United States
Environmental Protection
Agency
Environmental Monitoring Systems
Laboratory
Research Triangle Park NC 27711
Research and Development
EPA/600/S4-85/012 Mar. 1985
Project Summary
Field Experience with Four
Portable VOC Monitors
Robert A. Ressl and Thomas C. Ponder, Jr.
This report discusses the field opera-
tion problems associated with use of
four portable volatile organic compound
(VOC) detection instruments in con-
ducting Reference Method 21 VOC
screenings. The report presents the
results of the field trials and summarizes
the ease of use of each instrument.
Information on operational problems
and recommendations are provided.
Also included are discussions of the
features that would make all portable
instruments more reliable, durable, or
convenient to use. Based on the data
collected for this study, three of the
instruments report similar leak rates in
the facility where they were used.
This Project Summary was developed
by EPA's Environmental Monitoring
Systems Laboratory, Research Triangle
Park, NC, to announce key findings of
the research project that is fully docu-
mented in a separate report of the same
title (see Project Report ordering in-
formation at back).
Introduction
The U S. Environmental Protection
Agency (EPA) has issued performance
standards and guidelines to limit emis-
sions of volatile organic compounds (VOC)
from several stationary source categories.
These industries such as petroleum re-
fineries, synthetic organic chemical
plants, and natural gas processing plants
emit significant quantities of VOCs from
sources other than classical point sources
into the workplace and surrounding at-
mosphere. These fugitive VOC emissions
occur from valves, pumps, drains, pres-
sure relief devices, etc.
As described in 40 CFR 60, Appendix A,
Reference Method 21 (RM 21), Deter-
mination of Volatile Organic Compound
Leaks, there are technically feasible
devices suitable for monitoring fugitive
VOC leaks. These devices can be placed
near possible points of emissions and will
respond to releases of the organic com-
pounds. Specific instruments suitable for
this purpose include, but are not limited
to, catalytic oxidation, flame ionization,
infrared absorption, and photoionization
detectors.
Subsequent "field use of portable VOC
detectors has disclosed some instrument-
specific problems such as undetected
flame-outs, plugged orifices from dirt,
high background readings due to chem-
ical absorption on probe and tubing
surfaces, high humidity effects, varying
or lack of response, long response times,
and calibration drift. To identify and
document these types of problems, four
monitors were used to conduct screening
following RM 21 procedures.
This report provides basic information
on each instrument, howthey were used,
what operational problems were encount-
ered during and between screenings, and
the ease of use of each instrument in
relation to the other three. Special atten-
tion was given to documenting opera-
tional problems and ease of use.
Field Trial Methods
The following VOC analyzers were
used during the study
• Foxboro Century Systems Portable
Organic Vapor Analyzer Model OVA-
108
• UnitedTechnology'sBacharach Instru-
ments Model TLV Sniffer*
• Analytical Instruments Development,
Inc., AID Model 712*
• HNu Systems, Inc., Model PI-101
"Registered Trademark
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The instruments used represent three
types of detectors. The OVA and Analyt-
ical Instruments Development, Inc., Mod-
el 712 (AID) are flame mnization detec-
tors(FID). UmtedTechnology's Bacharach
Instruments, Inc., Model TLV Sniffer
(TLV) uses catalytic oxidation. The HNu
Systems, Inc., Model PI-101 (HNu) uses a
photoionization detector (PID).
A comparison of the manufacturers'
published specifications was made with
the RM 21 requirements. Although some
of the instruments did not appear to meet
the RM 21 requirements, all the instru-
ments were used and their field exper-
ience reported. No attempt was made to
make a rigorous evaluation of each
instrument or of RM 21. However, where
possible, the requirements of RM 21
were met.
Two types of operational tests were
conducted with the equipment—a reli-
ability check and field operations. In the
reliability check the instruments were
charged and allowed to operate for sever-
al 8-hour periods. This test provided some
assurance that the instruments could
operate over an 8-hour period. In the field
operations all four instruments were
used to screen a series of 200 to 300
sources. Following the screening, the
instrument operator completed an evalua-
tion sheet, reported any problems with
the instrument, and provided general
subjective comments on the instrument
as a leak detection tool. Screening was
conducted at two petroleum refineries, a
chemical manufacturing plant, and a
natural gas processing facility.
