A B C D E F G H I J K L M N
Q R S T U V W X Y Z
down or select a link to first letter of the word)
ACGIH - ACGIH stands for American Conference of Governmental
Industrial Hygienists. The ACGIH is an association of occupational health
professional employed by the government and educational institutions. The Threshold
Limit Value (TLV) Committee and Ventilation Committee of the ACGIH publish guidelines
which are used worldwide.
Active Ingredient - An active ingredient is the part of a
product which actually does what the product is designed to do. It is not
necessarily the largest part of the product. For example, an insecticidal spray may
contain less than 1% pyrethrin, the ingredient which actively kills insects. The
remaining ingredients are often called inert ingredients.
Acute - Acute means sudden or brief. Acute can be used to
describe either an exposure or a health effect. An acute exposure is a short-term
exposure. Short-term means lasting for minutes, hours or days. An acute health
effect is an effect that develops either immediately or a short time after an
exposure. (Also see Chronic).
Aerosol - An aerosol is a collection of very small
particle suspended in air. The particles can be liquid (mist) or solid (dust or
fume). The term aerosol is also commonly used for a pressurized container (aerosol
spray) which is designed to release a fine spray of material such as paint.
Inhalation of aerosol is a common route of exposure to many chemicals. As well,
aerosols may be fire hazards.
Temperature - The auto-ignition temperature is the lowest temperature at
which materials begin to burn in air in the absence of a spark or flame. Many
chemicals will decompose (break down) when heated. The auto-ignition temperature is
the temperature at which the chemicals formed by decomposition begin to burn.
Auto-ignition temperatures for a specific material can vary by one-hundred degrees Celsius
or more depending on the test method used. Therefore values listed on the MSDS may
be rough estimates. To avoid the risk of fire or explosion, materials must be stored
and handled at temperatures well below the auto-ignition temperature.
Biohazard Materials - Under the Occupational Safety and
Health Administration, a biohazard means those infective agents presenting a risk of
death, injury or illness to employees. For example, a person exposed to a blood
sample from someone with Hepatitis B may contract the disease.
Boiling Point - The boiling point is the temperature at
which the material changes from a liquid to a gas. Below the boiling point, the
liquid can evaporate to form a vapor. As the material approaches the boiling point,
the change from liquid to vapor is rapid and vapor concentration in the air can be
extremely high. Airborne gases and vapors may pose fire, explosion and health
hazards. Sometimes, the boiling point is given as a range of temperatures.
This is because different ingredients in a mixture can boil at different
temperatures. If the material decomposes (breaks down) without boiling, the
temperature at which it decomposes may be given with the abbreviation, "dec."
Carcinogenicity - A carcinogen is a substance which can cause cancer.
Carcinogenic means able to cause cancer. Carcinogenicity is the ability of a
substance to cause cancer. Under the Controlled Products regulation, materials are
identified as carcinogenic if they are recognized as carcinogens by the American
Conference of Governmental Industrial Hygienist (ACGIH), or the International Agency for
Research on Cancer (IARC). MSDS's from the United Stated also identify carcinogens
recognized by the US National Toxicology Program (NTP). The lists of carcinogens
prepared by these organizations include known human carcinogens and some materials which
cause cancer in animal experiments. Certain chemicals may be listed as suspect or
possible carcinogens if the evidence is limited or so variable that a definite conclusion
cannot be made.
CAS Registry Number - The CAS Registry Number is a number
assigned to a material by the Chemical Abstract Service (CAS) to provide a single unique
identifier. A unique identifier is necessary because the material can have many
different names. For example, the name given to a specific chemical may vary from
one language or country to another. The CAS Registry Number has no significance in
terms of the chemical nature or hazards of the material. The CAS Registry Number can
be used to locate additional information on the material, for example, when searching in
books or chemical data bases.
Ceiling (C) - See Exposure Limits for a general explanation.
Chemical Name - The chemical name is a proper scientific name for the principle or
active ingredient of the product. For example, the chemical name for the herbicide
2,4-D is 2,4-dichlorophenoxyacetic acid. The chemical name can be used to obtain
Chronic - Chronic means long-term or prolonged. It can
describe either an exposure or a health effect. A chronic exposure is a long-term
exposure. Long-term means lasting for months or years. A chronic health
effect is an effect that appears months or years after an exposure. The Controlled
Products Regulations describes technical criteria for identifying materials which cause
chronic health effects. (See also Acute).
