GLOSSARY OF MSDS TERMS
Acute Exposure - a short-term exposure usually occurring
at high concentration.
Acute Health Effect - an effect that develops either
immediately or a short time after exposure.
Antidote - a remedy or other agent to counteract the
effects of a poison.
Atomic Weight - The average weight of an atom of an
element, usually expressed relative to one atom of the carbon
isotope taken as a weight of 12.
Autoignition Temperature - the minimum temperature
required to initiate or cause self-sustained combustion, in the
absence of a spark or flame.
Biohazardous Infectious Material - a material that
contains organisms and the toxins produced by these organisms that
have been shown to cause disease or are believed to cause disease in
either humans or animals.
Boiling Point - the temperature at which a liquid changes
from a liquids to a gas, at normal atmospheric pressure.
Carcinogens - agents/compounds that may induce cancer in
CAS Registry Number - a number assigned to a material by
the Chemical Abstracts Service (CAS) to provide a single
Chemical Formula - sometimes called the molecular formula,
indicates the elements that make up a chemical.
Chemical Name - a proper scientific name for the active
ingredient of a product.
Chronic Exposure - a long-term exposure, usually occurring
at low concentrations.
Chronic Health Effects - an effect that appears a long
time after exposure.
Coefficient of Oil/Water Distribution - the ratio of the
solubility of the chemical in an oil to its solubility in water.
Combustible Liquid - a liquid which has a flash point
above 37.8 C.
Compressed Gas - a material which is a gas at normal room
temperature (20 C) and pressure but is packaged as a
pressurized gas, dissolved gas or gas liquefied by compression or
Condensation - the process of reducing from one form to
another denser form such as steam to water.
Controlled Products - Under the Controlled Products
Regulation, a controlled product is defined as a material, product
or substance which is imported or sold in Canada and meets the
criteria for one or more of the following classes: -
- Class A - Compressed Gas
- Class B - Flammable and Combustible Material
- Class C - Oxidizing Material
- Class D - Poisonous and Infectious Material
- Class E - Corrosive Material
- Class F - Dangerously Reactive Material
Corrosive Material - a material that can attack (corrode)
metals or cause permanent damage to human tissues such as skin and
eyes on contact.
Cryogenics - materials which exist at extremely low
temperatures, such as liquid nitrogen.
Dangerously Reactive Materials - materials that may
undergo vigorous condensation, decomposition or polymerization. They
may react violently under conditions of shock or increase in
pressure or temperature. They may also react vigorously with water
or water vapor to release a toxic gas.
Decomposition - the breakdown of a substance, often due to
heat, decay or other effect, with the release of other compounds
such as vapors or gases that may be flammable or toxic.
Density - the weight of a material in a given volume. It
is usually given in grams per millilitre (g/ml).
Dilution Ventilation - dilution of contaminated air with
uncontaminated air in a general area, room or building for the
purposes of health hazard or nuisance control, and/or for heating
Dose - amount of the agent that has entered the body
through the various routes of entry.
Evaporation Rate - the rate at which a liquid changes to
vapor at normal room temperature.
Explosive (Flammable) Limits - the lower explosive (flammable)
limit (LEL) is the lowest concentration of vapor in air which
will burn or explode upon contact with a source of ignition. The
upper explosive (flammable) limit (UEL) is the highest
concentration of vapor in air which will burn or explode upon
contact with a source of ignition.
Explosive (Flammable) Range - the range between the lower
explosive limit (LEL) and the upper explosive limit (UEL).
Exposure Limits- established concentrations which, if not
exceeded, will not generally cause adverse effects to the worker
exposed. Exposure limits differ in name and meaning depending on
origin. For example:-
- The exposure levels for the hazardous chemicals that are
included in the Regulation respecting the Control of Exposure to
Biological or Chemical Agents - made under the Occupational
Health and Safety Act of Ontario, are expressed as follow: -
TWAEV Time-Weighted Average Exposure Value: The
average airborne concentration of a biological or chemical agent
to which a worker may be exposed in a work day or a work week.
STEV Short Term Exposure Value: - The maximum
airborne concentration of a chemical or biological agent to
which a worker may be exposed in any 15 minute period, provided
the TWAEV is not exceeded.
CEV Ceiling Exposure Value: The maximum
airborne concentration of a biological or chemical agent to
which a worker may be exposed at any time.
SKIN: This notation indicates that direct or airborne
contact with the product may result in significant absorption of
the product through the skin, mucous membranes or eyes.
Inclusion of this notation is intended to suggest that
preventative action be taken against absorption of the agent
through these routes of entry.
- Threshold Limit Values (TLVs) are exposure guidelines
developed by the American Conference of Governmental Industrial
Hygienists (ACGIH). They have been adopted by several Canadian
governments and others as their legal limits. They are expressed
TLV-TWA Threshold Limit Value - Time-Weighted Average:
The time-weighted average concentration for a normal 8 hour work
day and a 40 hour work week, to which nearly all workers may be
repeatedly exposed, day after day, without adverse effect.
TLV-STEL Threshold Limit Value - Short Term
Exposure Limit: a 15 minute time-weighted average exposure
which should not be exceeded at any time during a work day even
if the 8 hr TWA is within the TLV. Exposures at the STEL should
not be repeated more than 4 times a day and there should be at
least 60 minutes between successive exposures at the STEL.
TLV-C Threshold Limit Value - Ceiling: the
concentration that should not be exceeded during any part of the
Other exposure limits include the Permissible Exposure Limits
(PEL) which are legal exposure limits in the United
Flammable Limits - "See Explosive Limits".
