor was operated in
accordance with the manufacturer's instructions. The manufacturer's accuracy specification of
this monitor was ±3% RH.

3.3.7	Carbon Dioxide Monitor

An electrochemical monitor (TSI Model 8551 carbon dioxide monitor, Serial No. 30357) was
used to monitor the level of carbon dioxide in ambient air during interference measurements.
This monitor was operated in accordance with the manufacturer's instructions.

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3.3.8 Target Gas Measurement

The concentrations of the target gases provided to the gas cell were determined by collecting a
sample at the exit of the gas cell using a pre-cleaned Summa® stainless steel air sampling
canister. The collected sample was then analyzed using gas chromatography with flame
ionization (GC/FID) or thermal conductivity detection.

A Varian 3700 gas chromatograph was used to analyze for methane at the percent concentration
levels. A thermal conductivity detector was used to measure the signal response. The compounds
were resolved using a 3-foot by 1/4-inch outside diameter molecular sieve 5A column and a
5-foot by 1/4-inch outside diameter Porapak Q column connected in series. The columns were
operated isothermally at 100°C. Argon was the carrier gas (40 cc/minute). A 1-cc sample loop
and six-port valve were used to manually inject samples and gas standard mixtures. Data
acquisition and peak integration were accomplished with a PC equipped with Chrom Perfect
software.

A Varian 3700 gas chromatograph was used to analyze for propane at the percent concentration
levels. A thermal conductivity detector was used to measure the signal response. The compounds
were resolved using an Altech CTR-I column. A 6-foot by 1/8-inch outside diameter inner
column was used for methane and was composed of a propriety porous polymer mixture. The
column was operated isothermally at 180°C. Helium was the carrier gas (25 cc/minute). A 1-cc
sample loop and six-port valve were used to manually inject samples and gas standard mixtures.
Data acquisition and peak integration were accomplished with a PC equipped with Chrom
Perfect software.

A Varian 3600 gas chromatograph was used to analyze for ethane at the ppm level and propane at
the low percent concentration level. An FID was used to measure the signal response. The
compounds were resolved using a stainless steel 15-foot by 1/8-inch outside diameter column
with phenyl isocyanate/Porasil C packing. The column was operated isothermally at 40 °C.
Helium was the carrier gas (25 cc/minute). A 1-cc sample loop and six-port valve were used to
manually inject samples and gas standard mixtures. Data acquisition and peak integration were
accomplished with a PC equipped with Chrom Perfect software.

3.4 Test Parameters

3.4.1 Minimum Detection Limit

The MDL was calculated for each target gas by supplying pure nitrogen to the gas cell in the
optical path of the monitor and taking a series of 25 single-beam spectra using integration times
of 1 and 5 minutes. The single-beam spectra were then used to create absorption spectra, using
each single-beam spectrum as the background for the next spectrum. The absorption spectra were
created by using the first and second single-beam spectra, the second and third, the third and
fourth, etc. The resulting 25 absorption spectra were then analyzed for the target gas. This
sequence of measurements was conducted at both integration times; twice at a 40-meter path

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length and once at a 65-meter path length. The MDL was defined as two times the standard
deviation of the calculated concentrations from the 25 absorption spectra.

3.4.2	Linearity

Two types of linearity were investigated during this verification: source strength and concentra-
tion. Source strength linearity was investigated by measuring the effects on the monitor's per-
formance by changing the source intensity. In the field, light signal levels can be attenuated by
mist, rain, snow, or dirty optical components. As a constant concentration of target gas was intro-
duced into the gas cell, the light intensity of the source was reduced by placing a series of
aluminum wire mesh screens in the path of the light to determine how the monitor's measure-
ments were affected by an attenuated light source. Three aluminum wire screens of various
meshes were placed in the beam path. These screens were approximately 1 foot square and had a
mesh spacing of approximately lA, 'A and 1 inch. At each of these attenuation levels, a
measurement was made and the monitor analyzed for the target gas.

Concentration linearity was investigated by challenging the SafEye 227 with each target gas at
the concentrations shown in Table 3-1, while the path length and integration time were kept
constant. At each concentration, the monitor response was recorded and its linearity evaluated by
comparing the recorded response with the input target gas concentration.

3.4.3	Accuracy

Accuracy of the monitor relative to the gas standards was verified by introducing known
concentrations of the target gas into the cell. The gas cell was first flushed with at least five cell
volumes of nitrogen, and a single-beam spectrum was recorded. The target gas was then intro-
duced into the cell and, after flushing with at least five cell volumes, a second single-beam
spectrum of the target gas was obtained. The cell was again flushed with at least five cell
volumes of nitrogen, and a third spectrum was recorded. The three spectra were analyzed for the
target gas, using the background selected by the vendor. The concentration of the target gas was
the result of analyzing the second spectrum minus the average of the first and third (flushed cell)
spectra.

The accuracy was evaluated at concentrations denoted as cl through c3, using an integration time
of 1 minute. The accuracy was then evaluated at concentration c2 using a 5-minute integration
time, and then again at concentration c2 using a 1-minute integration time during the interference
measurements (Table 3-2). The percent relative accuracy for an experimental condition is the
absolute value of the difference between the average monitor response and the reference monitor
response, divided by the reference monitor response, times 100 (see Section 5.3).

