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A Toxic Gas Testing Sampling Plan for Residential Indoor Air Investigations InspectAPedia®  -     Indoor air quality testing for toxic gases - level of toxicity of gases How to test for toxic gases indoors and what levels of each gas are acceptable

This document outlines gas toxicity levels and gas testing procedures we use in field IAQ and environmental health investigations for a range of indoor gases which may be produced by building product outgassing, mold and mold related volatile organic compounds MVOCs which people report as a "moldy smell", mechanical systems such as heating system-produced carbon monoxide or flue gases, fire damage, or contamination from nearby industrial, beauty parlor, dry cleaning, or other activities which often produce noxious or toxic odors and gases. At Toxic Gas Exposure Effects we discuss the exposure effects for various toxic gases. At Volatile Organic Compounds VOCs we discuss several chemicals and gases found indoors and offer advice for reducing indoor exposure.

Readers of this document should also see HEAT EXCHANGER LEAKS. © Copyright 2009 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.

I.a. Indoor Residential Toxic Gas Test Selection - Some Suggested Tests

Depending on the building history and occupant complaints, and with advice from industry experts, for screening purposes I select one or more gas detection tubes [1] prepared by Sensidyne™ or Drager™ or one or more multiple simultaneous gas detection sets which have been prepared by Draeger Safety specifically for fire scenes. [2]

Gas detector tubes, used with a special calibrated Sensidyn™ or Drager™ pump [3] provide specific, accurate tests for the presence of target substances at the moment of testing. A list of gas tests and test sets which I have frequently used in field investigations is listed below. 

Other tests for specific substances: over 200 tests for over 500 different gases are available by using specific detector tubes. I can provide these when there is risk of a specific substance in a building. Unless there is a reason given for a narrow specific gas test in a building such tests are not economical and are simply "shooting in the dark."

We also select among several methods for particle collection from appropriate complaint and non-complaint areas,  including air sampling, surface tape lifts, surface, carpet, or furniture vacuum.

Where bacteriological risks are considered, such as where there has been a history of sewage leaks, the inspector/test consultant may include floor surface sterile swabs from the complaint area and control non-complaint areas. Sample specifics and test results along with related remediation advice are detailed in our Field Investigation and Lab Test Report.

Odor Source Identification & Evaluation

Odor source detection procedures are also available at this website but they are not discussed in this article. Odor detection and removal are described in detail in our separate odor diagnosis document at How to Find & Remove Odors, Gases & smells in Buildings

I.b. Indoor Air Investigation Tests for substances in gas form

Draeger Simultaneous Test Sets I, II, and III:

Building contents and the presence of hazardous substances are unknown at the start of fighting a fire. Studies have shown more than 450 substances are produced by a fire and possibly in other circumstances. Not all of these potentially toxic gases are present at every fire, but 11 inorganic gases are preset at most fires.

Ten of these gases and substances produced by burning common materials found in buildings are addressed by the Draeger Simultaneous Test Sets I and II. [5]

Set III screens for organic gases. The Draeger Simultaneous Test Sets screen for these specific substances in the immediate vicinity. These sets also record a broader spectrum of substances, and the reaction systems used are deliberately non-specific in order to screen for likely and most-dangerous substances. The individual sampling tubes are marked to indicate the presence of the test substances at 1x and 5x the threshold limit value (TLV) [for maximum short term exposure in industry; there is not a similar residential standard].

a.   Drager Simultaneous Test Set I

i. Acid gases

ii. Hydrocyanic acid

iii. Carbon monoxide

iv. Alkaline gases

v. Nitrous fumes

b. Drager Simultaneous Test Set II

i. Sulphur dioxide

ii. Chlorine

iii. Hydrogen sulphide

iv. Carbon dioxide

v. Phosgene

c.   Drager Simultaneous Test Set III

i. Keytones

ii. Aromatic hydrocarbons. Calibrated for toluene; benzene and xylene are indicated with similar sensitivity. The TLV⁴ for benzene is much lower than xylene but the acute risk involved in the two substances is alike. They share the same IDLH (2000 ppm).

iii. Alcohols. Such as methanol.

iv. Aliphatic hydrocarbons. E.g. n-hexane (extremely low TLV(TWA)=50ppm); the TLV for most of the other aliphates is assessed to 300 ppm. The acute risk involved in hexane, heptane, and octane is almost identical; all substances are assessed to similar IDLH values.

v. Chlorinated hydrocarbons. Imprinted tube values pertain to perchloroethylene. A general prediction can be made with respect to the sensitivity of other compounds with certain reservations. (Gasoline vapors will shorten the reading as long as their concentration is more than 100 ppm).

