Photograph of a Drager hand pump used to measure carbon dioxide levels in the environment. Warnings for Users of Toxic Gas Measurement Instruments
     

  • GAS DETECTOR WARNINGS - CONTENTS: Warnings about using instruments for detection of toxic gases - ecommendations for gas measurement instruments, gas detector tubes, Draeger & Gastec, Komyo Rikagaku Kitagawa, RAE, & Sensidyne gas detection tubes & pumps for detection of gases. Dangers of choosing the wrong gas detector tube. Gas Detector Tube Chemical Hazards.
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Safe use of gas leak detector tools: this document outlines warnings for people using gas detection tools and sensors 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.

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

Photo of a TIF 8800 combustible gas analyzer being used to check a kitchen sink drain for sewer gas leaksOPINION-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.

Shown at left, the TIF 8800 combustible gas analyzer, a very sensitive instrument.

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.

High Speed Home Inspecting?

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 of relying on gas detection tools:

Flue gas leak problem photo

  • 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.

    For example, 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.
  • Because the TIF 8800 responds to a very wide range of combustible gases, it is useful in tracking down sewer gas or septic gas odors as well. See

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

Colorimetric 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 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.\

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 gas detector 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.

How Birdwatching Can Inform Building Environmental Investigations

Bird nesting on house downspout (C) Daniel Friedman

Gas Detection Measurement Must be Made in the Proper Test Locations

At TIF 8800 Test procedure we explain and illustrate in detail that when testing for gases produced by combustion in a heating or hot water appliance, because combustion gases produced by the burner are quite hot, test points must extend beyond the appliance itself to look for accumulated gases near the room ceiling.

And at TIF 8800 FIELD TESTas well as

at TIF 8800 GAS DETECTOR we explain that when screening for heavier-than-air gases (including LP gas) tests need to be made close to floor level as well.

When birdwatching, if you look where the bird's aren't you won't find them. If you look where they are, you will.

The same thinking applies to screening buildings for hazards.

 

 

Gas Detection Measurements Must be Made at the Proper Times

Evidence of birds in the attic of a building even when the birds are not home (C) Daniel FriedmanAt CO DETECTION OPTIONS we explain that when using any gas detector tool to test inside of the air plenum for flue gas leakage, one critical test time is before the blower fan has come on.

Once the fan begins not only is building air in the plenum diluted, the pressurization of air around the heat exchanger is likely to change the direction of a combustion gas leak.

Our photo illustrates a second point, that there may be evidence of a problem (in this case bird guano or droppings in the building attic) even if the problem source is not visible or not present at the time of inspection. The birds are not home right now, but they've been having a nice time living in the attic of this home.

When birdwatching, if you look in the North for birds when they've migrated South for the winter you won't find them. Similar thinking applies when screening buildings for environmental or other hazards whose presence varies by time of day, weather, usage, or other varying site conditions.

Gas Detector Tube Chemical Hazards: Air Current Tubes & Smoke Generating Tubes: Safety Warnings

Watch out: the Dräger air current tube or "smoke tube" # CH16631 produces a sulfuric acid gas sulfuric acid H2SO4 /SO3 that is dangerous to life and is highly corrosive. Take a look at our copy of the Dräger MSDS for their CH25301 Air Current Tubes.

We stored this MSDS in the box with the rubber bulb and tube cutter provided by Dräger. These air current monitoring tubes are provided with rubber caps so that the tube can be "stopped" or shut down when not in use.

But the sulfuric acid was so corrosive that it not only caused the rubber caps to disintegrate, it actually "burned" or oxidized our copy of the MSDS paper form!

 

Continue reading at TIF 8800 GAS DETECTOR or select a topic from the More Reading links shown below.

Or see Drager GAS DETECTORS

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GAS DETECTOR WARNINGS at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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