A concentration for a specific substance, calculated as an eight (8)
hour time-weighted average, which initiates certain required activities such as exposure
monitoring and medical surveillance. Typically it is one-half that of the PEL for that
substance.
ACGIH
The American Conference of Governmental Industrial Hygienists is a
voluntary organization of professional industrial hygiene personnel in government or educational
institutions. The ACGIH develops and publishes recommended occupational exposure limits each
year called Threshold Limit Values (TLVs) for hundreds of chemicals, physical agents, and
biological exposure indices.
Acute Exposure
Single exposure episodes which occur over a short time
period.
ANSI
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.
ASHRAE
American Society of Heating, Refrigeration and Air Conditioning
Engineers.
Asphyxiant
A chemical (gas or vapor) that can cause death or unconsciousness by
suffocation. Simple asphyxiants such as nitrogen, either use up or displace oxygen in the air.
They become especially dangerous in confined or enclosed spaces. Chemical asphyxiants, such as
carbon monoxide and hydrogen sulfide, interfere with the body's ability to absorb or transport
oxygen to the tissues.
Any liquid having a flashpoint at or
above 100°F (37.8°C), but below 200°F (93.3°C), except any mixture
having components with flashpoints of 200°F (93.3°C), or higher, the total volume
of which make up 99 percent or more of the total volume of the mixture.
Corrosive
Any gas, liquid, or solid that causes destruction of human tissue or a
liquid that has a severe corrosion rate on steel. Generally, a substance that has a very low or a
very high pH.
Cutaneous
Pertain to or affecting the skin.
Decomposition
The breakdown of a chemical or substance into different parts or
simpler compounds. Decomposition can occur due to heat, chemical reaction, decay, etc.
Dermal
Pertaining to or affecting the skin.
Dermatitis
An inflammation of the skin.
Designated Area
An area which may be used for work with "select
carcinogens, reproductive toxins, or substances which have a high degree of acute toxicity."
A designated area may be the entire laboratory, an area of a laboratory, or a device such as a
laboratory hood. A designated area shall be placarded to reflect the designated hazard.
Dose
The concentration of a substance and the time period during which the
exposure occurs. The dose received links hazard and toxicity.
DOT
The United States Department of Transportation is the federal agency that
regulates the labeling and transportation of hazardous materials.
Dyspnea
Shortness of breath; difficult or labored breathing.
Emergency Spills
Accidental chemical discharges that present an immediate
danger to personnel and/or the environment. Under these circumstances, leave the spill site
immediately and send for help. Management of these spills is the responsibility of specially trained
and equipped personnel.
Employee
An individual employed in a laboratory work place who may be
exposed to hazardous materials in the course of his or her assignments.
EPA
The Environmental Protection Agency is the governmental agency
responsible for administration of laws to control and/or reduce pollution of air, water, and land
systems.
EPA Number
The number assigned to chemicals regulated by the Environmental
Protection Agency (EPA).
Erythema
A reddening of the skin.
Fires
Class A
Fires in ordinary combustible materials such as
wood, cloth, paper, rubber, and many plastics.
Class B
Fires in flammable liquids, oils, greases, tars,
oil-base paints, lacquers and flammable gases.
Class C
Fires that involve energized electrical equipment
where the electrical conductivity of the extinguishing medium
is of importance; when electrical equipment is de-energized, extinguishers
for class A or B fires may be safely used.
Class D
Fires in combustible metals such as potassium,
sodium, lithium, magnesium, titanium, zirconium.
Flammable
Any substance which may be classified as a flammable aerosol,
flammable gas, flammable liquid or flammable solid.
An aerosol that, when tested by the
method described in 16 CFR 1500.45, yields a flame protection exceeding 18 inches at full valve
opening, or a flashback (a flame extending back to the valve) at any degree of valve opening.
A gas that, at ambient temperature and
pressure, forms a flammable mixture with air at a concentration of 13 percent by volume or less;
or a gas that, at ambient temperature and pressure, forms a range of flammable mixtures with air
wider that 12 percent by volume, regardless of the lower limit.
Any liquid having a flashpoint below
100°F (37.8°C), except any mixture having components with flashpoints of
100°F (37.8°C), or higher, the total volume of which make up 99 percent or more of
the total volume of the mixture.
A solid, other than a blasting agent or
explosive, that is liable to cause fires through friction, absorption of moisture, spontaneous
chemical change, retained heat from processing, or which can be ignited readily, and when ignited
burns so vigorously and persistently as to create a serious hazard. A chemical shall be considered
a flammable solid if, when tested by the method described in 16 CFR 1500.44, it ignites and burns
with a self-sustained flame at a rate greater than one-tenth of an inch per second along its major
axis.
