Construction Safety and Health Outreach Program Glossary
U.S. Department of Labor,
Occupational Safety & Health Administration,
Constitution Avenue, NW,
Washington, DC 20210, U.S.A.
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American Conference of Governmental Industrial Hygienists,
which develops and publishes recommended occupational
exposure limits for hundreds of chemical substances
and physical agents. See TLV.
Any chemical with a low pH that in water solution
can burn the skin or eyes. Acids turn litmus paper
red and have pH values of 0 to 6.
Term used by OSHA and NIOSH to express the level of
toxicant which requires medical surveillance, usually
one half of the PEL.
Charcoal is an amorphous form of carbon formed by
burning wood, nutshells, animal bones, and other carbonaceous
materials. Charcoal becomes activated by heating it
with steam to 800-900oC. During this treatment,
a porous, submicroscopic internal structure is formed
which gives it an extensive internal surface area.
Activated charcoal is commonly used as a gas or vapor
adsorbent in air-purifying respirators and as a solid
sorbent in air-sampling.
Adverse effect on a human or animal which has severe
symptoms developing rapidly and coming quickly to
a crisis. Also see "chronic effect."
The condensation of gases, liquids, or dissolved substances
on the surfaces of solids.
American Industrial Hygiene Association.
The mixture of gases that surrounds the earth; its
major components are as follows: 78.08% nitrogen,
20.95% oxygen, 0.03% carbon dioxide, and 0.93% argon.
Water vapor (humidity) varies.
A respirator that is connected to a compressed breathing
air source by a hose of small inside diameter. The
air is delivered continuously or intermittently in
a sufficient volume to meet the wearer's breathing
A respirator that uses chemicals to remove specific
gases and vapors form the air or that uses a mechanical
filter to remove particulate matter. An air- purifying
respirator must only be used when there is sufficient
oxygen to sustain life and the air contaminant level
is below the concentration limits of the device.
Any chemical with a high pH that in water solution
is irritating or caustic to the skin. Strong alkalies
in solution are corrosive to the skin and mucous membranes.
Example: sodium hydroxide, referred to as caustic
soda or lye. Alkalis turn litmus paper blue and have
pH values from 8 to 14. Another term for alkali is
An abnormal response of a hypersensitive person to
chemical and physical stimuli. Allergic manifestations
of major importance occur in about 10 percent of the
The American National Standards Institute is a voluntary
membership organization (run with private funding)
that develops consensus standards nationally for a
wide variety of devices and procedures.
A vapor or gas which can cause unconsciousness or
death by suffocation (lack of oxygen). Asphyxiation
is one of the principal potential hazards of working
in confined spaces.
American Society for Testing and Materials.
A respirator that provides breathing air from a source
independent of the surrounding atmosphere. There are
two types: air-line and self-contained breathing apparatus.
The pressure exerted in all directions by the atmosphere.
At sea level, mean atmospheric pressure is 29.92 inches
Hg, 14.7 psi, or 407 inches w.g.
A compound that reacts with an acid to form a salt.
It is another term for alkali.
Not malignant. A benign tumor is one which does not
metastasize or invade tissue. Benign tumors may still
be lethal, due to pressure on vital organs.
A combination of the words biological hazard. Organisms
or products of organisms that present a risk to humans.
The temperature at which the vapor pressure of a liquid
equals atmospheric pressure.
A colorless, odorless toxic gas produced by any process
that involves the incomplete combustion of carbon-containing
substances. It is emitted through the exhaust of gasoline
A substance or agent capable of causing or producing
cancer in mammals, including humans. A chemical is
considered to be a carcinogen if: a) it has been evaluated
by the International Agency for Research on Cancer
(IARC) and found to be a carcinogen or potential carcinogen;
or b) it is listed as a carcinogen or potential carcinogen
in the Annual Report on Carcinogens published by the
National Toxicology Program (NTP) (latest edition);
or c) it is regulated by OSHA as a carcinogen.
Chemical Abstracts Service is an organization under
the American Chemical Society. CAS abstracts and indexes
chemical literature from all over the world in "Chemical
Abstracts." "CAS Numbers" are used
to identify specific chemicals or mixtures.
Ceiling limit (C).
An airborne concentration of a toxic substance in
the work environment, which should never be exceeded.
Comprehensive Environmental Response, Compensation
and Liability Act of 1980. Commonly known as "Superfund."
Chemical cartridge respirator.
A respirator that uses various chemical substances
to purify inhaled air of certain gases and vapors.
This type respirator is effective for concentrations
no more than ten times the TLV of the contaminant,
if the contaminant has warning properties (odor or
irritation) below the TLV.
