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Guide to Toxic Gas Measurement Instruments & Gas Detector Tubes for Indoor Gas Level Tests InspectAPedia®  -     Recommendations for gas measurement instruments, gas detector tubes, Draeger & Gastec, Komyo Rikagaku Kitagawa, RAE, & Sensidyne gas detection tubes & pumps for detection of gases Use of a Drager pump or Sensidyne pump and colorimetric gas detection tubes How Colorimetric gas detection tubes work Using the TIF 8800 Gas Detector & pocket-sized gas detectors for combustible and heating flue gases Guide to using the TIF 5000 Gas Detector for air conditioning and refrigerant gas leaks Warnings about using instruments for detection of toxic gases

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. © Copyright 2010 Daniel Friedman, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use links at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.

© Copyright 2010 Daniel Friedman, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use links at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.

Recommendations for tools and methods for detecting gases in buildings or outdoors

The photograph at the top of this page shows a Sensidyne gas detection hand pump which currently (2008) uses Kitagawa^TM 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.

We like this gas pump method because one or two strokes can produce an accurate 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 GasTec^TM.

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. Details are in this article at Warnings.)

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.

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CARBON MONOXIDE - CO
CARBON DIOXIDE - CO₂
OXYGEN - O₂
GAS MEASUREMENT TOOLS
  Use of a Drager pump
  How Colorimetric gas detection tubes work
  Using the TIF 8800 Gas Detector
  Using the TIF 5000 Gas Detector
  Warnings re instruments for detection of gases
  Warning: choose the right tube for gas detection

• Jennifer Moore, Sales Administrator, Nextteq, LLC, Tampa FL, www.nextteq.com 813-249-5888. Nextteq is the master Distributor for Gastec in the United States. According to the company's website, Gastec Gas Sampling Pumps are the industry’s first and only pumps to provide on-the-spot measurement of ambient temperature. [Private email, JM to DF 5/23/08]
• "Choosing and Using a Carbon Monoxide CO Monitor," Dan Friedman, The ASHI Technical Journal, Vol. 2 No. 1, July1991
• "Heat Exchanger Testing, Who's Right?" Dan Friedman, The ASHI Technical Journal, Vol. 2 No. 1, July1991
• "Case History: LP Gas Leak - Using the TIF 8800," Dan Friedman, The ASHI Technical Journal, Vol. 2 No. 1, July1991
• Chimneys, Flues, Woodstoves & Fireplaces: Safety Concerns, safe and proper venting of combustion gases, carbon monoxide hazards
• Critique, contributions wanted: Contact Us to suggest text changes and additions and, if you wish, to receive online listing and credit for that contribution.

An Example of Use of a Drager pump and Drager Colorimetric Gas Detection Tube (to measure the level of CO₂)

Here is our Draeger bellows-type gas sampling pump. This instrument accepts a remarkably wide range of colorimetric gas detection tubes offered by Drager, and includes a counter to count pump strokes.

The photo below shows a Drager colorimetric gas detection tube (also called a "color detector tube") used to test levels of a very wide range of specific gases in air. In an indoor air test (in our laboratory) this particular detector was not being used to measure oxygen, but rather carbon dioxide.

As the blue-stained portion of the tube shows, this tube detected that the CO₂ level was about 600ppm which is typical of indoor air and is an acceptable and safe level.

Colorimetric gas detection tubes and how they work

Colorimetric gas detection tubes such as those sold by Drager (or Draeger), Gastec, (two that we use predominantly) and by Kitagawa, and pumps from Drager, Gastec, Komyo Rikagaku Kitagawa, and RAE all work on a similar principle: a measured volume of gas (or air) is drawn through a tube which contains chemicals which change in color in response to the presence of a specific target gas (or range of gases) present in the sample.

By knowing the volume of gas or air sampled, the amount of color change read on a linear scale on the colorimetric gas detection tube can be translated into a very accurate measurement of level of gas present, described in percentage of the total air or in parts per million (PPM).

How a Colorimetric gas detector tube is used

Colorimetric gas detection tubes are sold and distributed in the U.S., Latin America, Asia, and Europe primarily by

• Drager (or in some spellings and literature, Draeger),
• Gastec (two that we use predominantly)
• Kitagawa.
• Komyo
• Rikagaku
• RAE
• Sensidyne

To select the appropriate gas detection tube you need to know what gas or gases is/are to be detected, and at what probable concentrations the gas may be present, or at what level of exposure the test is to be conducted.

NIOSH and other agencies publish specific test parameters that industrial hygienists use for industrial testing for the presence of gases in buildings or outdoors.

Check with the gas tube supplier: A building inspector, IAQ inspector, hygienist, building authority, or fire department who have the appropriate training and experience to perform these tests but who are uncertain about which detector tube to purchase should take advantage of the expert chemists and hygienists employed by the gas detector tube companies by calling for advice. Using a color-changing gas detector tube (colorimetric) is simple: the tube and the instruction sheet are removed from the package.

