A small, usually aquatic, plant which requires light to grow, often found on exposed areas of cooling towers.

A disease caused by species of legionella, an upper respiratory illness less severe than Legionnaires’ disease.

A suspension in a gaseous medium of solid particles, liquid particles or solid and liquid particles having negligible falling velocity.

A form of air treatment whereby temperature humidity and air cleanliness are all controlled within limits determined by the requirements of the air-conditioned enclosure.

Substances in the blood which destroy or neutralise various toxins or components of bacteria known generally as antigens. The antibodies are formed as a result of the introduction into the body of the antigen to which they are antagonistic as in all infectious diseases.

(Singular bacterium) a microscopic, unicellular (or more rarely multicellular) organism.

(Singular bacterium) a microscopic, unicellular (or more rarely multicellular) organism.

A substance which kills micro-organisms.

A community of bacteria and other micro-organisms, embedded in a protective layer with entrained debris, attached to a surface.

Water discharged from the system to control the concentration of salts or other impurities in the circulating water; usually expressed as a percentage of recirculating water flow.