Chemical Transportation Emergency Center. Public service
of the Chemical Manufacturers Association that provides
immediate advice for those at the scene of hazardous
materials emergencies. CHEMTREC has a 24-hour toll-free
telephone number (800-424-9300) to help respond to
chemical transportation emergencies.
An adverse effect on a human or animal body, with
symptoms which develop slowly over a long period of
time or which recur frequently. Also see "acute."
Combustible liquids are those having a flash point
at or above 37.8oC (100oF).
The amount of a given substance in a stated unit of
measure. Common methods of stating concentration are
percent by weight or by volume, weight per unit volume,
A substance that causes visible destruction or permanent
changes in human skin tissue at the site of contact.
Code of Federal Regulations. A collection of the regulations
that have been promulgated under United States Law.
Pertaining to or affecting the skin.
Degrees Celsius (Centigrade).
The temperature on a scale in which the freezing point
of water is 0oC and the boiling point is
100oC. To convert to Degrees Fahrenheit,
use the following formula: oF = (oC
x 1.8) + 32.
The temperature on a scale in which the boiling point
of water is 212oF and the freezing point
The mass per unit volume of a substance. For example,
lead is much more dense than aluminum.
Inflammation of the skin from any cause.
A broader term than dermatitis; it includes any cutaneous
abnormality, thus encompassing folliculitis, acne,
pigmentary changes, and nodules and tumors.
Correlation between the amount of exposure to an agent
or toxic chemical and the resulting effect on the
U.S. Department of Labor. OSHA and MSHA are part of
U.S. Department of Transportation.
Solid particles generated by handling, crushing, grinding,
rapid impact, detonation, and decrepitation of organic
or inorganic materials, such as rock, ore, metal,
coal, wood and grain. Dusts do not tend to flocculate,
except under electrostatic forces; they do not diffuse
in air but settle under the influence of gravity.
Shortness of breath, difficult or labored breathing.
U.S. Environmental Protection Agency.
The process by which a liquid is changed into the
The ratio of the time required to evaporate a measured
volume of a liquid to the time required to evaporate
the same volume of a reference liquid (butyl acetate,
ethyl ether) under ideal test conditions. The higher
the ratio, the slower the evaporation rate. The evaporation
rate can be useful in evaluating the health and fire
hazards of a material.
Publication of U.S. government documents officially
promulgated under the law, documents whose validity
depends upon such publication. It is published on
each day following a government working day. It is,
in effect, the daily supplement to the Code of Federal
The lowest temperature at which a material can evolve
vapors fast enough to support continuous combustion.
Emergency measures to be taken when a person is suffering
from overexposure to a hazardous material, before
regular medical help can be obtained.
Flammables have a minimum concentration below which
propagation of flame does not occur on contact with
a source of ignition. This is known as the lower flammable
explosive limit (LEL). There is also a maximum concentration
of vapor or gas in air above which propagation of
flame does not occur. This is known as the upper flammable
explosive limit (UEL). These units are expressed in
percent of gas or vapor in air by volume.
Any liquid having a flash point below 37.8oC
(100oF), except any mixture having components
with flashpoints of 100oF or higher, the
total of which make up 99 percent or more of the total
volume of the mixture.
The difference between the lower and upper flammable
limits, expressed in terms of percentage of vapor
or gas in air by volume, and is also often referred
to as the "explosive range."
The minimum temperature at which a liquid gives off
vapor within a test vessel in sufficient concentration
to form an ignitable mixture with air near the surface
of the liquid. Two tests are used - open cup and closed
Airborne particulate formed by the evaporation of
solid materials, e.g. metal fume emitted during welding.
Usually less than one micron in diameter.
Pressure measured with respect to atmospheric pressure.
A state of matter in which the material has very low
density and viscosity; can expand and contract greatly
in response to changes in temperature and pressure;
easily diffuses into other gases; readily and uniformly
distributes itself throughout any container. A gas
can be changed to the liquid or solid state only by
the combined effect of increased pressure and decreased
temperature. Examples include sulfur dioxide, ozone,
and carbon monoxide.
A metric unit of weight. One ounce equals 28.4 grams.
(High Efficiency Particulate Air Filter) A disposable,
extended medium, dry type filter with a particle removal
efficiency of no less than 99.97 percent for 0.3m
International Agency for Research on Cancer.
Immediately Dangerous to Life and Health. An atmospheric
concentration of any toxic, corrosive or asphyxiant
substance that poses an immediate threat to life or
would cause irreversible or delayed adverse health
effects or would interfere with an individual's ability
to escape from a dangerous atmosphere.
Anything that provides heat, spark or flame sufficient
to cause combustion/explosion.
