Table 1.

Types of problems found in 203 indoor air quality investigations carried out by National Institute for Occupational Safety and Hygiene

Problem	No.	%	Notes
Contamination (inside)	36	18	Exposure to chemical or other toxic agents generated within the office space, e.g., methyl alcohol from a spirit duplicator, methacrylate from a copier, sulfur dioxide from a heating system, amines used in a humidification system, chlordane used as a pesticide
Contamination (outside)	21	10	Exposure to a chemical or other toxic substance originating from a source outside the building, e.g., motor vehicle exhaust fumes, construction activity, underground petrol spillage
Contamination (building fabric)	7	3	Problems from the material used to construct the building (figure excludes asbestos), e.g., formaldehyde, fiberglass
Inadequate ventilation	98	48	Symptoms may be due to low levels of multiple contaminants and/or poor ventilation
Hypersensitivity pneumonitis	6	3	Problems due to a reaction to microorganisms in the building environment
Cigarette smoking	4	2
Humidity	0.9	4
Noise/illumination	2	1
Scabies	1	0.5
Unknown	19	9

Source: Melius 1984