Thompson Rivers University
Thompson Rivers University

MSDS Terminology

Some important terms used in MSDS's are briefly discussed below:

Term Description
Acute Exposure A single exposure to a substance or multiple exposures occurring within a short time, usually 24 hours or less.
Allergens Substances which trigger the body's immune response and produce an allergic response.
Asphyxiants Substances which replace oxygen, eventually making breathing impossible.
Auto-ignition Temperature Temperature at which the vapour from a liquid will ignite without a source of ignition such as a spark or flame.
Carcinogens Substances or agents capable of causing cancer in mammals.
Ceiling Exposure Limit
[C or CEL]
The maximum concentration of a chemical to which one may be exposed at any time. This value is never to be exceeded without special precautions.
Chronic Exposure Repeated exposure to a substance over a relatively long period of time [typically more than ten per cent of lifetime in laboratory studies].
Combustible Liquid Liquids with flash points 100 F [37.8 C] or more, but less than 93.3 F [200 C] when tested in accordance with an established procedure.
Flammable Limits The upper and lower concentrations of a gas or vapour in air between which an explosion or propagation of flame will occur when an ignition source is present.
Flammable Liquid A liquid with a flash point below 100 F [38.7 C.] when tested in accordance with an established procedure.
Flash Point The minimum temperature at which a liquid gives off enough vapour to ignite in the presence of a source of ignition under specified test conditions.
Half Life The period of time for a chemical or radioactive substance to lose half its concentration or activity due to metabolic uptake, decay, or other chemical change.
I.D.L.H. Immediately Dangerous to Life and Health. An atmosphere where the concentration of oxygen or flammable or toxic air contaminants would cause a person without respiratory protection to be fatally injured or would cause irreversible and incapacitating effects on that person's health.
Irritants Substances which cause reddening, itching or pain to exposed bodily parts.
LC50 and LD50 These are not exposure criteria, but represent the concentrations taken orally or inhaled, which killed about 50% of a test population. One need not remember the exact meaning of the terms. It is useful however, to know that a low LC or LD50 quantity indicates the relative toxicity of a substance.
Mutagen Substances that cause genetic mutation in living cells. May occur in either reproductive or body cells.
Odour Threshold The lowest airborne concentration of a chemical that can be perceived by the sense of smell.
Pictogram Refers to the stylized graphical material which appears within a hazard symbol.
Poisons Any substances which injurious to health when taken into the body.
Polymerization A chemical reaction in which one or more small molecules combine to form larger molecules. A hazardous polymerization is one that takes place at a rate which releases large amounts of energy.
Risk Phrase A statement identifying a hazard that may arise from the nature of the controlled product or the class, division or subdivision of controlled products.
Sensitizer A substance which on first exposure causes little or no reaction in man or test animals, but which on repeated exposure may cause a marked response not necessarily limited to the contact site. Skin sensitization is the most common form in industry, although respiratory tract sensitization also occurs.
Short Term Exposure Limit [STEL] The maximum exposure limit to which one may exposed for a brief (generally 15 minute) period for a maximum of 4 such periods per day, without suffering serious health effects.
Solvent A liquid which will dissolve another substance.
Synergist An agent or substance that augments or increases the activity or effects of another agent or substance. Often increases the dangerous effects of the mixture.
TDG Refers to Transportation of Dangerous Goods Act
Teratogen Substances which deform a fetus or cause birth defects.
Threshold Limit Value Threshold Limit Value is a term used by the American Conference of Governmental Industrial Hygienists [ACGIH] to express the airborne concentration of a material to which nearly all persons can be exposed day after day, without adverse effects.
Time Weighted Average [TWA] The airborne concentration of a substances to which a person is exposed when calculated as a weighted average over a period of time [usually 8 hours].
Vapour The gaseous form of a substance that is found in a solid or liquid state at normal atmospheric pressure.
Vapour Pressure The pressure exerted by a saturated vapour above its own liquid in a closed container.
Ventilation - exhaust Considered as either "general" or "local" exhaust ventilation, and involve mechanical systems which are designed, installed and maintained for the control of airborne contaminants. Local exhaust systems are preferred for the control of harmful substances. Designs should be in accordance with established ventilation principles produced by the American Conference of Government Industrial Hygienists.
Warning Properties The capability of chemicals to be noticed by human senses at levels in the air below those which may cause ill health effects.