ASHRAE Journal - November 2010 - 74

engineer’s notebook
was found to be really bad stuff 9 and was banned in consumer products in 1970. The major industrial use that continued was in the making of refrigerants such as R-11 and R-12. That use dwindled, of course, with the Montreal Protocol in 1989. So even though Logue, et al., found significant amounts of carbon tetrachloride in the indoor air, it was not put on the priority hazards list because there were no sources. The existing levels are presumably coming from the long residence time it has in the global atmosphere, as there are no longer domestic10 sources of any significance. Another interesting chlorine compound is chloroform. It is a precursor to carbon tetrachloride and is similar to it, but less hazardous. It can be a hazard in some homes, usually when the concentration in the water is elevated. generated, they may dominate the other listed hazards. Their health impacts are well studied. Since they come from specific activities/situations, they are usually either present or not. Radon is a radioactive, noble gas that is a problem in certain parts of the country where it can be a significant hazard. It typically is transported via soil gas into the building. In those areas, radon-resistant building practices can be used as can radon mitigation protocols. Radon is not usually a concern unless the soil has radium-bearing materials. Fine Particles are not technically chemicals, but are nevertheless a priority hazard. Their impacts on the body have to do less with their composition than their size. Large particles do not penetrate very far in the lung and can be removed relatively easily, and therefore do not cause much problem.11 Finer particles come from many different sources both inside and outside of buildings. As mentioned earlier, combustion is a prime source of particles, but there are other chemical and physical processes that can produce and transport them.12 Water Vapor is not actually a contaminant at all, but it can be problematic. If the concentration of water in air (i.e., the

other stuff
Other chemicals such as cadmium or chromium are important to health but not related to indoor air. The following chemicals are important to indoor air at least some of the time. Carbon Monoxide and Environmental Tobacco Smoke are special cases of burned stuff. When these contaminants are

9. For example, when heated in air carbon tetrachloride can make phosgene, which was the chemical weapon used in WWI when it was discovered that chlorine by itself was not as effective at killing people as hoped. 10. In fact, the sources of carbon tetrachloride you just breathed are likely foreign. The time for it to mix in the atmosphere (~1 year) is much less than its residence time (~50 years) and that makes a global issue. We are getting it from developing countries that have not banned its use. 11. That is unless you are allergic to what they consist of, which can be the case for pollen or pet dander. 12. If curious, read The Secret Life of Dust by Hanna Holmes (2003). You will be impressed.

ASHRAE Journal

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November 2010

ASHRAE Journal - November 2010

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