Flammable Substance - one that will readily catch fire and
continue to burn in air if exposed to a source of ignition.
- Flammable Aerosol- a material that is packaged in an
aerosol container which can release a flammable material.
- Flammable Gas- a gas which can readily catch fire and
continue to burn.
- Flammable Liquid - a material that gives off a vapor
which can readily catch fire and continue to burn. A flammable
liquid has a flashpoint below 37.8 C.
- Flammable Solid- a material which can readily catch
fire and continue to burn vigorously and persistently. This may
occur from friction, absorbing moisture, from spontaneous
chemical change, or by retaining heat from manufacturing or
- Reactive Flammable Material- a material which is a
dangerous fire risk because it can react readily with air or
Flashback - this occurs when a trail of flammable material
is ignited by a distant source of ignition. The flame then travels
back along the trail of gas, vapor or aerosol to its source.
Flashpoint - the lowest temperature of a liquid at which
it gives off enough vapor to form an ignitable mixture of vapor and
air immediately above the liquid surface.
Freezing Point - the temperature at which a liquid becomes
a solid, at normal atmospheric pressure.
Hazard- the potential for harmful effects.
Hazardous Combustion Products - chemicals which may be
formed when a material burns. These chemicals may be flammable,
toxic or have other hazards.
Hazardous Decomposition Products - formed when a material
decomposes (breaks down) because it is unstable, or reacts
with materials such as water or oxygen in air.
Hazardous Ingredient - Under the Hazardous Products Act, a
chemical must be listed in the Hazardous Ingredients section of a
- it meets the criteria for a controlled product;
- it is on the Ingredient Disclosure List;
- there is no toxicological information available; or
- the supplier has reason to believe it might be hazardous.
Hazardous Polymerization - Polymerization is a process of
forming a polymer by combining large numbers of chemical units or
monomers into long chains (polyethylene from ethylene or
polystyrene from styrene). Uncontrolled polymerization can be
extremely hazardous. Some polymerization processes can release
considerable heat or can be explosive.
Ingestion - means taking a material into the body by mouth
Inhalation - means taking a material into the body by
breathing it in.
Irritant - some sort of aggravation of whatever tissue the
material comes in contact with.
LC50 - the concentration of a material in air which causes
death in 50% of a group of test animals. The material is inhaled
over a set period of time, usually 4 hrs. LC stands for lethal
LD50 - the weight of material which causes the death in
50% of a group of test animals. It is usually expressed in weight of
material per weight of test animal. LD stands for lethal dose.
LEL (Lower Explosive Limit) - See "Explosive Limits".
Local Exhaust Ventilation - involves the capture of
pollutants at the source.
Material Causing Immediate and Serious Toxic Effects -
classified under "Poisonous and Infectious Material" as toxic or
very toxic based on information such as the LD50 or LC50.
Material Causing Other Toxic Effects - classified under
"Poisonous and Infectious Material" as a material causing toxic
effects such as skin or respiratory sensitization, carcinogenicity,
Melting Point - the temperature at which a solid material
becomes a liquid.
Molecular Formula - A chemical formula that shows the
number of atoms of each element in a molecule of a compound.
Molecular Weight - the sum of the atomic weights of a
molecule's constituent atoms.
Mutagen - an agent that affects the genes or cells of the
exposed people in such a way that it may cause cancer in the exposed
individual or an undesirable mutation to occur in some later
NA Number - See "UN number".
Odor Threshold - the airborne concentration, usually in
part per million, at which an odor becomes noticeable.
Oxidizing Material - gives up oxygen easily or can readily
oxidize other materials.
Permissible Exposure Limits (PEL) - legal limits in the
U.S.A. set by the Occupational Safety and Health Administration (OSHA).
pH - a measure of the acidity or basicity (alkalinity)
of a material when dissolved in water.
Polymer - a natural or man-made material formed by
combining units, called monomers, into long chains.
Polymerization - a process of forming a polymer by
combining large numbers of chemical units or monomers into long
Parts Per Million (ppm) - represents the concentration of
gases or vapor in air. For example, 1 ppm of a gas means that 1 unit
of the gas is present for every 1 million units of air.
Reactivity - tendency to participate in chemical reactions.
Sensitization - the development, over time, of an allergic
reaction to a chemical.
Solubility - the ability of a material to dissolve in
water or another liquid.
Solvent - a material which is capable of dissolving
Specific Gravity - the density of a liquid compared to the
density of an equal amount of water.
Stability - the ability of a material to remain unchanged
in the presence of heat, moisture or air.
Teratogen - agents or compounds that a pregnant woman
takes into her body that generate defects in the fetus.
TLV - See "exposure Limits".
Toxicity - ability of a substance to cause harmful
Trade Name - the name under which a product is
TWA - See "Exposure Limits".
UEL (Upper Explosive Limits) - See "Explosive Limits".
UN Number - a four digit number assigned to a potentially
hazardous material or class of materials. UN (United Nations)
numbers are internationally recognized and are used by fire fighter
and other emergency response personnel for identification of
materials during transportation emergencies. NA (North American)
numbers are assigned by Transport Canada and the US Department of
Transport to materials they consider hazardous and to which a UN
number has not been assigned.
Vapor - a gaseous form of a material which is normally
solid or liquid at room temperature and pressure.
Vapor Density - the density of a vapor compared to the
density of an equal amount of air.
Vapor Pressure - the pressure of a vapor in equilibrium
with its liquid or solid form.
Ventilation - the movement of air.
Volatility - the ability of a material to evaporate.