An irritant response to a substance often occurs when the concentration exceeds some threshold value. Examples of irritant effects include eye irritation, odor, and nasal irritation. The concentration required to produce an irritant effect may depend on individual susceptibility. The duration of the irritant exposure is often important. RISK provides information on the time spent above a user specified irritant threshold concentration.
The avoidance of irritant risk is a major consideration in indoor air quality. For example, the ASHRAE ventilation rate standard 62-89 is designed to ensure that no more than 20% of the occupants of the building express displeasure with the indoor air quality. A major consideration in developing the standard was to provide sufficient outdoor air to avoid complaints due to human body odor.
Mølhave (1986) discusses irritation in indoor air and presents limited information on the concentrations of VOCs that might cause irritation. Wolkoff and Nielsen (1996) discuss a labeling system designed to minimize irritant risk from indoor materials. Seifert (1992) also provides a system for evaluating sources that includes irritant risk as a factor.
There is considerable research to develop source test methods to provide information on irritant risk due to pollutant emissions from indoor sources. Much of this research is based on using bioresponse testing to either replace or augment chemical testing. Muller and Black (1995) discuss one method of testing products to provide data necessary to estimate irritant risk.