Read the gas sampling tube instructions: The gas sampling tube instruction sheet may give various numbers of pump strokes or test air volume to be sampled depending on the level of detection needed. (More pump strokes = more air = a more sensitive test.) The ends of the glass tube are broken off using a special cutter provided by the manufacturer of the tube.

Connect the gas sampling tube to the gas pump: The "outlet" end of the detector tube is inserted into the gas collecting pump. The "inlet" end of the tube is exposed to the air to be tested, and the pump is operated for the required number of strokes before looking for a color change on the tube's gas concentration scale. The documentation with each gas detection tube will describe the chemistry of the tube, its accuracy, its calibration, and the color change for which the user is to check.

Effects of temperature on gas level readings

The chemistry and thus the sensitivity and ultimate gas concentration reading shown by a colorimetric gas detection tube may be affected by temperature, it is important to read the temperature data in the gas detection tube specification sheet included with the particular gas detection tube being used. A Gastec gas sampling pump is available which includes a "thermal ring" which can provide this important data at the time that a measurement is obtained.

Effects of other chemicals and gases on gas level readings

The gas detection tube instructions may also list other gases which, if present, can affect the accuracy of the test. The gas sampling tubes shown here were used to test for the presence of perchlorethylene and show what the tubes look like before and after the sealed end is snapped off.

The chemistry and thus the sensitivity and ultimate gas concentration reading shown by a colorimetric gas detection tube may therefore be affected by other gases or chemicals present in the location being measured. For this reason it is also important to read the characteristics of the gas detector tube being used, and if there is risk of interference from other gases or chemicals it may be necessary to amend the test procedure, perhaps also including tests for the presence or level of these confounding gases. However while it may be a real problem in gas measurements in industrial environments, in residential settings we have rarely encountered this issue.

Other Tools Used to Measure Gases in Air

Guide to Using the TIF 8800 Combustible Gas Detector

The photograph shows our TIF 8800 combustible gas analyzer being used to sniff for possible sewer gases at an industrial sink. The TIF 8800 gas detection instrument is very sensitive to a wide range of combustibles and hydrocarbons, and is a quick and reliable way to check for gas leaks at LP or natural gas lines as well as for flue gas spillage. The user can adjust the sensitivity of the instrument using a knob visible at the lower right of the silver control panel in the photograph.

Because it responds to a wide spectrum of hydrocarbons and other gases or chemicals, it must be used with some intelligence.

When checking gas piping for leaks, if the plumber has recently sealed a connection using certain pipe sealants containing aromatic hydrocarbon solvents, this instrument will respond just as if there were a gas leak. It's a fabulous tool when used with thought, and it has often found gas leaks that were otherwise missed by the soap or match (dangerous) method used by many plumbers.

To maximize the sensitivity of the TIF8800 and thus its ability to detect combustible gas leaks, we recommend turning on the instrument while outside in fresh air (and away from any running automobiles or similar equipment). Let the instrument stabilize, adjust it for a steady but fairly sensitive beeping tone, then enter the area to be inspected.

Remember to test the air for combustible gases at various levels or heights: floor, mid-room height, and near the ceiling, since despite the varying weights of gases (such as LP gas and natural gas), a combustible gas or flue gas might be found at an unexpected location. For example, flue gases that should be heavier than air and should be found accumulating at floor level may in fact be accumulating at ceiling level in a building where they are carried while mixed with other hot or warm combustion air products (which rise by natural convection).

Using the TIF 5000 automatic halogen leak detector

The TIF 5000 automatic halogen leak detector is used for air conditioning and cooling system refrigerant leak detection. As you'll notice in our photograph of our instrument, its external appearance is similar to the TIF 8800 except that the 8800 detects a wide range of combustible gases while the TIF 5000 is designed to focus on the halogen gases - air conditioning refrigerants such as the now discontinued R12 and R22.

Instructions for use of the TIF5000 to check for refrigerant gas leaks couldn't be much simpler, and they are printed on a label affixed to the device:

1. Turn the TIF 5000 on.
   a. If the red LED does not light, replace the batteries in the detector.
   b. If the red LED lights but the instrument does not emit a tone, replace the sensing tip
2. Begin searching for leaks

But as with other devices of this type, if you're using it in an area which may already be contaminated with a high level of gas leakage, special (but simple) steps are needed to permit the leak detector to find the point of refrigerant gas leakage:

In an area heavily contaminated with refrigerant, (when a rapid, high pitched beeping signal [is heard]), turn [the] instrument off and then back on [while in the contaminated area] and resume testing for leaks.

This procedure is the opposite of what we do with the TIF8800 when testing for combustible gases (and the hazards are different since halogen gases do not present an explosion hazard).

What the instructions fail to point out is the practical procedure for actually examining air conditioning or refrigeration systems for refrigerant gas leaks.