Oil/Water Distribution - The coefficient of oil/water distribution, also
called the partition coefficient, abbreviated as P, is the ratio of the solubility of a
chemical in an oil to its solubility in water. The P value is typically represented
as a logarithm of P (log P). It indicates how easily the chemical can be absorbed or
stored in the body. The P value is also used to help determine the effects of the
chemical on the environment.
Combustible - Combustible means able to burn.
Broadly speaking, a material is combustible if it can catch fire and burn. (See Combustible Liquid). The terms
combustible and flammable both describe the ability of material to burn. Commonly,
combustible materials are less easily ignited than flammable materials.
Combustible Liquid - Under 29 CFR 1910.106(a)(18), a
combustible liquid has a flash point at or above 37.8?C. This flash point is well
above normal room temperature. Combustible liquids are, therefore, less of a fire
hazard than flammable liquids. If there is a possibility that a combustible liquid
will be heated to a temperature near its flash point, appropriate precautions must be
taken to prevent a fire.
Compressed Gas - Under 29 CFR 1910.1200(c), a compressed
gas is a gas or mixture of gases having, in a container, an absolute pressure exceeding 40
psi at 70?F (21.1?C); a gas or mixture of gases having, in a container, an absolute
pressure exceeding 104 psi at 130?F (54.4?C) regardless of the pressure at 70?F; or, a
liquid having a vapor pressure exceeding 40 psi at 100?F (37.8?C) as determined by ASTM
D-323-72. Regardless of whether a compressed gas is packaged in an aerosol can, a
pressurized cylinder or a refrigerated container, it must be stored and handled very
carefully. Puncturing or damaging the container or allowing the container to become
hot may result in an explosion.
Corrosive Material - A corrosive material can attack
(corrode) metals or human tissue such as the skin or eyes. Corrosive material can
cause metal containers or structural to become weak and eventually to leak or
collapse. Corrosive materials can burn or destroy human tissues on contact and can
cause effects such as permanent scarring or blindness.
- A dangerously reactive material that can react vigorously:
with water to produce a very toxic gas;
on its own by polymerization or decomposition; or
under conditions of shock, or an increase in pressure or temperature.
dangerously reactive material may cause a fire, explosion or other hazardous
condition. It is very important to know which conditions (such as shock, heating or
contact with water) may set off a dangerous reaction so that appropriate preventative
measures can be taken.
- The density of a material is its mass for a given volume. Density is usually given
in units of grams per milliliter (g/ml) or grams per cubic centimeters (g/cc).
Density is closely related to specific gravity (relative density). The volume of a
material in a container can be calculated from its density and mass.
Embryotoxicity - An embryo is an organism in its early stages of development
prior to birth. In humans, the embryo is the developing child from conception to the
end of the second month of pregnancy. (See also Fetus).
Embryotoxic means harmful to the embryo. Embryotoxicity is the ability of a
substance to cause harm to the embryo. (See also Fetotoxicity and Reproductive
Rate - The evaporation rate is a measure of how quickly the material becomes a vapor
at normal room temperature. Usually, the evaporation rate is given in caparison to
certain chemicals, such as butyl acetate, which evaporates fairly quickly. For
example, the rate might be given as "0.5 grams of material evaporates during the same
time that 1 gram of butyl acetate evaporates. Often, the evaporation rate is
given only as greater or less than 1, which means the material evaporates faster or slower
than the comparison chemical. In general, a hazardous material with a higher
evaporation rate presents a greater hazard than a similar compound with a lower
* LEL, LFL - The Lower Explosive Limit
(LEL), or lower flammable limit (LFL), is the lowest concentration of gas or vapor which
will burn or explode if ignited.
UEL, UFL - The Upper Explosive Limit (UEL),
or the upper flammable limit (UFL), is the highest concentration of gas or vapor which
will burn or explode if ignited.
From the LEL to the UEL, the mixture is explosive. Below the LEL, the mixture is too
lean to burn. Above the UEL, the mixture is too rich to burn. However,
concentrations above the UEL are still very dangerous because, if the concentration is
lowered (for example, by introducing fresh air), it will enter the explosive range.
In reality, explosive limits for a material vary since they depend on many factors such as
air temperature. Therefore the values given on an MSDS are approximate.