3.4.4	Precision

The procedure for determining precision was very similar to the procedure for determining
accuracy. The gas cell was flushed with at least five cell volumes of nitrogen. The target gas was
then introduced into the cell and, after flushing with at least five cell volumes, 25 absorption
spectra of the target gas were obtained. These spectra were analyzed for the target gas. The

10


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relative standard deviation (RSD) of this set of measurements was the precision at the target gas
concentration. Precision was evaluated by this procedure at one concentration of each of the
target gases (see Table 3-2).

3.4.5 Interferences

The effects of interfering gases were established by supplying the gas cell with a target gas and
varying the distance (i.e., the path length) between the source and detector of the monitor. The
purpose of the interference measurements was to determine the effects of the ambient atmo-
spheric gases on accuracy and MDL of the SafEye 227. Using two different integration times,
these tests were conducted to determine the effect of integration time on the monitor's ability to
perform measurements with interfering gases in the light path.

To determine the effect of the interferences, the path length was first set to 40 meters. The gas
cell was supplied with nitrogen; and, after flushing with at least five cell volumes, five single-
beam spectra were recorded. Next, the target gas was introduced into the cell and, after similarly
flushing the cell, five single-beam spectra were recorded. Finally, nitrogen was again introduced
into the cell, and five spectra were recorded.

The path length was then set to 130 and to 65 meters, and the entire measurement procedure was
repeated. Atmospheric concentrations of water and carbon dioxide were recorded at the begin-
ning and end of these measurements. The extent of interference was assessed in terms of the
monitor's sensitivity to these interferant gases in the optical path.

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Chapter 4
Quality Assurance/Quality Control

Quality assurance/quality control (QA/QC) procedures were performed in accordance with the
quality management plan (QMP) for the AMS Center(4) and the test/QA plan(1) for this
verification test.

4.1 Data Review and Validation

Test data were reviewed and approved by the Verification Testing Coordinator and disclosed to
the Verification Testing Leader. The Verification Testing Coordinator reviewed the raw data and
the data sheets that were generated each day. Laboratory record notebook entries also were
signed and dated.

4.2 Changes from the Test/QA Plan

Two types of changes from the test/QA plan could occur: planned changes to improve the test
procedures for a specific vendor (amendments) and changes that occurred unexpectedly
(deviations).

Before the verification test began, several planned amendments were made to the original
test/QA plan to improve the quality or efficiency of the test. These procedural changes were
implemented and, in each case, either increased the quality of the collected data set or removed
inefficiencies in the test, ultimately resulting in a reduced test duration. A brief summary of these
amendments is provided below:

¦	MDL was determined using twice the standard deviation, as described in Section 3.4.1 of the
test/QA plan. The test/QA plan inadvertently called for the MDL to be determined by two
different methods. The correct method was chosen and used during the verification test.

¦	The Summa® canister analysis procedure was changed from that specified in the test/QA
plan. The test/QA plan specified using Method 18 to determine the hydrocarbon emissions
from combustion or other source facilities. This method broadly describes an analysis
procedure, but does not specify how the analysis is to be done, and calls for the use of
Tedlar® bags rather than Summa® canisters. Instead of as described in the test/QA plan, the
analysis was done according to Battelle's GC/FID analysis procedure for canister samples.

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¦	The order of testing in the test/QA plan was changed. The test order was originally
developed to maximize the efficiency of the test procedure. Several improvements were
made to the test matrix to further improve its efficiency. For example, instead of conducting
all of the measurements for one gas and then changing to the next gas, all of the short path
measurements were conducted before moving to the long path. This was done because
changing the path length was more time consuming than changing the target gas.

¦	The test/QA plan specified that source strength linearity would be tested for each of the
gases. The original intent was to conduct this test for one gas only. The source strength
linearity test was, therefore, conducted only for a single gas.

¦	Although monitoring ambient carbon monoxide was part of the test/QA plan, it was decided
that carbon monoxide measurements would not add any useful information to the
verification. Therefore, no carbon monoxide monitoring was performed.

¦	The short and long path lengths in the test/QA plan, which were specified as 100 and

400 meters, were changed to meet the specific technology requirements of the SafEye 227.
In this verification test, path lengths of 40, 65, and 130 meters were used. The test/QA plan
did not specify gases for this IR technology.

¦	Gases were selected based upon the monitor's capability. In addition, the operating range
only permitted using three concentrations. Because of this change in the specific concentra-
tion, measurement #9 rather than measurement #14 was used to calculate precision.

Amendments required the approval of Battelle's Verification Testing Leader and Center

Manager. An amendment form was used for documentation and approval of all amendments.

Deviations from the test/QA plan were as follows:

¦	No independent performance evaluation was conducted for temperature during the
verification test.

¦	The independent performance evaluation conducted for relative humidity on September 23,
2000, gave results outside the acceptance criterion for this measurement set forth in the
test/QA plan.

¦	Measurement #15 was performed for a 1-minute integration time instead of a 5-minute
integration time.

Deviation reports have been filed for each deviation.

Neither the amendments nor the deviations had a significant impact on the test results used to

verify the performance of the SafEye 227.

