Of course, virtually all of these are present to some degree in every building. They cause serious IAQ problems only when concentrations become excessive. Dusty surfaces, stagnant water and damp materials provide an environment ripe for microbial growth. When mold spores and other microbial particles become airborne, some building occupants may experience allergic reactions. One potential, but extremely rare, infection is caused by Legionella bacteria.
Cigarette smoke contains carbon monoxide, formaldehyde and thousands of other chemicals.
It presents a serious health risk to those exposed. Recent studies have shown that exposure to secondhand tobacco smoke may result in inner ear infections, asthma and lung cancer in nonsmokers. The EPA has listed tobacco smoke as a confirmed cancer-causing agent. Contaminants may also originate outside the building and enter via the outdoor air intakes or, when more air is removed by the HVAC system from the building than is supplied, by flowing into the building through any available gap. Poor IAQ occurs when ventilation is inadequate in keeping contaminant concentrations at levels that do not produce occupant health problems.