Too Lean to Burn
Can Burn Explosively
Too Rich to Burn
Percent volume of vapor or gas in air
explosive limits are usually given as the percent by volume of the material in the
air. One percent by volume is 10,000 ppm. For example, gasoline has a LEL of
1.4% and a UEL of 7.6%. This means that gasoline vapors at concentrations of 1.4% to
7.6% (14,000 to 76000 ppm) are flammable or explosive.
Exposure Limits - An exposure limit is the concentration of
a chemical in the workplace to which most people can be exposed without experiencing
harmful effects. Exposure limits should not be taken as sharp dividing lines between
safe and unsafe exposures. It is possible for a chemical to cause health effects, in
some people, at concentrations lower than the exposure limits. Exposure limits have
different names and different meaning depending on who developed them and whether or not
they are legal limits.
Limit Values (TLV's) are exposure guidelines developed by
the American Conference of Governmental Industrial Hygienists (ACGIH). They have
been adopted by several governments as their legal limits.
Permissible Exposure Limits (PEL's) are
legal exposure limits in the United States. Sometimes, a manufacturer will recommend
an exposure limit for a material. Exposure limits have not been set for many
chemicals, for many different reasons. For example, there may not be enough
information available to set an exposure limit. Therefore, the absence of an
exposure limit does not necessarily mean the material is not harmful.
are three types of exposure limits in common use:
- Time-Weighted Average exposure limit is the average concentration of
a chemical in air for a normal 8-hour workday and 40-hour workweek to which nearly all
workers may be exposed day after day without harmful effects. Time-weighted average
means that the average concentration has been calculated using the duration of exposure to
different concentrations of the chemical during a specific time period. In this way,
higher and lower exposures are averaged over the day or week.
Short-Term Exposure Limit is the average concentration to which workers can be exposed to
for a short period (usually 15 minutes) without experiencing irritation, long-term or
irreversible tissue damage or reduced alertness. The number of times the
concentration reaches the STEL and the amount of time between these occurrences can also
Ceiling (C) - Ceiling (C) exposure limit is the
concentration which should not be exceeded at any time.
"SKIN" notation (SKIN) means that contact
with the skin, eyes and moist tissues (for example, the mouth) can contribute to the
overall exposure. The purpose of this notation is to suggest that measures be used
to prevent absorption occurs through the skin, then the airborne exposure limits are not
- Fetotoxic means the substance is harmful to the fetus. Fetotoxicity
describes the ability of a substance to harm the fetus. (See also Embryotoxicity, Teratogenicity, and Reproductive Effects).
A fetus is an organism in the later stages of development prior to birth. In human,
it is the unborn child from the end of the second month of pregnancy to birth.
Flammability - Flammable means able to ignite
and burn readily. Flammability is the ability of a material to ignite and burn
readily. (See Combustible, Flammable
Aerosol, Flammable Gas, Flammable Liquid,
Flammable Solid, and Reactive Flammable Material). Local, state and national fire
codes also classify and regulate the use of flammable materials in the workplace.
Aerosol - Flammable Aerosol means an aerosol that, when
tested by the method described in 16 CFR 1500.45, yields a flame projection exceeding 18
inches at full valve opening, or a flash back at any degree of valve opening (29 CFR
1910.1200(c)). A flammable aerosol is hazardous because it may form a torch
(explosive ignition of the spray) or because a fire fuelled by the flammable aerosol may
Gas - A flammable gas is a gas which can ignite readily and burn rapidly or
explosively. Under 29 CFR 1910.1200(c), it is a gas that, at ambient temperature and
pressure, forms a flammable mixture with air at a concentration of thirteen (13) percent
by volume or less; or, a gas that at ambient temperature and pressure forms a range of
flammable mixtures with air wider than twelve (12) percent by volume, regardless of the
lower limit. Flammable gases can be extremely hazardous in the workplace; for
* If the gas accumulates so that its lower explosive limit (LEL)
is reached and if there is a source of ignition, an explosion will occur.
* If there is inadequate ventilation, flammable gases can travel
considerable distances to a source of ignition and flash back to the source of the gas.
Flammable Limits - See Explosive Limits.
Liquids - A flammable liquid gives off a vapor which can be easily ignited at normal
working temperatures. Under the 29 CFR 1910.106(a)(19), a flammable liquid is a
liquid with a flash point (using a closed cup test) below 37.8?C (100F). Flammable
liquids can be extremely hazardous in the workplace; for example:
* If there is inadequate ventilation, flammable gases can travel considerable
distances to a source of ignition and flash back to the flammable liquid.
