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Photograph of a Drager hand pump used to measure carbon dioxide levels in the environment. Guide to Toxic Gas Measurement Instruments & Gas Detector Tubes for Indoor Gas Level Tests

  • GAS DETECTION INSTRUMENTS - CONTENTS: Recommendations for gas measurement instruments, gas detector tubes, Draeger & Gastec, Komyo Rikagaku Kitagawa, RAE, & Sensidyne gas detection tubes & pumps for detection of gases - Warnings about using instruments of any kind for detection of toxic gase
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Types of test instruments for detecting or measuring the level of toxic or dangerous gases in buildings:

This document discusses tools and methods used to test for the level of toxic and other gases in buildings and in outdoors. In related documents we give references and explanation regarding toxicity of several of the most common indoor gases, based on literature search and obtained from the U.S. government and expert sources.

This text may assist readers in understanding these topics. However it should by no means be considered exhaustive. Seek prompt advice from your doctor or health/safety experts if you have any reason to be concerned about exposure to toxic gases.



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Tools and methods for detecting or measuring the level of gases in buildings or outdoors

TIF 8800 combustible gas analyzer checking a furnace draft hood for spillage (C) Daniel FriedmanWhile other methods are available for gas detection in or around buildings, (such as eletronic gas detection equipment giving gas level readings in ppm and vacuum canisters for lab analysis) the two most common methods used by building inspectors and trades people for sensitive detection of problem gases in buildings are broad spectrum combustible gas analyzers such as
the TIF 8800 GAS DETECTOR,
and
specific gas analyzers for halogens such as
the TIF 5000 GAS DETECTOR, and calibrated gas pumps using colorimetric gas detection tubes discussed here.

The companies that provide pump and tube gas detection systems produce a very wide range of very sensitive calibrated gas detection tubes, all of which will work just fine with a single, volume-calibrated pump that draws the air or gas sample through the tube. Color changes and a scale marked on the gas detection tube give a nearly instant reading of the target gas level in the area tested.

Watch out: while a gas detection instrument may itself be highly sensitive and very accurate, variations in building condtions can cause a gas to be present at times and below the limit of detection at other times. Therefore when a gas detection test gives negative results (no gas detected) you should not rely on that result alone if there is a risk of unsafe conditions. For example
see CARBON MONOXIDE - CO poisoning.

Toxic or Hazardous Gas Detection using Calibrated Pump and Gas Detection Tubes

TIF 5000 refrigerant gas leak detector for halogensThe photograph at the top of this page shows a Sensidyne gas detection hand pump which currently (2008) uses KitagawaTM gas colorimetric gas detection tubes to measure the level of gases in a building. Here we were checking the level of carbon monoxide (CO) at a heating system.

Above is the TIF 8800 GAS DETECTOR in use at a gas furnace draft hood, and at left is

the TIF 5000 GAS DETECTOR used for refrigerant gas detection including detection of refrigerant gas as a tracer gas if used to check for heat exchanger leaks - something no longer recommended nor permitted where discharge of refrigerants to the environment is a possibility.

We like the Sensidyne gas pump method because one or two strokes can produce an accurate quantitative measurement of the level of gas in the area with minimum manipulation of the pump by the inspector.

However indoor air quality investigators and others having need to measure concentrations of various gases in indoor or outdoor air also make very frequent use of the Draeger gas pump and Drager colorimetric gas detection tubes which we describe below, or Gastec Gas Sampling Pumps using gas detection tubes sold by GasTecTM.

Safety note: It is critical that the proper pump and gas detection tube combination be used as gas detection tubes are calibrated to work with particular gas pumps. Using the wrong pump or gas detection tube risks making inaccurate gas measurements - an error which could be fatal in some circumstances.

All of these gas detection systems use a similar approach for measuring the level of gases in a building. The Drager system uses a rubber bellows pump which requires more pump strokes than the Sensidyne pump (shown above) but may provide a wider range of detector tubes and gas sampling approaches.

For use by firefighters and fire investigators, Draeger also provides a special manifold which permits multiple samples to be collected simultaneously to screen for a very wide range of toxic gases which may be present at a fire scene.

Watch out: be sure to read GAS DETECTOR WARNINGS .

Warning: About Selecting the Proper Gas Detection Tube

Gas Tube and Gas Pump Must be Compatible? Some authors report some gas detection tube interchangeability.

Gas tube testing pump schematic (C) Daniel FriedmanColorimeteric gas detection tubes produced by different manufacturers are not necessarily interchangeable among gas detection pumps

Be sure that the gas detection tube you are using is one recommended for use with your gas detection pump - check both the gas detection pump manufacturer's instructions and the gas detection tube manufacturer's specifications.

Watch out: we were informed in May 2008 by Nextteq GastecTM detection tube distributor in the U.S., Gastec tubes that are currently available are not intended for use on the SensidyneTM gas detection pump.

At one point in time, Sensidyne had the contract for Gastec tubes and lost it due to rebranding.  The tubes they sell now are Kitagawa tubes, not Gastec.  We don't want to confuse anyone out there that they can use a Gastec tube with the Sensidyne pump.  The Gastec tubes are not calibrated to work with a Sensidyne pump and therefore, the reading could be incorrect and prove fatal in some cases.

Really? Haag (2001) stirred a hornets' nest of marketing and technical issues, claims, counter-claims when he reported:

Both pump flow profiles and test gas measurements demonstrate that three piston hand pumps in common use (RAE Systems LP-1200, Sensidyne/Gastec GV/100, and Matheson-Kitagawa 8014-400A) are fully interchangeable.

Two bellows pumps (Draeger Accuro and MSA Kwik-Draw) also are interchangeable with each other.

Mixing of bellows and piston systems is often possible, but there are enough exceptions to conclude that such practice should be discouraged because it can lead to inaccurate readings and thus potentially dangerous overexposures.

For an example of a family of gas detection instruments & pumps capable of detecting an enormous range of specific gases and providing a measurement of gas concentration in air including pumps that use a colorimetric gas detection tube
see Dräger GAS DETECTORS.

There you will note that Hirsh (2001) vigorously objected to Haag's report, calling it marketing propaganda, and noted that Draeger as well as various agencies do not support interchangeability of gas detection tubes.

Gas Tube Must Be Properly Sensitive to the Gases Being Investigated

Bulb type gas detector tube pump (C) InspectApediaWatch out: Be sure to select gas detection tubes designed to detect the proper gases being screened in a building, and also to select the gas detector tube which is calibrated to detect gases at the proper level of concern.

The detection of many gases is supported at varying levels of sensitivity.

Selecting a tube which is not sensitive enough may result in failing to detect the presence of the target gas. Selection of a gas detection tube which is too sensitive may result in inability to accurately detect the actual level of gas which is present since the tube will become saturated before the actual gas level has been recorded.

Watch out: in our OPINION using a simple bulb-type pump with a gas detector tube (illustration above) as has been suggested in some older gas detection articles is a bad idea: if one cannot be confident that each depression of the bulb produces an accrate and known gas volume the quantitative measurement of gas concentrations given by the detector tube would be simply nonsense.

For a separate example of test kits & gas detection instruments focused on a specific gas
see FORMALDEHYDE GAS TEST KITS, METERS.

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Continue reading at GAS EXPOSURE LIMITS & STANDARDS or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.

Or see CONVERT PPM to % CONCENTRATION To convert between % and ppm

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