13


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4.3 Calibration

4.3.1	Gas Dilution System

Mass flow controllers in the Environics 2020 gas dilution system were calibrated by the
manufacturer prior to the start of the verification test by means of a soap bubble flow meter.
Corrections were applied to the bubble meter data for pressure, temperature, and water content.

4.3.2	Temperature Sensor

The thermocouple was calibrated by Battelle's instrument calibration facility on September 21,
2000. This instrument has a one-year calibration period, and so was still within its calibration
interval.

4.3.3	RH Sensor

The RH sensor was calibrated by Battelle's instrument calibration facility on September 21,

2000.

4.3.4	Carbon Dioxide Monitor

The carbon dioxide monitor was calibrated by the supplier before testing using a commercially
prepared, certified standard of carbon dioxide in air. That standard was a certified gas of 0.20%
carbon dioxide in N2, NIST-traceable, with ± 2% analytical accuracy (Cylinder No. 55924, Air
Liquide America).

4.3.5	Target Gas Measurement

The GC instrumentation was calibrated for the target gases using certified standards for each gas,
with a multipoint calibration. A Scott II methane standard of 40% methane (Project #9286
Lot #92681C7) from Scott Specialty Gas was used to calibrate the Varian 3700 GC for methane.
A cylinder of propane (Matheson Instrument Purity -99.5%) was used to calibrate the Varian
3700 gas chromatograph (GC) for the measurements conducted at percent levels. Finally, a Scott
Specialty Gas calibration cylinder of 1020 ppmC propane (Scott cylinder # ALM025084) was
used to calibrate the Varian 3600 for measurements of propane and ethane conducted at low
percent levels.

4.4 Data Collection

Data acquisition was performed by both Battelle and the vendor during the test. Table 4-1
summarizes the type of data recorded (see also the example data recording form in Appendix A);
where, how often, and by whom the recording was made; and the disposition or subsequent
processing of the data. Data recorded by the vendor were turned over to Battelle staff imme-
diately upon completion of the test procedure. Test records were then converted to Excel
spreadsheet files.

14


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Table 4-1. Summary of Data Recording Process for the SafEye 227 Verification Test

Data Recorded

Recorded
By

Where
Recorded

When Recorded

Disposition of Data

Dates, Times, Test
Events

Battelle

Data Sheet

Start of each test,
whenever testing
conditions changed

Used to compile results,
manually entered into
spreadsheet as necessary

Test Parameters (temp.,
RH, etc.)

Battelle

Data Sheet

Every hour during
testing

Transferred to spreadsheet

Interference Gas
Concentrations

Battelle

Data Sheet

Before and after
each measurement
of target gas

Transferred to spreadsheet

Target Gas
Concentrations

Battelle

Data Sheet

At specified time
during each test

Transferred to spreadsheet

GC Concentrations

Battelle

PC Stored
Chromatograms

After GC analysis

Stored on PC and on
printouts

Optical Open-Path
Monitor Readings

Vendor

Vendor Printout

At specified time
during each test

Transferred to spreadsheet

4.5 Audits

4.5.1 Technical Systems Audit

No technical systems audit (TSA) was performed during this verification test. A technical
systems audit was performed on another open-path verification test during the initial testing of
this type of technology. The TSA of the test procedures was conducted on April 13 and 14,
during the period of verification testing in early 2000. The TSA was performed by Battelle's
Quality Manager as specified in the AMS Center QMP. The TSA ensures that the verification
test is conducted according to the test/QA plan and that all activities associated with the test are
in compliance with the AMS Center QMP. Specifically, the calibration sources and methods
used were reviewed and compared with test procedures specified in the test/QA plan. Equipment
calibration records and gas certificates of analysis were reviewed. The conduct of the testing was
observed, and the results were assessed.

All findings noted during the TSA on the above dates were documented and submitted to the
Verification Testing Coordinator for correction. The corrections were documented by the
Verification Testing Coordinator and reviewed by Battelle's Quality Manager, Verification
Testing Leader, and Center Manager. None of the findings adversely affected the quality or
outcome of this verification test, and all were resolved to the satisfaction of the Battelle Quality
Manager. The records concerning the TSA are permanently stored with the Battelle Quality
Manager.

15


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In addition to the internal TSA performed by Battelle's Quality Manager, an external TSA was
conducted by EPA on April 14, 2000, during a previous set of open-path monitor verifications.
The TSA conducted by EPA included all the components listed in the first paragraph of this
section. A single finding was noted in that external TSA, which was documented in a report to
the Battelle Center Manager for review. A response and corrective action were prepared and
returned to EPA. The finding did not adversely affect the quality or outcome of this verification
test. The results of both the Battelle and EPA TSAs were accounted for in preparing for testing
the SafEye 227.

4.5.2 Performance Evaluation Audit

A performance evaluation audit was conducted during the testing period to assess the quality of
the measurements made in the verification test. This audit addressed only those measurements
made by Battelle in conducting the verification test. The performance audit procedures
(Table 4-2) were performed by Battelle technical staff responsible for the measurements.
Battelle's Quality Manager assessed the results. The performance evaluation audit was conducted
by comparing test measurements to independent measurements or standards.