* It may be difficult to extinguish a burning flammable liquid with
water because water may not be able to cool the liquid below its flash point.
Solid - A flammable solid is a solid material that is liable to cause fire through
friction, absorption of moisture, spontaneous chemical change, or retained heat from
manufacturing or processing or which can ignite readily and when ignited burns vigorously
and persistently as to create a serious hazard (29 CFR 1910.1200(c)). Flammable
solids in the form of dust or powder may be particularly hazardous because they may
explode if ignited.
Back - Flash back occurs when a trail of flammable gas, vapor or aerosol is ignited by
a distant spark, flame or other source of ignition. The flame then travels back
along the trail of gas, vapor or aerosol to its source. A serious fire or explosion
Flash Point - The Flash Point is the lowest temperature at
which a liquid or a solid gives off enough vapor to form flammable air-vapor mixture near
its surface. The lower the flash point, the greater the fire hazard. The flash
point is an approximate value and should not be taken as a sharp dividing line between
safe and hazardous conditions. The flash point is determined by a variety of test
methods which give different results. Two of these methods are abbreviated as OC
(open cup) and CC (closed cup).
Point - The temperature at which a material freezes. (See also Melting Point).
- Impervious Fumes are very small, airborne, solid particles formed by the cooling of a
hot vapor. For example, a hot zinc vapor may form when zinc-coated steel is
welded. The vapor then condenses to form fine zinc fumes as soon as it contacts the
cool surrounding air. Fumes are smaller than dusts and are more easily breathed into
Hazardous - Hazard is the potential for harmful
effects. Hazardous means potentially harmful. The hazards of a material are
evaluated by examining the properties of the material, toxicity, flammability and chemical
reactivity, as well as how the material is used. How a material is used can vary
greatly from workplace to workplace and, therefore, so can the hazard.
- Hazard Combustion Products are chemicals which may be form products when a
material burns. These chemicals may be toxic, flammable or have other hazards.
The chemicals released and their amounts vary depending upon conditions such as the
temperature and the amount of air (or more specifically, oxygen) available. The
combustion chemicals may be quite different from those formed by heating the same material
during processing (thermal decomposition products). It is important to know which
chemicals are formed during combustion in order to plan the response to a fire involving
- Hazardous Decomposition Products are formed when a material decomposes
(breaks down) because it is unstable or reacts with common materials such as water or
oxygen (in air). This information should be considered when planning storage and
IARC - IARC stands for International Agency for Research on
Cancer. IARC evaluates information on carcinogenicity of chemicals, groups of
chemicals and chemicals associated with certain industrial processes. IARC has
published lists of chemicals which are generally recognized as human carcinogens, probable
human carcinogens or carcinogens in animal tests.
IDLH - IDLH stands for Immediately Dangerous to Life or
Health. For the purpose of respirator selection, NIOSH defines the IDLH
concentration as the maximum concentration which would not cause any escape-impairing
symptoms or irreversible health effects to a person exposed for thirty minutes, if the
Impervious - Impervious is a term used to describe protective gloves and
other protective clothing. If a material is impervious to a chemical, then that
chemical cannot readily penetrate through the material or damage the material.
Different materials are impervious (resistant) to different chemicals. No single
material is impervious to all chemicals. If an MSDS recommends wearing impervious
gloves, you need to know the type of material from which the gloves should be made.
For example, neoprene gloves are impervious to butyl alcohol but not the ethyl alcohol.
Incompatible Materials - Incompatible materials can
react with the product or with components of the product and may:
* destroy the structure or function of a
* cause a fire, explosion or violent reaction;
* cause the release of hazardous chemicals.
Ingredient - An inert ingredient is anything other than the active ingredient of a
product. It may be a solvent, colorant, filter or dispersing agent. In some
cases, inert ingredients may be hazardous.
- Ingestion means taking a material into the body by mouth (swallowing).
Inhalation - Inhalation means taking a material into the body by breathing it in.
Irritation - Irritancy is the ability of a
material to irritate the skin, eyes, nose, throat, or any other part of the body that it
contacts. Signs and symptoms of irritation include tearing in the eyes and
reddening, swelling, itching and pain or the affected part of the body. Irritancy is
often described as mild, moderate or severe, depending on the degree of irritation caused
by a specific amount of the material. Irritancy may also be described by a number on
a scale of 0 to 4, where 0 indicated no irritation and 4 means severe irritation.