Benzene Gas Characteristics, Toxicity, Simple Gas Exposure Measurements

Benzene [7] 0.5/a tests in the indoor environment

If there is a particular concern for Benzene we perform a test for this substance. We select a sampling tube which is not Benzene specific in order to also screen for other aromatic hydrocarbons including toluene, xylene (more likely to be in carpet out gassing than benzene) and ethel benzene. Sensitivity 0.4 to 10 ppm (40 to 2 strokes). +/30%.  

More information about gas hazards, gas toxicity, or other environmental hazards is available from public and professional agencies and associations such as the American Industrial Hygiene Association (AIHA) www.aiha.org, OSHA www.osha.gov, and the Mine Safety & Health Administration www.msha.gov. Also see Industrial Hygiene News.

Carbon Dioxide Gas Toxicity, Simple Gas Exposure Measurements

Carbon dioxide 100/a

We have this test available for field use as a general indicator of the level of fresh air and air exchange in a building, but not if the building is unoccupied or aggressively ventilated at the time of the inspection. If used, we perform this test using the Gastec pump and tubes produced by Sensidyne. We do not perform this test separately if we are using the Draeger Simultaneous Test set as it is already included in that set. Sensitivity 100 " 3000 ppm. 0.01 " 0.3 Vol.-%.

Details about carbon dioxide gas toxicity or CO2 exposure hazards are provided in a separate article at Toxicity of Carbon Dioxide Gas Exposure, CO2 Poisoning Symptoms, Carbon Dioxide Exposure Limits, and Links to Toxic Gas Testing Procedures

Carbon Monoxide Gas Toxicity, Simple Gas Exposure Measurements

Carbon monoxide 2/a:

We may use this test as a safety screen in buildings where there is other evidence of a questionable gas-fired heater. If used, we perform this test using the Gastec pump and tubes produced by Sensidyne. We do not perform this test separately if we are using the Draeger Simultaneous Test set as it is already included in that set. Sensitivity 2-60 ppm. Alternate: Sensidyne™ Gastec™ 1/La 8-1000 ppm or 25-500 ppm.

Readers should also review our more detailed review of CO hazards at Toxicity of Carbon Monoxide Gas Exposure, Carbon Monoxide CO Poisoning Symptoms, Carbon Monoxide Exposure Limits, and Links to Toxic Gas Testing Procedures

More information about gas hazards, gas toxicity, or other environmental hazards is available from public and professional agencies and associations such as the American Industrial Hygiene Association (AIHA) www.aiha.org, OSHA www.osha.gov, and the Mine Safety & Health Administration www.msha.gov. Also see Industrial Hygiene News.

Formaldehyde Gas Characteristics, Toxicity, Simple Gas Exposure Measurements

Formaldehyde 0.2/a:

Because this gas is produced at virtually all house fires and because it is a well-known respiratory and eye irritant produced by many building materials even without combustion effects, if there are owner/occupant complaints, this test may be performed using the Gastec pump and tubes produced by Sensidyne or by the Draeger accuro pump and their tubes. Sensitivity 0.2 to 2.5 / 0.5 to 5 ppm at 10 / 20 strokes.  Alternative: Sensidyne ™ Gastec™ 91/L 0.1-40.0 ppm

Formic acid Gas Characteristics, Toxicity, Simple Gas Exposure Measurements

Formic acid1/a:

Because this gas screen addresses acid gases which can be expected to be produced by fire, heat, or oxidation (such as from ozone treatment) in commercial and residential properties it is an important screen for this topic. Sensitivity 1 to 15 ppm, 20 strokes.

More information about gas hazards, gas toxicity, or other environmental hazards is available from public and professional agencies and associations such as the American Industrial Hygiene Association (AIHA) www.aiha.org, OSHA www.osha.gov, and the Mine Safety & Health Administration www.msha.gov. Also see Industrial Hygiene News.