Each of the required procedures for the performance evaluation audit was conducted during the
testing period in accordance with the direction specified in the test/QA plan, except for the
deviations concerning the temperature and RH performance evaluations listed in Section 4.2 of
this report. The results from the performance evaluations are shown in Table 4-2. The tempera-
ture measurement agreed to within -0.4°C. The relative humidity agreed to only within 16% (i.e.,
within 8% RH at 50% RH).

The data quality of the study was not seriously impacted by the large percent difference between
the expected and actual readings of the RH monitor. The RH measurement is used to calculate
the absolute concentration of water vapor in the atmosphere in a test of the relative impact that
changes in atmospheric water concentration have on the open-path monitor's ability to correctly
measure the target gas of interest. That test is done by changing the optical path length by a large
amount, in a short period of time. Thus, the absolute accuracy of the RH measurement is not of
critical importance because the change in path length achieves the desired difference in water in
the path. When the carbon dioxide gas standard was compared, the monitor reading agreed to
within 1.4% of the expected value.

The target gas concentrations were audited by independent analysis of the test gas mixture
supplied to the gas cell during verification testing. This procedure involved collecting a sample
of the test gas mixture exiting the cell using a pre-cleaned and evacuated Summa®-polished
sampling canister. This gas sample was analyzed for methane, propane, and the gas mixture
described in Table 3-1. Calibration of the GC was based on the standards cited in Section 4.3.5.
The results of the performance audit for the target gas concentrations were mostly within 10% of
the expected concentrations, which met the test/QA plan criterion. Three of the four propane
measurements had 14%, 14%, and 11% differences, which were outside the criterion. The
mixture gas of methane, ethane, and propane was analyzed for methane and resulted in
differences of -6.7%, -2.1%, and -2.5%, which met the test/QA plan criterion.

16


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Table 4-2. Summary of Performance Evaluation Audit Procedures

Measurement
Audited

Audit Procedure

Reference
Reading

Monitor
Reading

Difference

Acceptance
Criteria

Temperature

Compare to independent

19°C

18.6°C

-0.4°C

< 3°C



temperature measurement











(Hg thermometer)









RH

Compare to independent

42% RH

50% RH

8% RH

± 5% RH



RH measurement (wet/dry











bulb device)









Carbon dioxide

Compare measurement

800 ppm

811 ppm

1.4%

± 10%

concentration

using another CO2











standard from the same











supplier









Methane

Compare to results of GC

100%

100.1%

0.1%

< 10%

Methane

analysis of canister

66%

62.2%

-5.8%

< 10%

Methane

sample

33%

32.3%

-2.1%

< 10%

Propane



14%

15.9%

14%

< 10%

Propane



35%

39.8%

14%

< 10%

Propane



70%

77.6%

11%

< 10%

Propane



0.56%

0.55%

-1.5%

< 10%

Mixture 1 -



31%

28.9%

-6.7%

< 10%

31% Methane











Mixture 2 -



61%

59.7%

-2.1%

< 10%

61% Methane











Mixture 3 -



92%

89.7%

-2.5%

< 10%

92% Methane











Field blank and background samples were also taken with Summa® canisters, with resulting
analyses showing non-detects for the target gas concentrations.

4.5.3 Data Quality Audit

Battelle's Quality Manager audited at least 10% of the verification data acquired in the verifica-
tion test. The Quality Manager traced the data from initial acquisition, through reduction and
statistical comparisons, to final reporting. All calculations performed on the data undergoing
audit were checked.

17


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Chapter 5
Statistical Methods

The following statistical methods were used to reduce and generate results for the performance
factors.

5.1 Minimum Detection Limit

The MDL is defined as the smallest concentration at which the monitor's expected response
exceeds the calibration curve at the background reading by two times the standard deviation (j J
of the monitor's background reading, i.e.,

MDL = 2i.

O

5.2 Linearity

Both concentration and source strength linearity were assessed by linear regression with the
certified gas concentration as independent variable and the monitor's response as dependent
variable. Linearity was assessed in terms of the slope, intercept, and correlation coefficient of the
linear regression.

y = mx + b

where _y is the response of the monitor to a target gas, x is the concentration of the target gas in
the gas cell, m is the slope of the linear regression curve, and b is the zero offset.

5.3 Accuracy

The relative accuracy (A) of the monitor with respect to the target gas was assessed by

T-R
A = — x 100
R

where the bars indicate the mean of the reference (R) values and monitor (7) results.

18


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5.4 Precision

Precision was reported in terms of the percent RSD of a group of similar measurements. For a set
of measurements given by T\, T2,Tn, the standard deviation (j ) of these measurements is

O =

1

n -1

ii

'L(Tt-fy

k= 1

1/2

where T is the average of the monitor's readings. The RSD is calculated from

RSD =

x 100

and is a measure of the measurement uncertainty relative to the absolute value of the
measurement. This parameter was determined at one concentration per gas.