Summary of Evaluations
The field trials were designed to provide
subjective comments on the instruments'
performances Table 1 summarizes the
comments developed from the screen-
ings.
All the instruments except the HNu
were equipped with some kind of probe
filter, and these filters were always
installed. However, a 2-inch length of
plastic tubing loosely stuffed with glass
wool was added to protect the probe from
contamination by the greases and oils
present at many sources. The instru-
ments' responses were the same with
and without the plastic tubing in place.
The tubing is easily replaced and reduces
time spent in the field cleaning the metal
sample probes. The tubing was normally
replaced on an as-required basis which
was fairly frequently. The replacement
criteria was based on appearance of the
tubing. If there was any visible contam-
ination on it, it was replaced.
The TLV comes without a shoulder
strap making it very awkward to use for
screening. Also, since the zero knob is
easily moved, a piece of tape was used to
secure it. This prevented having to con-
stantly check and reset the instrument
zero.
The OVA comes with one strap. How-
ever, after several screenings it was
realized that if worn as a backpack it
would be easier to use, make the operator
more mobile, and speed up the screen-
ings. Therefore, a second strap was
purchased from the manufacturer so that
the OVA could be worn as a backpack,
using the two carrying straps as a shoul-
der harness. Since the OVA has a readout
on the hand-held probe, this did not
create any problem. However, when the
instrument flamed out, relighting it was a
little awkward since the operator had to
either get someone else to press the
igniter button on the case or let the case
slip forward on the shoulders and stretch
around to reach it.
Desirable Instrument
Features and
Recommendations for
Future Studies
The desirable features that should be
included in a field screening instrument
are as follows:
• The strap should allowfor carrying the
instrument on the back, out of the way,
leaving the hands free for climbing,
handling log sheets, and manipulating
the probe and readout (assuming the
readout is attached to the probe).
• The calibration controls should be
located in the backpack and protected
by the instrument case cover. All
controls should have locks to prevent
unintentional movement.
• The readout should be analog and use
a logarithmic scale that ranges from
10 to 100,000 ppm. RM 21 must be
modified to accept the resulting scale
divisions.
• The readout should have a lock-and-
hold reading capability and/or hold-
highest-reading function switch.
• There should be provisions to use the
instrument as a go/no-go detector
with indicator lights to show whether
the reading is above or below the
calibration point.
• An igniter button should be located on
the probe/readout if the instrument
uses an FID.
• A series of status indication lights
should appear on the probe/readout
assembly to show if the instrument
has sufficient battery charge and if it is
responding.
• The sample line connecting the back-
pack and probe/readout should be at
least 4 feet long and very flexible.
• A holster should be provided for the
probe/readout so that both hands can
be free for climbing and handling data
sheets.
• The probe assembly should have pro-
visions for frequent cleaning because
the probe becomes contaminated with
grease and other materials during the
screening process.
• The system should be protected from
the elements and be able to operate in
light rain, high humidity, and high
ambient temperatures.
• The system should protect the recharge-
able battery from overcharging and
deep discharge. Provisions should be
made for easy battery removal and
replacement. Ideally, the charging
system should be capable of being left
on charge at all times. There should
also be an indication of when the unit
is within one hour of being too weak to
operate effectively. This would provide
time to check the instrument calibra-
tion before the unit required recharg-
ing.
• The calibration system should allow
for easy calibration to multiple calibra-
tion gases
Available and additional data on leak
rates, repeatability of screening values,
and responsefactorsforVOC instruments
should be assembled in a screening hand-
book to present the kinds of information
necessary for a proper screening pro-
gram. Information should be included on
how to screen various types of sources,
how to prepare log and repair sheets,
response factors of various instruments,
lists of typical compounds encountered in
various types of facilities, etc. Screening
procedures should be developed for organ-
ic materials with response factors greater
than 10.
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Table 1. Summary of Operating Problems
Item OVA
TLV
HNu
AID
Carrying strap
Battery
Battery charger
Instrument readout
The best arrangement of
the instruments evalu-
ated.
Acceptable during
period of evaluation.