Flash Point
The minimum temperature at which a liquid gives off enough vapors
that will ignite and flash-over but will not continue to burn without the addition of more heat.
Hazard
The possibility that exposure to a substance will cause injury when a
specific quantity is used under certain conditions.
Health Hazard
A substance for which there is statistically significant evidence
based on at least one study conducted in accordance with established scientific principles that
acute or chronic health effects may occur in exposed employees. This term includes carcinogens,
toxic or highly toxic agents, reproductive toxins, irritants, corrosives, sensitizers, hepatotoxins,
nephrotoxins, neurotoxins, agents which act on the hematopoietic systems, and agents which
damage the lungs, skin, eyes, or mucous membranes.
ICP
Inductively-coupled argon spectrometers
IDLH
Immediately dangerous to life or health concentrations represent the
maximum concentration from which one could escape within 30 minutes without a respirator and
without experiencing any escape-impairing (e.g., severe eye irritation) or irreversible health
effects.
Ignitable
A solid, liquid, or compressed gas that has a flashpoint of less
140°F. Ignitable material may be regulated by the EPA as a hazardous waste, as well.
Incompatible
The term applied to two substances to indicate that one material
cannot be mixed with the other without the possibility of a dangerous reaction.
Ingestion
Taking a substance into the body through the mouth as food, drink,
medicine, or unknowingly as on contaminated hands or cigarettes, etc.
Inhalation
The breathing in of an airborne substance that may be in the form of
gases, fumes, mists, vapors, dusts, or aerosols.
Inhibitor
A substance that is added to another to prevent or slow down an
unwanted reaction or change.
Irritant
A substance that produces an irritating effect when it contacts skin, eyes,
nose, or respiratory system.
LC50See Lethal Concentration 50.
LD50
See Lethal Dose 50.
LEL
See Lower Explosive Limit.
Lethal Concentration 50
The concentration of an air contaminant that will kill 50
percent of the test animals in a group during a single exposure.
Lethal Dose 50
The dose of a substance or chemical that will kill 50 percent of
the test animals in a group within the first 30 days following exposure.
LEL
See Lower Explosive Limit.
Lower Explosive Limit
(Also known as Lower Flammable Limit.) The lowest
concentration of a substance that will produce a fire or flash when an ignition source (flame,
spark, etc.) is present. It is expressed in percent of vapor or gas in the air by volume. Below the
LEL or LEL, the air/contaminant mixture is theoretically too "lean" to burn. (See also
UEL.)
Minor Spills
Small chemical leaks that usually are detected early and present no
immediate danger to personnel or the environment. These are spills that can be safely corrected
with the advice of knowledgeable laboratory or supervisory personnel.
Anything that can cause a change (or mutation) in the genetic material
of a living cell.
Narcosis
Stupor or unconsciousness caused by exposure to a chemical.
NFPA
The National Fire Protection Association is a voluntary membership
organization whose aims are to promote and improve fire protection and prevention. NFPA has
published several volumes of codes known as the National Fire Codes.
NIH
National Institute of Health
NIOSH
The National Institute for Occupational Safety and Health is a federal
agency that among its various responsibilities trains occupational health and safety professionals,
conducts research on health and safety concerns, and test and certifies respirators for work place
use.
Odor Threshold
The minimum concentration of a substance in the air at which a
majority of test subjects can detect and identify the substance's characteristic odor.
OSHA
The Occupational and Safety Health Administration is a federal or state
agency under the Department of Labor that publishes and enforces safety and health regulations
for most businesses and industries in the United States.
Oxidizer
A substance such as chlorate, permanganate, inorganic peroxide,
nitrocarbonitrate, or a nitrate that yields oxygen readily to stimulate the combustion of organic
matter.
Oxygen Deficiency
An atmosphere having less than the normal percentage of
oxygen found in normal air. Normal air contains approximately 21% oxygen at sea level.
PEL
See Permissible Exposure Limit.
Permissible Exposure Limit
An exposure limit that is published and enforced by
OSHA as a legal standard. PEL may be either a time-weighted-average (TWA) exposure limit (8
hour), a 15-minute short term exposure limit (STEL), or a ceiling (C). The PELs are found in
Tables Z-1, Z-2, or Z-3 of 29 CFR 1910.100. This level of exposure is deemed to be the
maximum safe concentration and is generally the same value as the threshold limit value
(TLV).
Personal Protective Equipment
Any devices or clothing worn by the worker to
protect against hazards in the environment. Examples are respirators, gloves, and chemical splash
goggles.
Physical Hazard
A substance which is a compressed gas, explosive, flammable,
organic peroxide, oxidizer, pyrophoric, unstable or water reactive.