Ozone Gas Characteristics, Toxicity, Simple Gas Exposure Measurements

Ozone:

At high or low levels (various test sensitivities are available) produced by popular indoor air "purifiers" and by commercial treatments for odors is a highly-reactive oxidizing gas which is dangerous to lung tissue itself. This gas may react with other building materials (as an oxidant) to produce secondary outgassing products which are also irritants or potentially unsafe. Ozone is highly reactive and volatile and may not be present in a building long after it was applied. Choice of use or omit this screen depends on the circumstances of the particular investigation. As a regular practice I include this screen where ozone generating equipment is in use or where commercial equipment has been very recently in use. Sensidyne™ #182SB 2.5-100 ppm / #182U 0.025 " 3.0 ppm.™

See Ozone Warnings at http://InspectAPedia.com/sickhouse/OzoneWarnings.htm

Details about Ozone Gas hazards and the use of ozone generators or using ozone as a mold remedy are provided in depth at the following articles:

• The Use of Ozone Generators Indoors for Control of Odors and Mold Removal in Buildings: A Summary of Hazards and False Claims
• The Hazards of Ozone & Ozone Gas Generators Ozone Gas Exposure Hazards - A Summary of Ozone Hazards Indoors
• How, When, and Why to Test for Ozone in Buildings
• Ozone Toxicity & Ozone Gas Exposure Hazards

Toluene Gas Characteristics, Toxicity, Simple Gas Exposure Measurements

Toluene 5/b:

Because this is one of the most sensitive gas screens available to address gases which can be expected to be produced by fire, heat, or oxidation (such as from ozone treatment) in commercial and residential properties it is an important screen for this application.

Toluol is a common contaminant produced by oxidized or burning carpets. Sensitivity 5-300 ppm.

II.c. Associated Particulate Testing

These tests are not normally part of indoor gas testing but may be added on request or based on site conditions.

Non-regulated particulates,

Non-regulated particles such as soot from fires, can include ultra-fine particles which can be breathed deeply into the gas-exchange area of the lung. We use both settled surface dust collection (adhesive tape) and surface or crevice-dust collection (particle collection by vacuum using Zefon-type "Air-o-cel(R)" or MCE-filter cassettes to obtain material for microscopic examination.

Quantitative testing using other methods that permit calculating of particle exposure by weight are available but we do not employ them [it is outside our area of expertise]. If such particles were collected and examined they are shown in the Lab Report.

Tests for Common indoor allergens & particles such as mold, pollen, cat or dog dander, fiberglass insulation fragments

Allergens and respiratory irritant particles such as animal dander, insect fragments, mite fecals, pollen, and mold spores may be sampled by a variety of means: slit-impaction air samplers, vacuum samples, surface tape, bulk, swab, and culture.

The specifics of what particle collection methods used, how and where particles were collected, the relationship of the collection areas to building occupants, complaints, or other important risk factors, and the building conditions that can dramatically affect the apparent particle level (such as turning on or off a fan during air sampling) should appear in the field investigation report and Lab Report.

See Validity of Common Indoor Mold Sampling Techniques and MOLD DETECTION & INSPECTION for examples of particle collection procedures.

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Toxic Gas Test Procedures
Toxic Gas Test Selection
Indoor Air Tests
Particulate Testing
  Non-regulated particulates
  Common indoor allergens
Gas Testing Limitations (article in proc)
Gas Toxicity Levels
  Gas Exposure Limits
  Volatile Organic Compounds
  Gas Toxicity Footnotes

• Thanks to Alan Carson and Bob Dunlop, Carson Dunlop, Associates, Toronto, for permission to use illustrations from their publication, The Illustrated Home which illustrates construction details and building components. Carson Dunlop provides home inspection education, publications, report writing materials, and home inspection services. Alan Carson is a past president of ASHI, the American Society of Home Inspectors.
• Daniel Friedman - principal author/editor of the InspectAPedia^® Website. Daniel Friedman is a consulting professional member of the American Industrial Hygiene Association  - AIHA. His credentials and experience can be viewed at InspectAPedia.com/danbio.htm
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Gas Exposure Standards (workplace-based)

The purpose of onsite gas inspection and testing is to perform a general screen for the presence of specific problematic substances in response to specific concerns raised regarding the target property. Individual complaints about indoor air quality can occur at extremely-low levels of certain gases or particles, in fact at levels considerably below typical allowable industrial permitted exposure levels (PEL's). Therefore we may select tests which screen for levels of gases considerably below permitted limits for industrial workplace exposure.