Acceptable during
period of evaluation
The analog readout
with logarithmic scale
was conveniently lo-
cated in the probe and
very easy to use.
No strap; instrument
was earned by a handle
that was sometimes
inconvenient
Acceptable during
period of evaluation
Acceptable during
period of evaluation
The readout in the con-
trol unit was less con-
venient to read than on
the probe but was
acceptable It
required frequent scale
changes that were some-
what inconvenient.
The strap was very nar-
row and after an hour
of carrying was quite
uncomfortable
Acceptable during
period of evaluation
Acceptable during
period of evaluation.
The readout in the con-
trol unit was less con-
venient to read than on
the probe but was
acceptable. It
required frequent scale
changes that were some-
what inconvenient
The strap was unpadded
and, although reasonably
wide, the edge of the
strap became very uncom-
fortable after an hour
of carrying.
Acceptable during
period of evaluation
Acceptable during
period of evaluation
The digital readout was
difficult to read from
an angle, and the fre-
quency with which it had
to be updated made selec-
tion of a reading value
difficult
Calibration knob
or zero/span
adjustment
On/off and other
controls
Sample line and
instrument
umbilical
The knob could not be
secured. However,
since it was located on
the control module,
which had a cover, it
did not require secur-
ing.
The controls are on the
control module. The
instrument and pump
switches are easily
moved (newer models
have locking toggles).
The handles on the
hydrogen supply are
too short (newer
models have longer
ones} The gas select
knob was not used
since span gases were
used for calibration
The sample line tends
to kink after long use
when the protective
sleeve slips. The line
could be longer. The
electrical connector at
the control module has
been weakened and has
shorted
The zero adjust knob
(only adjustment) was
located on the control
module and could not be
secured. It was easily
and frequently bumped,
requiring re-zeroing of
the instrument, until
it was secured with
tape.
The on/ofl'/standby,
battery, operate, and
range switch caused
no problems
The sample hose could
be longer During the
evaluation period, the
hose developed a kink
and would frequently
pinch off, causing the
pump to stall and the
instrument to operate
improperly
The zero knob was some-
what protected and was
quite stiff to turn.
It is located on the
control module and did
not require securing.
The controls were
acceptable.
The umbilical was too
sh'prt.
The calibration (zero
and span) require a
screwdriver to adjust
The response and level
knobs had locks to
secure them. All were
acceptable.
The alarm, on/off switch,
and the battery/AC/charge
switch were frequently
confused, which resulted
in turning off the
instrument instead of the
audible alarm on several
occasions.
The umbilical was too
short.
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Table 1. (Continued)
Item
OVA
TLV
HNu
AID
Probe contamination
Probe assembly
Audible alarms
Screening time
Since all the plants had
some sources where the
probe could get dirty, all
units were affixed with a
2-in. long piece of Tygon
tubing with a glass wool
plug as a primary filter.
This flexible tip was also
helpful when screening
because it made it easier
to get the probe tip close
to the source interface.
The assembly was con-
veniently sized and not
uncomfortably heavy.
The alarm adjust knob
on the back was broken
off when the assembly
was dropped.
The alarm cannot be
heard in most plant
environments. The ear
plug was very uncom-
fortable and the oper-
ators did not wear it.
See OVA comments.
See OVA comments.
See OVA comments.
Very good:
per source.
-30 seconds
The probe is very
lightweight and easy
to manipulate
The assembly was quite
heavy and very diffi-
cult to manipulate.
See OVA comments
Not Applicable.
The assembly had a com-
fortable feel. How-
ever, the plastic bezel
damaged during the
second screening falls
off frequently.
See OVA comments
Somewhat slow; —45
seconds per source
Unknown; no response
to sources.
Very good; ~30 seconds
per source.
U. S. GOVERNMENT PRINTING OFFICE:1985/559 019/10796
-------
Robert A. Ressl and Thomas C. Ponder, Jr., are with PEI Associates, Inc.,
Arlington. TX 76012.
Roosevelt Rollins is the EPA Project Officer (see below).
The complete report, entitled "Field Experience with Four Portable VOC
Monitors," (Order No. PB85-165 496/A S; Cost: $ JO. 00, subject to change) will
be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Environmental Monitoring Systems Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
Penalty for Private Use $300
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