A large phagocytic cell found in the lung tissues that helps defend the body against viruses, bacteria, and other foreign intruders, generally by engulfing them.

Air which enters the house, either intended or not, to replace the air removed through exhaust and dilution.

Air brought into a building from the outdoors through the ventilation system, which has not been previously circulated through the system.

Operation of an IAQ program-including personnel and budgeting decisions, monitoring and feedback, legislative initiatives, internal information flows, and enforcement of State requirements.

Multiple Chemical Sensitivity. A term used by some people to refer to a condition in which a person is considered to be sensitive to a number of chemicals at very low concentrations. There are a number of views about the existence, potential causes, and possible remedial actions regarding this phenomenon.

2nd division of the C.N.S.

In toxicology, refers to the biochemical changes that a chemical undergoes in the body.

Milligrams per liter (parts per million). For practical purposes mg/L is assumed to be equal to ppm.

Microscopic forms of life.

Infection or pollution by microscopic organisms.