Polymerization
A chemical reaction in which two or more small molecules
combine to form larger molecules that contain repeating structural units of the original molecules.
A hazardous polymerization is the above reaction with an uncontrolled release of energy.
Reactivity
A substance's susceptibility to undergoing a chemical reaction or
change that may result in dangerous side effects, such as explosion, burning, and corrosive or
toxic emissions. The conditions that cause the reaction, such as heat, other chemicals, and
dropping, will usually be specified as "Conditions to Avoid" when a chemical's
reactivity is discussed on a MSDS.
Respirator
A device which is designed to protect the wearer from inhaling
harmful contaminants.
Respiratory Hazard
A particular concentration of an airborne contaminant that,
when it enters the body by way of the respiratory system or by being breathed into the lungs,
results in some bodily function impairment.
A transparent, easily-movable, horizontal sliding or
vertical rising panel that can substantially close off a laboratory fume hood face, designed to be a
safety barrier between the fume hood operator and the interior of the hood.
Sensitizer
A substance that may cause no reaction in a person during initial
exposures, but afterwards, further exposures will cause an allergic response to the substance.
Sharps
hypodermic needles, syringes, (with or without the attached needle),
pasteur pipettes, scalpel blades, suture needles, blood vials, needles with attached tubing, and
culture dishes (regardless of presence of infectious agents). Also included are other types of
broken or unbroken glassware that were in contact with infectious agents, such as used slides and
cover slips.
Short Term Exposure Limit
Represented as STEL or TLV-STEL, this is the
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.
" SKIN "
This designation sometimes appears alongside a TLV or
PEL. It refers to the possibility of absorption of the particular chemical through the skin and eyes.
Thus, protection of large surface areas of skin should be considered to prevent skin absorption so
that the TLV is not invalidated.
STEL
See Short Term Exposure Limit
Synonym
Another name by which the same chemical may be known.
Systemic
Spread throughout the body; affecting many or all body systems or
organs; not localized in one spot or area.
Teratogen
An agent or substance that may cause physical defects in the
developing embryo or fetus when a pregnant female is exposed to that substance.
Threshold Limit Value
Airborne concentrations of substances devised by the
ACGIH that represents conditions under which it is believed that nearly all workers may be
exposed day after day with no adverse effect. TLVs are advisory exposure guidelines, not legal
standards, that are based on evidence from industrial experience, animal studies, or human studies
when they exist. There are three different types of TLV's: Time Weighted Average (TLV-TWA),
Short Term Exposure Limit (TLV-STEL) and Ceiling (TLV-C). (See also PEL.)
Time Weighted Average
(TLV-TWA, Threshold Limit Value-Time Weighted
Average) The time weighted average airborne chemical concentration for a normal eight 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
See Threshold Limit Value.
Toxic
Substances such as carcinogens, irritants, or poisonous gases, liquids, and
solids which are irritating to or affect the health of humans.
Toxicity
The potential of a substance to exert a harmful effect on humans or
animals and a description of the effect and the conditions or concentrations under which the effect
takes place.
Trade Name
The commercial name or trademark by which a chemical is known.
One chemical may have a variety of trade names depending on the manufacturers or distributors
involved.
TWASee Time Weighted Average.
UEL
See Upper Explosive Limit.
UEL
See Upper Explosive Limit.
Unstable Liquid
A liquid that, in its pure state or as commercially produced, will
react vigorously in some hazardous way under shock conditions (i.e., dropping), certain
temperatures, or pressures.
Upper Explosive Limit
Also known as Upper Flammable Limit. Is the highest
concentration (expressed in percent of vapor or gas in the air by volume) of a substance that will
burn or explode when an ignition source is present. Theoretically above this limit the mixture is
said to be too "rich" to support combustion. The difference between the LEL and the
UEL constitutes the flammable range or explosive range of a substance. (See also LEL.)
Vapor
The gaseous form of substances which are normally in the liquid or solid
state (at normal room temperature and pressure).
Vapor Density
The weight of a pure vapor or gas compared with the weight of
an equal volume of dry air at the same temperature and pressure. ff the vapor density is less than
one, the material is lighter than air and may rise. If the vapor density is greater than one, the
material is heavier than air and will stay low to the ground.
The pressure exerted by the vapor within the
container against the sides of a container. This pressure is temperature dependent; as the
temperature increases, so does the vapor pressure. The lower the boiling point of a liquid, the
greater vapor pressure at a given temperature.
Water Reactive
SUBSTANCES that react violently when in contact with water.
They can be either be flammable solids or corrosives.
Return to the Chemical Hygiene Plan Index.