5.5 Interferences

The extent to which interferences affected MDL and accuracy was calculated in terms of
sensitivity of the monitor to the interferant species, relative to its sensitivity to the target gas, at a
fixed path length and integration time. The relative sensitivity is calculated as the ratio of the
observed response of the monitor to the actual concentration of the interferant. For example, a
monitor that indicates 26 ppm of cyclohexane in air with an interference concentration of
100 ppm of carbon dioxide indicates 30 ppm of cyclohexane when the carbon dioxide con-
centration is changed to 200 ppm. This would result in an interference effect of (30 ppm -
26 ppm)cyclohexane/(200 ppm - 100 ppm)C02 = 0.04 or 4% relative sensitivity.

19


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Chapter 6
Test Results

The results of the verification test of the SafEye 227 are presented in this section, based upon the
statistical methods shown in Chapter 5. The monitor was challenged with methane; with pro-
pane; and with a mixture of methane, propane, and ethane over path lengths of 40 to 130 meters,
which are typical path lengths for this monitor. These gases were chosen because they are repre-
sentative of gases monitored by this monitor. Test parameters included MDL, linearity, accuracy,
precision, and the effects of atmospheric interferants on concentration measurements.

6.1 Minimum Detection Limit

The MDL was calculated from measurements in which there were no target gases in the gas cell,
but the monitor analyzed the absorption spectra for the presence of a target gas. The data used to
determine the MDL were obtained under several experimental conditions, including different
path lengths and integration times, as shown in Table 6-1. Table 6-2 shows the results of the
MDL calculations.

The results in Table 6-2 show that the SafEye 227 has an MDL of between 0.003 and
0.012 LEL*m for methane, 0.001 and 0.008 LEL*m for propane, and 0.001 and 0.008 LEL*m
for the mixture of methane, propane, and ethane at the path lengths and integration times tested.
Changing the integration times from 1 to 5 minutes reduced the MDL, but changing the path
lengths between 40 and 65 meters had little consistent effect on the MDL.

6.2 Linearity

6.2.1 Source Strength Linearity

Table 6-3 shows the results from this evaluation of source strength linearity, and Figure 6-1
shows a plot of the effect that the light signal level has on the monitor's measurements. In
Table 6-3, the relative signal power is the measure of light attenuation during that measurement.
For example, a relative signal power of 0.79 means that the light level for that test is 79% of
what the light level is during normal operating conditions. The methane concentration is the con-
centration of gas being delivered to the gas cell during the measurement, and the monitor

20


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Table 6-1. Minimum Detection Limits Data for the SafEye 227

Methane	Propane	Mixture #1

Path Length (m)	Path Length (m)	Path Length (m)

40	40	65 40 40 65 40 40 65

Measure-

Integration Time (min)

Integration Time (min)

Integration Time (min)

ment

1

1

1

1

5

1

1

5

1

Number







Concentration (LEL*m)







1

-0.001

0.010

0.000

0.005

-0.002

0.000

0.007

-0.002

0.020

2

0.000

0.008

0.000

0.000

-0.002

0.004

0.007

-0.001

0.004

3

-0.001

0.025

0.002

-0.001

-0.002

0.003

0.004

-0.001

0.002

4

0.008

0.007

-0.001

-0.001

-0.002

0.002

0.003

-0.002

0.004

5

0.012

0.005

0.003

-0.002

-0.004

0.008

0.005

-0.002

0.004

6

0.002

0.000

0.000

-0.002

-0.002

0.007

0.008

-0.002

0.003

7

0.007

-0.001

-0.001

-0.004

-0.002

0.008

0.007

-0.002

0.009

8

-0.001

-0.001

0.000

-0.004

-0.004

0.008

0.007

-0.002

0.014

9

0.007

-0.002

-0.002

-0.002

-0.002

0.008

0.005

-0.002

0.008

10

0.014

-0.001

0.000

-0.001

-0.002

0.005

0.007

-0.002

0.007

11

0.009

0.000

0.000

-0.001

-0.002

0.003

0.007

-0.004

0.009

12

-0.002

-0.001

0.002

-0.004

-0.002

0.000

0.007

-0.002

0.009

13

0.003

0.000

-0.001

-0.002

-0.004

0.002

0.003

-0.002

0.004

14

-0.004

-0.002

0.000

-0.002

-0.002

0.009

0.003

-0.002

0.013

15

-0.001

-0.002

-0.001

-0.001

-0.002

0.007

0.002

-0.004

0.007

16

-0.001

-0.002

-0.001

-0.005

-0.004

0.004

0.002

-0.002

0.010

17

0.008

-0.002

0.002

-0.002

-0.002

0.004

0.002

-0.002

0.010

18

0.004

-0.002

0.002

-0.002

-0.004

0.007

-0.002

-0.004

0.005

19

0.007

-0.001

-0.001

0.003

-0.002

0.010

-0.001

-0.002

0.020

20

0.003

-0.001

-0.001

0.000

-0.002

0.009

-0.004

-0.004

0.014

21

-0.001

-0.002

0.008

0.007

-0.002

0.007

-0.001

-0.002

0.019

22

0.007

-0.002

0.004

0.004

-0.002

0.003

-0.001

-0.002

0.012

23

0.008

-0.002

0.005

0.005

-0.004

0.012

-0.004

-0.002

0.004

24

0.009

-0.002

0.012

0.003

-0.002

0.017

-0.004

-0.002

0.008

25

NA

-0.001

0.007

-0.002

-0.002

0.014

-0.002

-0.004

0.010

response is the resulting reading from the SafEye 227. The source strength results show that there
is little degradation in monitor performance during conditions of declining source strength. The
maximum differences between SafEye 227 response and the methane concentration were
0.13 LEL*m at 1.00 LEL*m methane and 0.1 LEL*m at 3.0 LEL*m methane. The data indicate
only a slight effect of source strength on methane measurement, with source reductions of up to
62%. The slopes of the linear regression lines of zero and 0.05, shown in Figure 6-1, indicate that
reducing the source strength had a slightly negative effect on the monitor's response over the
range tested.

