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ACCURACY vs PRECISION of MEASUREMENTS
AIR CLEANER PURIFIER TYPES
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AIR QUALITY IMPROVEMENT STRATEGIES
ANIMAL or URINE ODOR SOURCE DETECTION
BACKDRAFTING HEATING EQUIPMENT
BIBLIOGAPHY for ENVIRONMENTAL HEALTH, MOLD, IAQ
BIOGAS PRODUCTION & USE
BLOWER DOORS & AIR INFILTRATION
BOOKSTORE - ENVIRONMENTAL
BUILDING SAFETY HAZARDS GUIDE
CARPETING & INDOOR AIR QUALITY
CHINESE DRYWALL HAZARDS
CHLORINE IN DRINKING WATER
COMBUSTION PRODUCTS & IAQ
COMBUSTION GASES & PARTICLE HAZARDS
CONDENSATION or SWEATING PIPES, TANKS
CPSC Indoor Air Pollution Book Online Copy
DRAFT MEASUREMENT, CHIMNEYS & FLUES
DUST SAMPLING PROCEDURE
EMERGENCY RESPONSE, IAQ, GAS, MOLD
ENVIRO-SCARE - PUBLIC FEAR CYCLES
ENDOCRINE DISRUPTORS at BUILDINGS
Fireplaces & Woodstove Contaminants
FLAME COLOR, BLUE vs YELLOW COMBUSTION
Formaldehyde Gas Hazard Reduction
GAS DETECTION INSTRUMENTS
GAS LP & NATURAL GAS SAFETY HAZARDS
GAS LP & Natural Gas Pressures
HEATING OIL EXPOSURE HAZARDS, LIMITS
HOUSE DUST ANALYSIS
HOUSE DUST COMPONENTS
HUMIDITY CONTROL & TARGETS INDOORS
HYDROGEN SULFIDE GAS
Indoor Air Pollution Book Online CPSC
INDOOR AIR QUALITY & HOUSE TIGHTNESS
INDOOR AIR QUALITY IMPROVEMENT GUIDE
LP & Natural Gas Pressures
GAS LP & NATURAL GAS SAFETY HAZARDS
MOLD ODORS, MUSTY SMELLS
MSDS Material Safety Data Sheets
MVOCs & MOLDY MUSTY ODORS
Museum Artifact Preservation
ODORS GASES SMELLS, DIAGNOSIS & CURE
ODORS IN WATER
OXYGEN - O2
PARTICLE SIZES & IAQ
PESTICIDE EXPOSURE HAZARDS
PLASTIC ODORS-SCREENS, SIDING
PLUMBING SYSTEM ODORS
PVC - VINYL BUILDING PRODUCTS
RADON HAZARD TESTS & MITIGATION
METHANE GAS HAZARDS
SEPTIC SYSTEM ODORS
SMELL PATCH TEST to Track Down Odors
SULPHUR & SEWER GAS SMELL SOURCES
UFFI UREA FORMALDEHYDE FOAM INSULATION
URETHANE FOAM Deterioration, Outgassing
VAPOR CONDENSATION & BUILDING SHEATHING
VENTILATION in BUILDINGS
VINYL Siding or Window PLASTIC ODORS
VOCs VOLATILE ORGANIC COMPOUNDS
WATER ODORS, CAUSE CURE
Toxic or dangerous gas measurement 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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While 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, 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 (such as CARBON MONOXIDE - CO poisoning).
Toxic or Hazardous Gas Detection using Calibrated Pump and Gas Detection Tubes
The 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. 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.
Watch out: be sure to read GAS DETECTOR WARNINGS .
To convert between % and ppm see CONVERT PPM to % CONCENTRATION
Gas Tube and Gas Pump Must be Compatible
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.
Gas Tube Must Be Properly Sensitive to the Gases Being Investigated
Watch 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.
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Frequently Asked Questions (FAQs)
Question: what factors affect the accuracy of gas detection instruments & methods?
