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Chemical Hygiene Plan - Section 5

Glossary of Terms



The American Conference of Governmental Industrial Hygienists is a voluntary membership organization of professional industrial hygiene personnel in governmental or educational institutions. The ACGIH develops and publishes recommended occupational exposure limits each year called Threshold Limit Values (TLV's) for hundreds of chemicals, physical agents, and biological exposure indices.
Short duration, rapidly changing conditions.
Acute Exposure
An intense exposure over a relatively short period of time.
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 chemical (gas or vapor) that can cause death or unconsciousness by suffocation. Simple asphyxiants, such as nitrogen, either remove 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.

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Boiling Point
The temperature at which the vapor pressure of a liquid equals atmospheric pressure or at which the liquid changes to a vapor. The boiling point is usually expressed in degrees Celsius. If a flammable material has a low boiling point, it indicates a special fire hazard.

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Degrees Celsius; the common metric laboratory temperature scale.
"C" or Ceiling
A description usually seen in connection with ACGIH exposure limits. It refers to the concentration that should not be exceeded, even for an instant. It may be written as TLV-C or Threshold Limit Value-Ceiling. (See also Threshold Limit Value).
A substance or physical agent that may cause cancer in animals or humans.
CAS Number
Identifies a particular chemical by the Chemical Abstracts Service, a service of the American Chemical Society that indexes and compiles abstracts of worldwide chemical literature called Chemical Abstracts.
cc or CC
Cubic centimeter, a volumetric measurement that is also equal to one milliliter (ml).
As broadly applied to the chemical industry, an element or a compound produced by chemical reactions on a large scale for either direct industrial and consumer use or for reaction with other chemicals.
Chemical Reaction
A change in the arrangement of atoms or molecules to yield substances of different composition and properties. (see Reactivity)
Persistent, prolonged or repeated conditions.
Chronic Exposure
A prolonged exposure occurring over a period of days, weeks, or years.
According to the DOT and NFPA, combustible liquids are those having a flash point at or above 100°F (37.8°C), or liquids that will burn. They do not ignite as easily as flammable liquids. However, combustible liquids can be ignited under certain circumstances, and must be handled with caution. Substances such as wood, paper, etc., are termed "Ordinary Combustibles".
The relative amount of a material in combination with another material. For example, 5 parts of (acetone) per million (parts of air).
A substance that according to the DOT, causes visible destruction or permanent changes in human skin tissue at the site of contact or is highly corrosive to steel or aluminum.
Cubic Meter (m3)
A measure of volume in the metric system.
Pertaining to or affecting the skin.

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The breakdown of a chemical or substance into different parts or simpler compounds. Decomposition can occur due to heat, chemical reaction, decay, etc.
Pertaining to or affecting the skin.
An inflammation of the skin.
Dilution Ventilation
See General Ventilation.
The United States Department of Transportation is the federal agency that regulates the labeling and transportation of hazardous materials.
Shortness of breath; difficult or labored breathing.

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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).
The study of disease in human populations.
Reddening of the skin.
Evaporation Rate
The rate at which a material is converted to vapor (evaporates) at a given temperature and pressure when compared to the evaporation rate of a given substance. Health and fire hazard evaluations of materials involve consideration of evaporation rates as one aspect of the evaluation.

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Degrees Fahrenheit; the common temperature scale used in the U.S.
Flammable Liquid
According to the DOT and NFPA a flammable liquid is one that has a flash point below 100°F. (See Flash Point)


Classes Of Flammable Liquids:
Flammable Solvent Class Boiling Point Flash Point
Class 1A <100°F (38°C) <73°F (23°C)
Class 1B ³100°F (38°C) <73°F (23°C)
Class 1C ³100°F (38°C) Between 73°F and 100°F
Flash Point
The lowest temperature at which a liquid gives off enough vapor to form an ignitable mixture with air and burn when a source of ignition (sparks, open flames, cigarettes, etc.) is present. Two tests are used to determine the flash point: open cup and closed cup. The test method is indicated on the MSDS after the flash point.