21


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Table 6-2. Minimum Detection Limits of the SafEye 227

Target

Path Length

Integration

MDL

Gas

(m)

Time (min)

(LEL*m)

Methane

40

1

0.010

Methane

40

1

0.012

Methane

65

1

0.003

Propane

40

1

0.006

Propane

40

5

0.001

Propane

65

1

0.008

Mixture

40

1

0.008

Mixture

40

5

0.001

Mixture

65

1

0.005

Table 6-3. Source Strength Linearity of the SafEye 227

Relative
Signal Power

Methane Concentration
(LEL*m)

Monitor
Response (LEL*m)

1.00

1.0

0.91

0.79

1.0

0.87

0.57

1.0

0.88

0.38

1.0

0.87

1.00

3.0

2.9

0.79

3.0

2.9

0.57

3.0

2.9

0.38

3.0

2.9

22


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y = 0 .OOx + 2.9
r = 0.90

'• I'.-*.'	.:r: v. m :	

M •:: • .. ¦. i .

LE-V

y = 0.05 + 0.85
r = 0.58

Figure 6-1. Source Strength Linearity Plot of the SafEye 227
6.2.2 Concentration Linearity

Table 6-4 and Figures 6-2 through 6-4 show the results of the evaluation of concentration
linearity. The regression analysis results are shown on the individual figures.

Table 6-4. Concentration Linearity Data for the SafEye 227

Target Gas

Target Gas Concentration
(LEL*m)

Monitor Response
(LEL*m)

Methane

1.0

0.91

Methane

2.0

1.7

Methane

3.0

2.9

Methane

2.0

1.8

Methane

2.0

1.8

Propane

1.0

1.0

Propane

2.5

2.6

Propane

5.0

3.8

Propane

2.5

3.0

ProDane

2.5

3.2

Mixture

0.96

0.9

Mixture

1.9

1.7

Mixture

2.9

2.6

Mixture

1.9

1.7

Mixture

1.9

1.7

23


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Target Gas Concentration (LEL*m)

Figure 6-2. Concentration Linearity Plot of the SafEye 227 Challenged
with Methane

Figure 6-3. Concentration Linearity Plot of the SafEye 227 Challenged
with Propane

24


-------
3,

£

y = 0.83x +
R2 = 0.c

O.D

0.5

1.0

1.5

2.0

2.5

3.0

3.5

Target Gas Concentration (LEL*m)

Figure 6-4. Concentration Linearity Plot of the SafEye 227 Challenged
with Mixture

The results from the concentration linearity test show that the SafEye 227 exhibits linear
behavior for methane and for the gas mixture, with non-linear responses for propane. When
challenged with methane, the monitor had a slope of 0.98 and an r2 value of 0.99. The monitor
had a slope of 0.66 and an r2 value of 0.76 when challenged with propane and a slope of 0.83 and
an r2 value of 0.99 when challenged with the mixture of gases. The monitor responded well to
methane in all cases, considering that the mixture of gases was composed of mostly methane.
The additional gases in the mixture (propane and ethane) may have caused the monitor to change
sensitivity, reflected by the smaller slope of 0.83.

6.3 Accuracy

The accuracy of the SafEye 227 was evaluated at each target gas concentration introduced into
the cell. These concentrations were introduced at the path lengths and integration times shown in
Table 6-5, where the measurement data and relative accuracy results are shown. The accuracy
results compare the monitor response with the target gas concentration as delivered by the
Environics 2020 gas dilution system.

These results show that the SafEye 227 had a relative accuracy of between -3.8 and -13% for
methane, -23 and 28% for propane, and -6.5 and -12% for the mixture of gases. The results also
show that the monitor is most accurate when challenged with methane. The mixture of gases,
composed mostly of methane, deviated the most from the expected value, but it consistently

25


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Table 6-5. Results of Accuracy Tests for the SafEye 227



Target Gas



Integration

Monitor

Relative



Concentration

Path Length

Time

Response

Accuracy

Gas

(LEL*m)

(m)

(min)

(LEL*m)

(%)

Methane

0.99

40

1

0.907

-8.4

Methane

2.0

40

1

1.74

- 13

Methane

3.0

40

1

2.88

-3.8

Methane

2.0

130



1.78

- 10

Methane

2.0

65

1

1.85

-6.7

Propane

1.0

40

1

0.958

-4.2

Propane

2.5

40

1

2.57

2.9

Propane

5.0

40

1

3.85

-23

Propane

2.5

130



3.02

21

Propane

2.5

65

1

3.20

28

Mixture

0.96

40

1

0.898

-6.5

Mixture

1.9

40

1

1.69

- 11

Mixture

2.9

40

1

2.55

- 12

Mixture

1.9

130

5

1.73

-9.0

Mixture

1.9

65

1

1.71

- 10

deviated in the same direction and by the same magnitude, suggesting a possible scale factor or
responsiveness error. If caused by the presence of propane and ethane in the mixtures, the effect
of these gases on SafEye response must be strong, given the low proportions of these gases in the
mixtures.