I am sending this mail on behalf of [an environmental testing company in] Thessaloniki, Greece. We have recently acquired a gas detector. I would like to ask you if you could send us any information regarding any possible factors that may affect and how, the accuracy of the measurement (indoor and outdoor) with the detector (environmental or technical). This would help us a lot with the proper understanding and use of the detector. - A.M. Thessaloniki Greece 9/14/2012
Thank you for the interesting or I should say absolutely critical question - it helps us realize where we need to work on making our text more clear or more complete. A competent onsite inspection by an expert usually finds additional clues that would permit a more accurate, complete, and authoritative answer to gas measurement - such as observing specific site conditions that would mess up your instrument results - more than we can give by email alone. You will find additional depth and detail in articles at our website.
That said I offer these comments:
First, here is a list of articles in which we discuss the use of gas testing instruments:
Particularly, take note of GAS DETECTOR WARNINGS
Certainly there are different classes of gas detection instrument problems and mistakes depending on variables such as
I found many years ago that there are problems with both false positives (detecting a "problem" level of a gas) and false negatives (missing an existing problem).
An example of false positives is using the TIF8800 - which will respond to your breath, or a flatulent bystander (no joke, I've encountered this).
After making a few conference presentations on CO detection devices we saw a surge in inspectors using them - it was horrible. What developed was the fellows stopped looking at the building, stopped thinking, and just plopped an instrument somewhere to take a reading - reporting the results and disclaiming any further responsibility.
I would start with a clear definition of the problem: what are we looking for, why, and thus where and how might a gas contaminant originate and where it might be found. I'd match the instrument, test, methodology to the problem.
I'd also check with the maufacturer and the instrument's specifications against the problem being studied. And I have had very good experience calling both the equipment manufacturers and, in the case of specific gas tests using colorimetric gas detection tubes or other specialized instruments, I've been grateful to the technical support staff at the manufacturers: people who've been willing to help assure that the proper test is selected for the problem at hand.
Watch out: making a mistake can be dangerous or fatal for building occupants. I think that it's for this reason that our local fire department, called to a home where there is a complaint of carbon monoxide detector alarm sounds, is reluctant to delcare a building "safe" just because their instrument detects nothing at the time of their visit. The experienced investigators know that many variables can cause the presence of a gas to wax and wane in detectability in and around a building.
Ultimately, in most cases of general field investigation for the detection of toxic or harmful gases, I would trust the results of gas detection instruments only if the instrument detects a problem; I would not fully trust a negative result.
Perhaps if you can tell me more of what you are up-to and what instrument you're talking about we could get more specific
Thank you very much for your email. This really helps us in the proper understanding of any factors that may occur during a measurement and can change its results. Moreover we will be properly prepared to face the problems mentioned. Our company Envia Environmental Solutions is specialized for some years, as you can see from our website (www.envia.gr)in the deodorization of industrial areas from malodorous gases.
For this purpose and recently acquired the Eagle 2 multi gas detector from RKI to help us better identify malodorous pollutants and subsequently deal with them with the use of our products. It can detect CO, O2, NH3, CH4, H2S and VOCs and we wanted to find out which environmental or technical factors can affect the accuracy of its measuring capability, because our company is new in this field. I will keep you informed about the instruments' performance. - A.M. Thessaloniki email@example.com
Thanks for the added information; you'll see at my website that I've had a long interests in and some experience in odor source tracking and remediation.
In my experience, detecting a specific gas MIGHT, SOMETIMES point to a correctable source, particularly in industrial applications where there is more likely to be a recognizable and specific gas or chemical source.
But very often we get an odor complaint whose nature is uncertain, whose chemistry is a complex of molecules not a single specific chemical or gas (excepting methane and sewer gas problems), and whose location is mysterious to the building occupants.
Or even after a known source and event there may remain odors lingering that have been absorbed by building materials but the occupants don't know which materials are harboring the odor.
An example is the over-dose of ozone during a misguided odor remediation attempt; some building materials become oxidized - but which are the prime offenders?
Performing an in-air gas test is not going to give much help in remediation guidance in such cases.
Instead, a thoughtful review of building history along with our smell patch test approach can point to the odor source and the odor remedy.
Our home base for this topic is at ODORS GASES SMELLS, DIAGNOSIS & CURE
In the Related Topics found near the top of that page you'll see the major topics on which I've provided information. including SMELL PATCH TEST to Track Down Odors
Questions & answers or comments about how to detect & measure hazardous gases in buildings.
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