Gas Tests: test equipment is checked for proper operation and calibration before and after the investigation; gas detection tests are conducted under operating conditions meeting the manufacturer's requirements; these tests are applicable only to the place, time, and date of measurement; the tests are not technically exhaustive. Several instruments are used, depending on whether we are screening for presence/absence of combustible gases, checking general indoor air quality, or testing and making quantitative measurements of specific gases in an environment. Some instruments are particularly helpful in tracking odors or leaks to their source.

Draeger Sampling Pump: we use the Draeger accuro ™ Pump and Draeger-Tubes for gaseous substance sampling for both detecting the presence/absence of specific gases and for quantitative measurements of gas levels.

The Sensidyne Gastec piston pump and Gastec™ tubes for test for presence/absence of and level of certain gaseous substances.

Both of these toxic gas testing pumps are factory calibrated at 100 cc, and are leak-tested before and after each investigation. The adsorption tubes used for substance screening/identification are factory-calibrated. Other tests for specific substances: over 200 tests for over 500 different gases are available by using specific detector tubes. I can provide these when there is risk of a specific substance in a building. Unless there is a reason given for a narrow specific gas test in a building such tests are not economical and are simply "shooting in the dark."

The TIF 8850 combustible gas detector is a broad-spectrum gas screening instrument which is also useful to track and pinpoint the source of odors or leaks. A partial list of gases detected by the TIF 8850 and its detection limits includes: Acetone 50ppm, Acetylene 50ppm, Alcohols, Ammonia (R717) 20ppm, Benzene, Iso-Butane (R600a) 500ppm, Chlorine 1ppm, Ethane (R170) 500ppm, Ethylene 500ppm, Gasoline 1ppm, Hydrogen 500ppm, Hydrogen Sulfide 5ppm, Lacquer Thinners, Methane (Natural Gas) 500ppm, Methyl Chloride 5ppm, Methanol 50ppm, Methyl Ether 500ppm, N-Butane, Naphtha, Propane ("bottled gas" R290) 500ppm, Toluene, Vinyl chloride 5ppm. MDL are generally 1-500 ppm. The device uses a TIF 8801 sensing tip.

Toxic Gas Exposure Hazards and Test Protocols including links to our toxic gas exposure screening and gas testing protocols.

Gases: Toxic gases, indoor exposure levels, testing, identification

• A Toxic Gas Testing Plan: A Gas Sampling Plan for Residential and Commercial Buildings lists some of the toxic indoor gases for which we test, depending on the building complaint and building conditions
• Gas Exposure Hazard Levels: for Toxic Gas Exposure to Ammonia, Arsine, Arsenic, Bromine, Carbon Dioxide, Carbon Monoxide, Hydride, Ozone - allowable exposure levels and hazard levels
• Carbon Dioxide Gas Toxicity hazard levels & testing
• Carbon Monoxide Gas Toxicity hazard levels & testing
• Formaldehyde: US EPA. UFFI (Urea Formaldehyde Foam Insulation) was previously considered a hazard (formaldehyde outgassing). Subsequent research virtually closed concern regarding this material; however formaldehyde appears to remain a health concern for sensitive individuals.
• Ozone Warnings - Use of Ozone as a "mold" remedy is ineffective and may be dangerous.
• Sampling for gases in air such as VOC's, MVOC's, toxic chemicals, and combustion products.
  Unfortunately no single test or tool can detect all possible building contaminants. We use methods and equipment which can test for common contaminants. If the identity of a specific contaminant is known in advance we can also test for a very large number of specific contaminant gases in buildings. We use gas sampling equipment provided by the two most reliable companies in the world, Draeger-Safety's detector-tubes and Drager accuro™ bellows pump, the Gastec™ cylinder pump and detector-tube system produced by Gastec or Sensidyne, and we also use Sensidyne's Gilian air pump. For broad screening for combustibles and a number of other toxic gases and for leak tracing we also use Amprobe's Tif8850. All of these instruments, their applications, and sensitivities (minimum detectable limits) for specific gases are described in our Gas Sampling Plan online document.
• Radon Gas U.S. EPA Radon level maps

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