The minimum temperature to initiate or cause self-sustained
combustion in the absence of any source of ignition.
A material that does not allow another substance to
pass through or penetrate it. Frequently used to describe
Inches of mercury column.
A unit used in measuring pressures. One inch of mercury
column equals a pressure of 1.66 kPa (0.491 psi).
Inches of water column.
A unit used in measuring pressures. One inch of water
column equals a pressure of 0.25 kPa (0.036 psi).
Materials which could cause dangerous reactions from
direct contact with one another.
Taking in by the mouth.
Breathing of a substance in the form of a gas, vapor,
fume, mist, or dust.
Incapable of being dissolved in a liquid.
A chemical, which is not corrosive, but which causes
a reversible inflammatory effect on living tissue
by chemical action at the site of contact.
The time that elapses between exposure and the first
manifestation of damage.
Lethal concentration that will kill 50 percent of
the test animals within a specified time. See LD50.
The dose required to produce the death in 50 percent
of the exposed species within a specified time.
A measure of capacity - one quart equals 0.9L.
Lower explosive limit (LEL).
The lower limit of flammability of a gas or vapor
at ordinary ambient temperatures expressed in percent
of the gas or vapor in air by volume. This limit is
assumed constant for temperatures up to 120oC
(250oF). Above this, it should be decreased
by a factor of 0.7 because explosibility increases
with higher temperatures.
As applied to a tumor. Cancerous and capable of undergoing
metastasis, or invasion of surrounding tissue.
Transfer of the causal agent (cell or microorganism)
of a disease from a primary focus to a distant one
through the blood or lymphatic vessels. Also, spread
of malignancy from site of primary cancer to secondary
A metric unit of length, equal to about 39 inches.
Micron (micrometer, m).
A unit of length equal to one millionth of a meter,
approximately 1/25,000 of an inch.
A unit of weight in the metric system. One thousand
milligrams equals one gram.
Milligrams per cubic meter (mg/m3).
Unit used to measure air concentrations of dusts,
gases, mists, and fumes.
A metric unit used to measure volume. One milliliter
equals one cubic centimeter.
Millimeter of mercury (mmHg).
The unit of pressure equal to the pressure exerted
by a column of liquid mercury one millimeter high
at a standard temperature.
Suspended liquid droplets generated by condensation
from the gaseous to the liquid state or by breaking
up a liquid into a dispersed state, such as by splashing,
foaming, or atomizing. Mist is formed when a finely
divided liquid is suspended in air.
Material Safety Data Sheet.
Mine Safety and Health Administration, U.S. Department
Lining of the hollow organs of the body, notably the
nose, mouth, stomach, intestines, bronchial tubes,
and urinary tract.
The National Fire Protection Association is a voluntary
membership organization whose aim is to promote and
improve fire protection and prevention. The NFPA publishes
16 volumes of codes known as the National Fire Codes.
The National Institute for Occupational Safety and
Health is a federal agency. It conducts research on
health and safety concerns, tests and certifies respirators,
and trains occupational health and safety professionals.
National Toxicology Program. The NTP publishes an
Annual Report on carcinogens.
Have a long history of little adverse effect on the
lungs and do not produce significant organic disease
or toxic effect when exposures are kept under reasonable
U.S. Occupational Safety and Health Administration,
U.S. Department of Labor.
A substance that gives up oxygen readily. Presence
of an oxidizer increases the fire hazard.
That concentration of oxygen by volume below which
atmosphere supplying respiratory protection must be
provided. It exists in atmospheres where the percentage
of oxygen by volume is less than 19.5 percent oxygen.
An atmosphere containing more than 23.5 percent oxygen
A suspension of fine solid or liquid particles in
air, such as dust, fog, fume, mist, smoke or sprays.
Particulate matter suspended in air is commonly known
as an aerosol.
Permissible exposure limit. An exposure limit that
is published and enforced by OSHA as a legal standard.
Personal protective equipment (PPE).
Devices worn by the worker to protect against hazards
in the environment. Respirators, gloves, and hearing
protectors are examples.
Means used to express the degree of acidity or alkalinity
of a solution with neutrality indicated as seven.
A chemical reaction in which two or more small molecules
(monomers) combine to form larger molecules (polymers)
that contain repeating structural units of the original
molecules. A hazardous polymerization is the above
reaction, with an uncontrolled release of energy.
Parts per million parts of air by volume of vapor
or gas or other contaminant. Used to measure air concentrations
of vapors and gases.