The SafEye 227 has four built-in calibrations, each one for a different target gas. These cali-
brations settings are for pure methane, pure propane, and two general hydrocarbon mixtures. The
mixed gas calibrations used for the test unit were based on a gas mixture of 92% methane, 4%
propane, and 4% ethane. The actual mixture used during the test differed from this calibration
setting. Given the fact that the monitor's setting did not exactly match the gas being used, the
accuracy results for the mixture gas were expected by the vendor.

6.4 Precision

Precision data were collected during measurement #9 (see Table 3-2) using an integration time of
1 minute and a path length of 40 meters. The target gas was introduced into the gas cell at a
concentration of 3 LEL*m for methane, 5 LEL*m for propane, and 4.5 LEL*m for the mixture of
gases. Twenty-five successive analyses were made for the target gas. The data from these
measurements are found in Table 6-6, and the results are shown in Table 6-7.

26


-------
Table 6-6. Data from Precision Tests on the SafEye 227







Target Gas





Methane



Propane

Mixture

Analysis #

(LEL*m)



(LEL*m)

(LEL*m)

1

2.90



3.83

2.56

2

2.90



3.83

2.55

3

2.88



3.86

2.55

4

2.90



3.87

2.54

5

2.87



3.85

2.55

6

2.89



3.88

2.55

7

2.89



3.88

2.54

8

2.90



3.86

2.55

9

2.90



3.87

2.55

10

2.90



3.90

2.55

11

2.90



3.87

2.54

12

2.90



3.88

2.53

13

2.87



3.87

2.54

14

2.89



3.89

2.55

15

2.88



3.89

2.54

16

2.89



3.91

2.54

17

2.90



3.89

2.54

18

2.90



3.93

2.53

19

2.89



3.91

2.53

20

2.88



3.93

2.53

21

2.89



3.90

2.54

22

2.90



3.89

2.54

23

2.90



3.90

2.54

24

2.87



3.92

2.54

25

2.89



3.92

2.54

Table 6-7. Results of Precision Tests on the SafEye 22T



Gas Cell



Standard





Concentration Average Monitor Deviation

Relative Standard

Target Gas

(LEL*m) Response (LEL*m) (LEL*m)

Deviation (%)

Methane

3.0

2.89

0.010

0.340

Propane

5.0

3.89

0.027

0.705

Mixture

4.6

2.54

0.008

0.326

integration time = 1 minute; path length = 40 meters.

27


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These results show that the methane data had an RSD of 0.340%, propane data had an RSD of
0.705%, and the gas mixture data had an RSD of 0.326%. The magnitude of these values shows
that the monitor performed very consistently over the 25 minutes required for this measurement.
In addition, the similarity of the RSD values to each other shows that the monitor performs
consistently while analyzing for the three target gases.

6.5 Interferences

Interference tests of the SafEye 227 evaluated the effects that the common atmospheric inter-
ferants water and carbon dioxide have on the monitor's ability to determine the concentration of
the target gases and on the MDL for the target gases. Both water and carbon dioxide have
absorption features in the same infrared region that the SafEye 227 uses to analyze for the target
compounds. Because the concentration of these two potential interferants is usually much greater
than the concentration of the compounds of interest, the presence of water and carbon dioxide
can make analyzing for the target compounds difficult. IR monitors use various methods to deal
with these interferants, and this test evaluated the effectiveness of the SafEye 227's methods.
Tables 6-8 and 6-9 show the data used to determine the interference effect of water and carbon
dioxide on the concentration and MDL determination, respectively.

As shown in Table 6-8, changing the total number of water and carbon dioxide molecules in the
path length had little effect on the monitor's ability to accurately calculate the concentrations of
the target gas. Overall, carbon dioxide and water levels had no consistent effect on relative
accuracy for the three gases.

Table 6-8. Concentration Data from Interference Tests on the SafEye 227



Path

Concentration

Concentration

Target Gas

Monitor

Relative



Length

of C02

of H20

Concentration

Response

Accuracy

Target Gas

(m)

(DDm*m)

(DDm*m)

(LEL*m)

(LEL*m)

(%)

Methane

40

1.38E+04

5.80E+03

2.0

1.74

-13

Methane

65

2.51E+04

6.39E+03

2.0

1.85

-6.7

Methane

130

4.76E+04

1.10E+04

2.0

1.78

-10

Propane

40

1.67E+04

7.40E+03

2.5

2.57

+2.9

Propane

65

2.63E+04

7.77E+03

2.5

3.20

+28

Propane

130

5.33E+04

2.13E+04

2.5

3.02

+21

Mixture

40

1.49E+04

4.76E+03

3.1

1.69

-45

Mixture

65

2.58E+04

8.89E+03

3.1

1.71

-44

Mixture

130

4.82E+04

9.99E+03

3.1

1.73

-43

28


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Table 6-9. MDL Data from Interference Tests on the SafEye 227



