Energy Conservations Measures and Green Renovations & Construction

Indoor air purifiers that produce even small quantities of ozone may actually make the air dirtier when used at the same time as household cleaning products, scientists at U.C. Irvine have discovered.

Ozone emitted by purifiers reacts in the air with unsaturated volatile organic compounds such as limonene - a chemical added to cleaning supplies that gives them a lemon fragrance - to create additional microscopic particles, scientists found. Certain ionic purifiers emit ozone as a byproduct of ionization used for charging airborne particles and electrostatically attracting them to metal electrodes. Ozonolysis purifiers emit ozone at higher levels on purpose with the  ostensible goal of oxidizing volatile organic compounds in the air.

This research appeared online in Environmental Science and Technology.
"The public needs to be aware that every air purification approach has its limitation, and ionization air purifiers are no exception," said Sergey Nizkorodov, assistant professor of chemistry at UCI and co-author of the study. "These air purifiers can not only elevate the level of ozone, a formidable air pollutant in itself, but also increase the amount of harmful particulate matter in indoor air."

High levels of airborne particles can aggravate asthma and cardiovascular problems, and have been linked to higher death and lung cancer rates. Excess ozone can damage the lungs, causing chest pain, coughing, shortness of breath and throat irritation.

Nizkorodov and students Ahmad Alshawa and Ashley Russell conducted their experiment in a sparsely furnished office with a floor area of about 11 square meters. They placed an ozone-emitting air purifier in the middle of the room along with a large fan to better mix the air. At timed intervals, limonene vapor was injected in the room. Samples of the air were taken about one meter from the purifier and analyzed for ozone and particulate matter levels.

The researchers tested two types of air purifiers - a commercial ionic purifier that emits about 2 milligrams of ozone per hour, and an ozonolysis purifier that emits approximately 100 milligrams of ozone per hour.

Continuous operation of the ionic purifier without limonene resulted in a slight reduction in the average particle concentration, while operation of the ozonolysis purifier resulted in no detectable effect on the particle level. When limonene was added to the room, the particle concentration shot up in both cases, on some occasions up to 100 times the original level. Adding limonene to the room when a purifier was not operating produced little change in the overall particle level.

The scientists also developed a mathematical model that precisely matched their experimental observations. This model can be used to predict whether a given air purifier will make the air dirtier in a given indoor environment.

Scientific data on indoor air purifiers will be important as officials begin the process of regulating air purifiers that emit ozone. In September 2006, California Gov. Arnold Schwarzenegger signed into law Assembly Bill 2276, requiring the California Air Resources Board to develop regulations that will set emission standards and procedures for certifying and labeling the devices.

"State regulators should set a strict limit on the amount of ozone produced by air purifiers to protect the public from exposure to unhealthy ozone and particulate matter levels," Nizkorodov said.

Source: University of California - Irvine

Not all air-cleaning devices are appropriate for home use - some can be harmful to human health. The ARB recommends that ozone generators, air cleaners that intentionally produce ozone, not be used in the home. Ozone is a gas that can cause health problems, including respiratory tract irritation and breathing difficulty (Ozone and Health).

In response to legislation, Assembly Bill 2276 (2006, Pavley), the ARB has adopted a regulation to limit the ozone emissions from indoor air cleaning devices. For more information on the regulation, please visit: http://www.arb.ca.gov/research/indoor/aircleaners/aircleaners.htm

California Environmental Protection Agency - Air Resources Board

"A study by Harvard researchers says there is a more definite link than previously thought between mold in the home and the risk of severe asthma.

The study, which was published in the American Journal of Respiratory and Critical Care Medicine, concluded that individuals with certain genes were more likely to suffer serious asthma attacks in homes with high amounts of mold.

The researchers studied data from the Childhood Asthma Management Program, looking at children ages 5 to 12 with moderate to persistent asthma. They found 395 children and their parents who had certain expressions of chitinases, which are enzymes that break down the cell wall of fungus, known as chitin.
The scientists then classified the home environments of the subjects based on whether they had more or less than 25,000 mold colonies per gram of household dust. They found that 24% of their subjects lived in high-mold residences.

In homes with high amounts of mold, the researchers found "severe exacerbation of asthma that often included emergency room visits and hospitalization and appeared to be directly linked to the genetic expression of the chitinases enzymes."

The Environmental Protection Agency (EPA) has long listed mold as one of the key asthma triggers in the indoor environment, along with secondhand smoke, dust mites, and cockroaches and other pests.

The Harvard study, however, seems to show a more precise link than had been previously found."...

Indoor Environment Connections. Volume 11, issue 10. August 2010 by Tom Scarlett