Irritancy is usually determined in animal experiments. The Controlled Products
Regulations, describe technical criteria for identifying materials which are skin or eye
LC50 - LC stands for lethal concentration. LC50 is the
concentration of material in the air which causes the death of 50% (one half) of a group
of test animals. The material is inhaled over a set period of time, usually 1 to 4
hours. The LC50 helps determine the short-term poisoning potential of a
material. (See also LD50). The MSDS must indicate the species of animal tested
and the route by which the hazardous substance was administered. Note: if the LC50
is known for a mixture, this should be listed for the mixture and not the separate
LD50 - LD stands for lethal dose. LD50 is the amount of a
material, given all at once, which causes death of 50% (one half) of a group of test
animals. The LD50 can be determined by any route of entry, but dermal (applied to
skin) and oral (given by mouth) are the most common. The LD50 is one measure of the
short-term poisoning potential of a material. (See also LC50). The MSDS must
indicate the species of animal tested and the route by which the hazardous substance was
administered. Note: if the LD50 is known for a mixture, this should be listed for
the mixture and not the separate ingredients.
Explosion(ive) Limit (LEL) - See Explosive Limits.
Flammable Limit (LFL) - See Explosive Limits.
Point - The melting point is the temperature at which a solid material
becomes a liquid. The freezing point is the temperature at which a liquid material
becomes a solid. Usually one value or the other is given on an MSDS. It is
important to know the melting or freezing point for storage or handling purposes.
For example, a melted or frozen material may burst a container. As well, a change of
physical state could alter the hazards of the material.
- The abbreviation mg/m3 stands for milligrams (mg) of material per cubic meter (m3) of
air. It is a unit of metric measurement for concentration (mass/volume). The
concentration of any airborne chemical can be measured in mg/m3, whether it is a solid,
liquid, gas or vapor.
- A mist is a collection of liquid droplets suspended in air. A mist can be formed
when spraying or splashing a liquid. It can also be formed when a vapor condenses
into liquid droplets in the air. (See also Aerosol).
Mutagenicity - A mutagen is a substance which can cause changes in the DNA of cells
(mutations). Mutagenic means able to cause mutations. Mutagenicity is the
ability of a substance to cause mutations. A number of mutagenicity tests are used
to screen chemicals for possible carcinogenicity or reproductive effects. This is
because there is some evidence that mutations can increase the Risk of cancer and
reproductive problems such as infertility or birth defects. However, mutagenicity
test results are not very reliable predictors of these effects. One reason for this
is that the human body can repair mutations while most mutagenicity tests cannot.
Mutagenicity is indicated on MSDS's because it is an early indicator of potential hazard,
and often there is very little evidence available on possible carcinogenic or reproductive
effects. The Controlled Products Regulations describe technical criteria for
identifying materials which are mutagenic.
Number - See UN Number.
NIOSH - NIOSH stands for National Institute for Occupational
Safety and Health. NIOSH is a branch of the Department of Health and Human Services
which undertakes research and develops occupational health and safety standards.
- NTP stands for National Toxicology Program. This program is part of the
Department of Health and Human Services. The NTP has a large program for testing
the potential carcinogenicity of chemicals. It also does many other types of
studies on short-term and long-term health effects.
Nuisance Particulate - Nuisance particle is a term used by the ACGIH to
describe airborne materials (solids and liquids) which have little harmful effects on the
lungs and do not produce significant disease or harmful effects when exposures are kept
under reasonable control. Nuisance particulates may also be called nuisance dusts.
High levels of nuisance particulates may reduce visibility and can get into the
eyes, ears and nose.
Threshold - The Odor Threshold is the lowest concentration, in ppm, of a chemical in
the air that is detectable by smell. The odor threshold should only be regarded as
an estimate. This is because odor thresholds are commonly determined under
controlled laboratory conditions using people trained in odor recognition. As well,
in the workplace, the ability to detect the odor of a chemical varies form person to
person and depends on conditions such as the presence of other odorous materials.
Odors cannot be used as a warning of unsafe conditions since workers may become used to
the smell (adaptation), or the chemical may numb the sense of smell, a process called
olfactory fatigue. However, if the odor threshold for a chemical is well below its
exposure limit, odor can be used to warn of a problem with your respirator.
