Harmful chemical compounds in the form of solids, liquids, gases, mists, dusts, fumes, and vapors exert toxic effects by inhalation (breathing), absorption (through direct contact with the skin), or ingestion (eating or drinking). Airborne chemical hazards exist as concentrations of mists, vapors, gases, fumes, or solids. Some are toxic through inhalation and some of them irritate the skin on contact; some can be toxic by absorption through the skin or through ingestion, and some are corrosive to living tissue.

Additionally, inhalation of non-toxic air contaminants like particulate dusts or microscopic fibers can result in damage to the lungs. Continued exposures to air contaminants can be just as harmful as exposure to toxic chemicals.

Nearly every industrialized nation has laws that specify the occupational exposure limits (OELs) for chemical compounds and air contaminants in the workplace. Additionally, several other non-governmental organizations also publish OELs based on independent research of toxicological and exposure data that are stricter than the governmental limits. OELs are specific to each individual chemical compound. These limits should be carefully followed for every regulated substance in order to ensure the health and safety of workers, and to avoid legal and civil action for non-compliance.

Chemical and air contaminant exposure can be controlled first by limiting the exposure time to hazardous materials. Additionally, workers should be supplied with proper personal protective equipment such as gloves, safety glasses, respirators, ventilation systems, aprons or coats, etc., to reduce or eliminate direct contact with hazardous substances.

Monitoring programs are also vitally important in preventing over-exposure to hazardous materials. Proper monitoring can determine if over-exposures exist and are also essential in litigation to prove safe working environments.