Path









Length

Concentration of C02

Concentration of H20

MDL

Target Gas

(m)

(ppm*m)

(ppm*m)

(LEL*m)

Methane

40

1.88E+04

4.44E+05

0.010

Methane

40

1.46E+04

5.27E+05

0.012

Methane

65

2.44E+04

9.06E+05

0.003

Propane

40

1.73E+04

4.81E+05

0.006

Propane

40

1.68E+04

5.00E+05

0.001

Propane

65

2.60E+04

8.59E+05

0.008

Mixture

40

1.50E+04

5.41E+05

0.008

Mixture

40

1.68E+04

5.15E+05

0.001

Mixture

65

2.58E+04

7.85E+05

0.005

Table 6-9 shows that changing the total number of water and carbon dioxide molecules in the
path length also had little effect on the monitor's MDL for the target gas; no consistent impact of
water and carbon dioxide levels on MDLs was found.

6.6 Other Factors

6.6.1	Costs

The cost of the SafEye 227 ranges, as tested, from $6,000 to $10,000, according to Spectrex,
depending upon application.

6.6.2	Data Completeness

All portions of the verification test were completed, and all data that were to be recorded were
successfully acquired. Thus, data completeness was 100%.

29


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Chapter 7
Performance Summary

The SafEye 227 MDL for the three gases tested ranged between 0.003 and 0.012 LEL*m for
methane, between 0.001 and 0.008 LEL*m for propane, and between 0.001 and 0.008 LEL*m
for the mixture. While variation in detection limits can be caused by the changes in path length,
no consistent trend was found when changing path length. However, increasing the integration
time from 1 to 5 minutes reduced the MDL.

The tests of the effects of source strength on the ability of the monitor to measure methane
showed that there was little to no degradation of monitor performance, with source strength
reductions of up to 62%. Near zero slopes for both the 1 and 3 LEL*m tests showed that reducing
source strength had little effect.

The concentration linearity results showed that the SafEye 227 had a regression slope of 0.98 and
an r2 value of 0.99 for methane, a regression slope of 0.66 and an r2 value of 0.76 for propane,
and a regression slope of 0.83 and an r2 value of 0.99 for the mixture, each over a range of 1 to
5 LEL*m.

The SafEye 227 had a relative accuracy of between -3.8 and -13% for methane, -23 and 28% for
propane, and -6.5 and -12% for the mixture of gases.

Precision results showed that methane data had an RSD of 0.340%, propane data had an RSD of
0.705%, and the mixture data had an RSD of 0.326%. This RSD was calculated at one experi-
mental condition using a path length of 40 meters, an integration time of 1 minute, and a con-
centration of 3 LEL*m for methane, 5 LEL*m for propane, 4.5 LEL*m for the mixture of gases.

Analysis of the effects of the interferences of water and carbon dioxide on the measuring ability
of the SafEye 227 showed that neither the accuracy nor the MDL were affected consistently by
the changing concentrations of water and carbon dioxide in the atmosphere. Variations in MDL
and relative accuracy were similar to those found during other measurements made under normal
operating conditions, and no consistent interference effect could be inferred.

30


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Chapter 8
References

1.	Test/QA Plan for Verification of Optical Open-Path Monitors, Battelle, Columbus, Ohio,
October 28, 1999.

2.	Compendium Method TO-16 Long-Path Open-Path Fourier Transform Infrared Monitoring
of Atmospheric Gases, EPA-625/R-96/010b, U.S. Environmental Protection Agency,
Cincinnati, Ohio, January 1999.

3.	Combustion, Appendix E, Irvin Glassman, 1987.

4.	Quality Management Plan (QMP) for the ETV Advanced Monitoring Systems Pilot,

Version 2.0, U.S. EPA Environmental Technology Verification Program, Battelle,
Columbus, Ohio, October 2000.

31


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Appendix A
Data Recording Sheet

A-l


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ETV - Spectrex, Inc

Etv Advanced Monitoring Systems Pilot Verification of Optical Open Path Monitor Round Two

Meas. # (From tesWA plan Table 'i'f1:	



Cell Temp

Int. Time

Vendor; Spectrex, Inc.

(F):

(min):

Iristru merit

C02 Cone.

Pathlength

Mode!:

(ppm):

(meters):

Battelle, West Jefferson,

Ambient RH

Cell Length

Location: Ohio

(%)¦

(cm):

Vendor

Ambient



Operator: Jay Cooley

Temp (F):

Sample Gas:



ozone uoric.



Time:

(ppb):

Sample Gas





Cone, in Ceil

Date:



(ppm):

Data Point #

Meas. Result
(voits)



Note: Measurement #s (3,4,5,10,11&12
only)

1





Neutral



Mon itor

2





Density Filter

Desired

response
(volts)

3





#

Attenuation

4





none

0



5





1

20%



6





2

40%



7





3

60%



8





none

o



9







10







11







12







13







14







15







16







17







18







19







20







21







22







23







24







25













Data taken by:

Date:





Data reviewed by:

Date:





data sheet.xls

A-2


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