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How, When, and Why to Test for Ozone in Buildings
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• How and why to test for ozone levels in indoor air or at air purifiers used indoors
• The effects of using ozone in buildings to "purify air" or to "kill mold"
• The hazards of ozone generators in buildings

This article discusses ozone testing in indoor air. Ozone is widely promoted by ozone generating equipment companies and cleaning services for use in indoor building environments to deodorize, disinfect, "kill" mold, and for "general health". Ozone generators are also promoted for use to reduce the level of airborne particles, pollen, animal dander, and allergens, ostensibly to improve indoor air quality for asthmatics and people with allergies.

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TESTING FOR OZONE Contamination, Ozone Damage and Testing for Related Ozone-Related Outgassing Hazards

"Ozone is a highly toxic gas but even highly toxic substances can be encountered safely. The main concern with this material is that concentrations to which people are exposed do not average more than 0.1 ppm over an 8-hr day, and do not exceed that value by more than a factor of 2 or 3 during the exposure." [1]

Because ozone is highly volatile and is not likely to remain present in a building unless an ozone generating device is operating, we do not normally include ozone testing in building IAQ screening measurements for gases.

In exceptional circumstances we may test an indoor environment for ozone levels. Normally I do not, as this gas is so volatile and reactive that it would not be expected to remain in an environment.

However, the byproducts of using ozone gas at high concentrations and durations indoors (for example during a "mold remediation using ozone" may oxidize and cause outgassing from other building products. When circumstances warrant, I would screen for a variety of common outgassing products such as formaldehyde, benzene, formic acid and other acid gases, toluene and related gases. Our tests for these gases are described in our clients' sampling plan. I also may apply one or more of the three sets of multiple-gas hazard screen systems provided by Drager for the fire investigator profession.

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.

Ozone 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 for ozone where such equipment is in use (to detect dangerous current levels) or where commercial equipment has been very recently in use. Sensidyne™ #182SB 2.5-100 ppm / #182U 0.025 - 3.0 ppm.

Benzene 0.5/a: If there is a particular concern for Benzene I perform a test for this substance. I 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. Our test sensitivity is 0.4 to 10 ppm (40 to 2 strokes). +/30%.

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 1/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. Our test sensitivity 1 to 15 ppm, 20 strokes.

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. Our test sensitivity 5-300 ppm

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OZONE as a "CURE" for TOXIC INDOOR MOLD
WHAT IS OZONE- O₃
OZONE AIR PURIFIER WARNINGS
OZONE HAZARDS
STANDARDS FOR OZONE EXPOSURE
TESTING FOR OZONE
OZONE TOXICITY
OZONE ODORS, MOLD, REFS
OZONE as a "CURE" for TOXIC INDOOR MOLD

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