Programs that conduct tests which evaluate air and dust samples for evidence of pollutants such as carbon monoxide and other gases released from combustion sources such as oil, gas kerosene, coal, wood and tobacco products; household products such as air fresheners and cleaning solvents; emissions from malfunctioning stoves, furnaces or space heaters; chemical contaminants from workplace activities such as copying or printing; toxins produced by building materials and furnishings; output from central heating and cooling systems and humidifiers; biological contaminants such as animal dander, insect parts from cockroaches and dust mites, molds and mildew, bacteria, viruses and pollen; and outdoor sources such as radon, pesticides, pollen, fungal spores and outdoor air pollution. Testing may be requested in response to suspected cases of "sick building syndrome" in which occupants are becoming ill or on a preventive basis.