Pounds per square inch (for MSDS purposes) is the
pressure a material exerts on the walls of a confining
vessel or enclosure. For technical accuracy, pressure
must be expressed as psig (pounds per square inch
gauge) or psia (pounds per square absolute; that is,
gauge pressure plus sea level atmospheric pressure,
or psig plus approximately 14.7 pounds per square
Resource Conservation and Recovery Act of 1976. (U.S.EPA)
A substance's susceptibility to undergo a chemical
reaction or change that may result in dangerous side
effects, such as an explosion, burning, and corrosive
or toxic emissions.
Respirable size particulates.
Particulates in the size range that permits them to
penetrate deep into the lungs upon inhalation.
A device which has met the requirements of 30 CFR
Part 11 and is designed to protect the wearer from
inhalation of harmful atmospheres and has been approved
by the National Institute for Occupational Safety
and Health (NIOSH) and the Mine Safety and Health
Consists of (in descending order) - the nose, mouth,
nasal passages, nasal pharynx, pharynx, larynx, trachea,
bronchi, bronchioles, air sacs (alveoli) of the lungs,
and muscles of respiration.
Route of entry.
The path by which chemicals can enter the body. There
are three main routes of entry: inhalation, ingestion,
and skin absorption.
Superfund Amendments and Reauthorization Act of 1986.
Self-contained breathing apparatus.
A substance which on first exposure causes little
or no reaction but which on repeated exposure may
cause a marked response not necessarily limited to
the contact site. Skin sensitization is the most common
form of sensitization in the industrial setting.
Short-term exposure limit (STEL).
ACGIH-recommended exposure limit. Maximum concentration
to which workers can be exposed for a short period
of time (15 minutes) for only four times throughout
the day with at least one hour between exposures.
A notation (sometimes used with PEL or TLV exposure
data) which indicates that the stated substance may
be absorbed by the skin, mucous membranes, and eyes
-- either airborne or by direct contact -- and that
this additional exposure must be considered part of
the total exposure to avoid exceeding the PEL or TLV
for that substance.
Solubility in water.
A term expressing the percentage of a material (by
weight) that will dissolve in water at ambient temperature.
Solubility information can be useful in determining
spill cleanup methods and re-extinguishing agents
and methods for a material.
A substance, usually a liquid, in which other substances
are dissolved. The most common solvent is water.
(1) A material that a removes toxic gases and vapors
from air inhaled through a canister or cartridge.
(2) Material used to collect gases and vapors during
The ratio of the mass of a unit volume of a substance
to the mass of the same volume of a standard substance
at a standard temperature. Water at 4oC
(39.2oF) is the standard usually referred
to for liquids; for gases, dry air (at the same temperature
and pressure as the gas) is often taken as the standard
substance. See Density.
An expression of the ability of a material to remain
unchanged. For MSDS purposes, a material is stable
if it remains in the same form under expected and
reasonable conditions of storage or use. Conditions
which may cause instability (dangerous change) are
stated. Examples are temperatures above 150oF,
shock from dropping.
Cooperative action of substances whose total effect
is greater than the sum of their separate effects.
Spread throughout the body, affecting all body systems
and organs, not localized in one spot or area.
The lowest dose or exposure to a chemical at which
a specific effect is observed.
Time-weighted average concentration
Refers to concentrations of airborne toxic materials
which have been weighted for a certain time duration,
usually 8 hours.
A time-weighted average concentration under which
most people can work consistently for 8 hours a day,
day after day, with no harmful effects. A table of
these values and accompanying precautions is published
annually by the American Conference of Governmental
A relative property of a chemical agent and refers
to a harmful effect on some biologic mechanism and
the conditions under which this effect occurs.
Upper explosive limit (UEL).
The highest concentration (expressed in percent vapor
or gas in the air by volume) of a substance that will
burn or explode when an ignition source is present.
Pressure (measured in pounds per square inch absolute
- psia) exerted by a vapor. If a vapor is kept in
confinement over its liquid so that the vapor can
accumulate above the liquid (the temperature being
held constant), the vapor pressure approaches a fixed
limit called the maximum (or saturated) vapor pressure,
dependent only on the temperature and the liquid.
The gaseous form of substances that are normally in
the solid or liquid state (at room temperature and
pressure). The vapor can be changed back to the solid
or liquid state either by increasing the pressure
or decreasing the temperature alone. Vapors also diffuse.
Evaporation is the process by which a liquid is changed
into the vapor state and mixed with the surrounding
air. Solvents with low boiling points will volatilize
readily. Examples include benzene, methyl alcohol,
mercury, and toluene.
The property of a fluid that resists internal flow
by releasing counteracting forces.
The tendency or ability of a liquid to vaporize. Such
liquids as alcohol and gasoline, because of their
well-known tendency to evaporate rapidly, are called
A unit used in measuring pressure. See also Inches
of water column.
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