• The refrigerant piping and cooling and condensing coils will need to be exposed for ready access.
• The leak detector is turned on and its proper operation confirmed.
• The detector tip is held close to the refrigerant piping and cooling coil surfaces, sequentially, starting at a convenient point and following all of the piping and tubing throughout its length.
• Look for stains on refrigerant piping or controls which may indicate a history of leaks (and refrigerant oil leakage too) at those locations.

The sensing tip on the TIF 5000 and some of the electronics of the instrument therefore are of course different.

Because debris contamination will interfere with proper operation of the TIF5000 halogen leak detector (refrigerant gas leak detector) the sensor is supplied with filter paper pre-cut into a cross shape which is inserted around the sensing tip under its protective spring cover. When the paper is soiled it is simply replaced.

The glass vial shown in our photo contains a substance used to confirm that the sensing tip will respond to a halogen gas (refrigerant gas) leak as it should.

Other specialized gas detection methods include use of solid state circuitry, CMS chips, and special instruments which may be designed to give a quick alarm or a reading in PPM for specific gases. Other gas and air monitoring equipment use pumps which collect and insert a specific volume of air into a vacuum container for later analysis. We've found that for typical field use, the colorimetric gas detector tube method is extremely convenient and very accurate, and it presents minimal requirements for instrument calibration.

To return to our air conditioning and refrigeration diagnosis articles go to AIR CONDITIONING SYSTEMS

Warnings about Relying on Instruments for Detection of Hazardous Gases in Buildings

OPINION-DF: In 1991, for ASHI, the American Society of Home Inspectors I authored or edited several articles on the use of instruments to test for evidence of dangerous flue gas leaks such as carbon monoxide in residential buildings. We were excited by the possibility of improving the level of safety afforded by a professional home inspection by permitting home inspectors to use instruments to perform simple screening tests for toxic or dangerous carbon monoxide gas leaks. Inspectors were already using the TIF 8800 described above, but that wide spectrum instrument could not focus specifically on, nor give numeric levels of carbon monoxide gas alone.

Quite a few home inspectors rushed to buy and some continue to use any of a variety of excellent and sensitive specialized pocket-sized gas detectors designed to screen specifically for carbon monoxide. Particularly in parts of the U.S. where home inspectors had found that the level of expertise offered by their local gas distribution companies was a bit weak, they were anxious to have a more reliable safety check tool for buildings heated by natural or LP gas.

In my view these articles encouraging the use of carbon monoxide detection instruments in the hands of some of these home inspectors was a disaster. Home inspectors who were not technically inclined, home inspectors who were more focused on the bottom line (profit), and inspectors who were looking for a way to simply speed up their inspection while doing less work, simply purchased one of these instruments, turned it on, and left it to check the heating system for CO leakage while they, being efficient and fast fellows, went off to inspect something else.

In other words, some home inspectors stopped inspecting the heating system as thoroughly as they had before relying instead on the instrument to do their work for them. Those inspectors, thinking that their job was done, simply reported that the instrument did or did not detect any carbon monoxide, and they disclaimed further responsibility for the condition of the heating equipment or even for the accuracy of the test they had performed. What was wrong with this approach?

• A complete visual inspection of the heating system, flue vent connector, chimney externals, controls, and safety devices is essential to form a reasonable opinion about the condition, usability, and safety of a heating system. Use of an instrument to check for the presence of a single gas is an inadequate substitute.
  
  
• The production of dangerous carbon monoxide varies enormously at a given heating system over a short time and for a variety of reasons. Testing with a door to the boiler room or furnace room open or shut can completely change the supply of combustion air (in some cases) and thus can "turn on" or "turn off" the production of dangerous carbon monoxide.
  
  
• Many other safety operating defects may be present and may be very important besides the test for carbon monoxide release.

In sum, there is a place for and good use for test instruments during building investigation, but they are not and should not ever be a substitute for a careful and thorough visual inspection and history-taking by an expert. Those "high speed" inspectors would have performed a better service for their clients by encouraging them to purchase and install smoke detectors and home-use carbon monoxide detectors than to hasten their inspection by using an unattended CO instrument in the home. Our article CARBON MONOXIDE - CO includes a photograph of a simple and effective carbon monoxide detector intended for homeowner installation and use.

Warning: About Selecting the Proper Gas Detection Tube

Gas Tube and Gas Pump Must be Compatible

Colorimeteric 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.

For example, as we were informed in May 2008 by Nextteq Gastec^TM detection tube distributor in the U.S., Gastec tubes that are currently available are not intended for use on the Sensidyne^TM 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.\

Gas Tube Must Be Properly Sensitive to the Gases Being Investigated

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.

Use links just below or at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.

CARBON MONOXIDE - CO
CARBON DIOXIDE - CO₂
OXYGEN - O₂
GAS MEASUREMENT TOOLS
  Use of a Drager pump
  How Colorimetric gas detection tubes work
  Using the TIF 8800 Gas Detector
  Using the TIF 5000 Gas Detector
  Warnings re instruments for detection of gases
  Warning: choose the right tube for gas detection

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