ACID, ACUTE, ACUTE TOXICITY, AEROSOL, AFFF, AQUEOUS FILM-FORMING FOAM , ALCOHOL-RESISTANT FOAM, ASPHYXIA

ACID
A chemical compound whose aqueous solution turns blue litmus paper red, reacts with and
dissolves certain metals to form salts, and reacts with bases to produce salts and water. They are
capable of transferring a hydrogen ion (proton) in solution.

ACUTE
Describes a severe and often dangerous condition in which relatively rapid changes occur.

ACUTE TOXICITY
Adverse health effects occurring within a short time period of exposure to a single dose of a chemical or as a result of multiple exposures over a short time period, e.g. 24 hours.

AEROSOL
A colloidal suspension of liquid or solid particles dispersed in gas.

AFFF, AQUEOUS FILM-FORMING FOAM
Fire-fighting foam which flows on burning liquid as a film, providing rapid knock-down.

ALCOHOL-RESISTANT FOAM
Foam for use against fires involving liquids miscible with water, e.g. alcohol, acetone.

ANION
A negatively charged atom or group of atoms, or a radical which moves to the positive pole
(anode) during electrolysis.

ANOXIA
Deficient supply of oxygen to tissues.

ANTIBODY
A modified protein circulating in the serum of an animal, synthesized in response to a
foreign molecule (antigen) that has entered the body.

ANTIGEN
A foreign substance (usually a protein) that stimulates formation of antibody.

ASPHYXIA
The result of a diminished supply of oxygen to the blood and tissues and interference
with the respiratory function. Simple anoxia may be caused by ‘inert gases’, e.g. nitrogen, and
some flammable gases, e.g. methane. Toxic anoxia may be caused by certain substances, e.g.
carbon monoxide and hydrogen cyanide, which interfere with the body’s ability to transfer or
utilize oxygen in the tissues. Rapid unconsciousness and death can occur in either case.

ASTHMA
Periodic attacks of wheezing, chest tightness and breathlessness resulting from constriction
of the airways.

ATOM
The smallest unit of an element incapable of further subdivision in the course of a chemical
reaction.

ATOMIC NUMBER
The number of protons in an atomic nucleus.

ATOPY
Hypersensitivity where tendency to allergy is inherited.

AUTO-IGNITION TEMPERATURE
The minimum temperature required to initiate or cause self-sustained combustion of material in the absence of any external source of energy. (Values may change significantly with geometry, gas/vapour concentration, and presence of catalyst.) Any ignition source must be at a temperature of, or greater than, the ignition temperature of the specific substance.