- OECD stands for Organization for Economic Cooperation and Development. The OECD is
an international agency which supports programs designed to facilitate trade and
development. The OECD has published Guidelines for Testing Chemicals. These
guidelines contain recommended procedures for testing chemicals for toxic and
environmental effects and for determining physical and chemical properties.
- OEL stands for Occupational Exposure Limit. (See Exposure Limit for a general explanation).
OSHA - OSHA stands for Occupational Safety and Health
Administration. It is the branch of the US government which sets and enforces
occupational health and safety regulations. For example, OSHA sets the legal
exposure limits in the United States, which are called Permissible Exposure Limits
(PEL's). OSHA also specifies what information must be given on labels and Material
Safety Data Sheets (MSDS) for materials in the US that have been classified are hazardous
using their criteria.
Oxidizing Material - An oxidizing agent or material gives up oxygen easily or
can readily oxidize other materials. Examples of oxidizing agents are chlorine and
peroxide compounds. These chemicals will support a fire and are highly reactive.
Coefficient - See Coefficient of Oil/Water Distribution.
PEL - PEL stands for Permissible Exposure Limit. PEL's are legal
limits in the United States set by the Occupational Safety and Health Administration
(OSHA). (See Exposure Limits for
a general explanation).
Personal Protective Equipment (PPE) - Personal Protective
Equipment (PPE) is clothing or devices worn to help isolate a person from direct exposure
to a hazardous material or situation. On a MSDS, personal protective equipment which
protects from chemical exposure is listed. This can include protective clothing,
respiratory protection and eye protection. The use of protective equipment is the
least preferred method of protection from hazardous exposures. It can be unreliable
and, it if fails, the person can be left completely unprotected. This is why
engineering controls are preferred. Sometimes, personal protective equipment may be
needed along with engineering controls. For example, a ventilation system (an
engineering control) reduces the inhalation hazard of a chemical, while gloves and labcoat
(personal protective equipment) reduce skin contact. In addition, personal
protective equipment can be an important means of protection when engineering controls are
not practical; for example, during an emergency or other temporary conditions such as
- The pH is a measure of the acidity or basicity (alkalinity) of a material when dissolved
in water. It is expressed on a scale from 0 to 14. Roughly, pH can be divided
into the following ranges:
pH 0 - 2 Strongly acidic
pH 3 - 5 Weakly acidic
pH 6 - 8 Neutral
pH 9 - 11 Weakly basic
pH 12 - 14 Strongly basic
- The abbreviation stands for parts per million. It is a common unit of
concentration of gases or vapor in air. For example, 1 ppm of a gas means that 1
unit of gas is present for every 1 million units of air.
Density - See Specific Gravity.
Reproductive Toxicity - Reproductive effects are problems in the reproductive
process which may be caused by a substance. Possible reproductive effects include
reduced fertility in the male or female, menstrual changes, miscarriage, embryotoxicity,
fetotoxicity, teratogenicity, or harmful effects to the nursing infant form chemicals in
breast milk. Most chemicals can cause reproductive effects if there is an extremely
high exposure. In these cases, the exposed person would experience other noticeable
signs and symptoms caused by the exposure. These signs and symptoms act as a warning
of toxicity. Chemicals which cause reproductive effects in the absence of other
significant harmful effects are regarded as true reproductive hazards. Very few
workplace chemicals are known to be true reproductive hazards. The Controlled
Products Regulations describe technical criteria for identifying materials which have
reproductive toxicity. These criteria refer to adverse effects on fertility.
- Sensitization is the development, over time, of an allergic reaction to a
chemical. The chemical may cause a mild response on the first few exposures but, as
the allergy develops, the response becomes worse with subsequent exposures.
Eventually, even short exposures to low concentration can cause very severe
reaction. There are two different types of occupational sensitization: skin and
respiratory. Typical symptoms of skin sensitivity are swelling, redness, itching ,
pain and blistering. Sensitization of the respiratory system may result in symptoms
similar to a severe asthma attack. These symptoms include wheezing, difficulty in
breathing, chest tightness, coughing and shortness of breath.
Notation - See Exposure Limits for
a general explanation.
Gravity - Specific Gravity is the ratio of the density of a material to the density of
water. The density of water is about 1 gram per cubic centimeter (g/cc).
Materials which are lighter than water (specific gravity less than 1.0) will float.
Most materials have specific gravities exceeding 1.0, which means they are heavier than
water and will sink. Knowing the specific gravity is important for planning spill
clean-up and fire fighting procedures. For example, a light flammable liquid such as
gasoline may spread and if ignited burn on top of a water surface.
- Stability is the ability of a material to remain unchanged in the presence of heat,
moisture or air. An unstable material may decompose, polymerize, burn or explode
under normal environmental conditions. Any indication that the material is unstable
gives warning that special handling and storage precautions may be necessary.
- STEL stands for Short-Term Exposure Limit. (See Exposure Limits for a general
Synergistic - As used on MSDS, synergism means that exposure to more than one
chemical can result in health effects greater than when expected when the effects of
exposure to each chemical are added together. Very simply, it is like saying 1 + 1 =
3. When chemicals are synergistic, the potential hazards of the chemicals should be
reevaluated, taking their synergistic properties into consideration.
- Synonyms are other names for the same chemical. For example, methanol and methyl
hydrate are synonyms for methyl alcohol. Synonyms may help in locating additional
information on a chemical.
- The transportation of potentially hazardous materials is regulated under the HM-181
regulations which are administered by the Department of Transportation (DOT). These
regulations set out criteria for the classification of materials as dangerous goods and
state how these materials must be packaged and shipped.
Teratogenicity - A teratogen is a substance which can cause birth defects.
Teratogenic means able to cause birth defects. Teratogenicity is the ability of a
chemical to cause birth defects. Teratogenicity results from a harmful effect to the
embryo or fetus. (See also Reproductive
Decomposition Products - Thermal Decomposition Products are chemicals which may be
formed when the material is heated but does not burn. These chemicals may be toxic,
flammable, or have other hazards. The chemicals released and their amounts vary
depending upon conditions such as temperature. The thermal decomposition products
may be quite different from the chemicals formed by burning the same material (hazardous
combustion products). It is important to know which chemicals are formed by thermal
decomposition because this information is used to plan ventilation requirements for
processes where a material may be heated.
TLV - TLV stands for Threshold Limit Value. It is the
occupational exposure limit established by the American Conference of Governmental
Industrial Hygienist (ACGIH). TLV is a registered trademark of ACGIH. (See Exposure Limits for a general
Toxicity - Toxic mean able to cause harmful health effects. Toxicity is the
ability of a substance to cause harmful health effects. Description of toxicity
(e.g., low, moderate, severe, etc.) depend on the amount needed to cause an effect or the
severity of the effect.
Name - A trade name is the name under which a product is commercially known.
Some materials are sold under common names, such as Stoddard solvent or degreaser, or
internationally recognized trade name, like Varsol. Trade names are sometimes
identified by symbols such as 'TM' for an 'R' with a circle around it.
- TWA stands for Timed-Weighted Average. (See Exposure Limits for a general
Number - UN Number stands for United Nations number. The UN number is a
four-digit number assigned to potentially hazardous material (such as gasoline, UN 1203)
or class of material (such as corrosive liquids, UN 1760). These numbers are used by
fire fighters and other emergency response personnel for identification of material during
transportation emergencies. UN numbers are internationally recognized. NA
(North America) numbers are used only for shipments with Canada and the United
States. UN, NA and PIN numbers have the same use.
Explosion(ive) Limit (UEL) -
See Explosion Limits.
Flammable Limit - See Explosion Limits
- A Vapor is the gaseous form of a material which is normally solid or liquid at
room temperature and pressure. Evaporation is the process by which a liquid is
changed into a vapor. Sublimation is the process by which a solid is changed
directly into the vapor state.
Density - Vapor Density is the mass per unit volume of a pure gas or vapor. On
an MSDS, the vapor density is commonly given as a ration of the density of the gas or
vapor to the density of air. The density of air is given a value of 1. Light
gases (density less than 1) such as helium rise in air. If there is inadequate
ventilation, heavy gases and vapors (density greater than 1) can accumulate in low lying
areas such as pits and along floors.
Pressure - Vapor Pressure is the pressure of a vapor when in equilibrium with
its liquid or solid form. It is a measure of the tendency of a material to form a
vapor. The higher the vapor pressure, the higher the potential vapor
concentration. In general, a material with a high vapor pressure is more likely to
be an inhalation or fire hazard than a similar material with a lower vapor pressure.