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General Ventilation
Also known as general exhaust ventilation, this is a system of ventilation consisting of either natural or mechanically induced fresh air movements to mix with and dilute contaminants in the workroom air. This is not the recommended type of ventilation to control contaminants that are highly toxic, when there may be corrosion problems from the contaminant, when the worker is close to where the contaminant is being generated, and where fire or explosion hazards are generated close to sources of ignition (See Local Exhaust Ventilation).
See Grams per Kilogram.
Gram (g)
A metric unit of weight. One ounce equals 28.4 grams.
Grams per Kilogram (g/Kg)
This indicates the dose of a substance given to test animals in toxicity studies. For example, a dose may be 2 grams (of substance) per kilogram of body weight (of the experimental animal).

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Hazardous Material
Any substance or compound that has the capability of producing adverse effects on the health and safety of humans.

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A solid, liquid or compressed gas that has a flash point of less than 140 °F. Ignitable material may be regulated by the EPA as a hazardous waste.
The term applied to two substances to indicate that one material cannot be mixed with the other without the possibility of a dangerous reaction.
Taking a substance into the body through the mouth, such as food, drink, medicine, or unknowingly as in contaminated hands or cigarettes, etc.
Breathing in of an airborne substance that may be in the form of gases, fumes, mists, vapors, dusts, or aerosols.
A substance that is added to another to prevent or slow down an unwanted reaction or change.
A substance that produces an irritating effect when it contacts skin, eyes, nose, or respiratory system.

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See Kilogram.
Kilogram (kg)
A unit of weight in the metric system equal to 2.2 pounds.

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See Liter.
See Lethal Concentration -50%.
See Lethal Dose -50%
See Loser Explosive Limit.
Lethal Concentration 50
The concentration of an air contaminant (LC) 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 (LD-50) that will kill 50 percent of the test animals in a group within the first 30 days following exposure.
See Lower Explosive Limit
Liter (L)
A measure of volume. One quart equals 0.9 liters.
Local Exhaust Ventilation (Also known as Exhaust Ventilation)
A ventilation system that captures and removes the contaminants at the point where they are being produced before they escape into the workroom air. The system consists of hoods, ducts, a fan and possibly an air-cleaning device. Advantages of local exhaust ventilation over general ventilation include: It removes the contaminant rather than dilutes it, it requires less air flow and thus is more economical over the long term; and the system can be used to conserve or reclaim valuable materials. However, the system must be properly designed with correctly shaped and placed hoods, and correctly sized fans and ductwork.
Lower Explosive Limit (LEL) (Also known as Lower Flammable Limit)
The lowest concentration of a substance that will produce a fire 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 LFL, the air/contaminant mixture is theoretically too "lean" to burn. (See also UEL).

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M3 or m3
See Cubic Meter.
Melting Point
The temperature at which a solid changes to a liquid. A melting range may be given for some substances or mixtures
See Milligram
See Milligrams per Kilogram.
See Milligrams per Cubic Meter.
Milligram (mg)
A unit of mass in the metric system. One thousand milligrams equal one gram.
Milligrams per Cubic Meter
Units used to measure air (mg/m3) concentrations of dusts, gases, mists, and fumes.
Milligrams per Kilogram
This indicates the dose of a substance (mg/kg) given to test animals in toxicity studies. For example, a dose may be 2 milligrams (of substance) per kilogram of body weight (of the experimental animal).
Milliliter (ml or mL)
A metric unit used to measure volume. One milliliter equals one cubic centimeter. One thousand milliliters equal one liter.
See Milliliter.
The Mine Safety and Health Administration; a federal agency that regulates the mining industry in the safety and health area.
Anything that can cause a change (mutation) in the genetic material of a living cell.

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Stupor or unconsciousness caused by exposure to a chemical.
The National Fire Protection Association is a voluntary membership organization whose aims are to promote and improve fire protection and prevention. NFPA has published 16 volumes of codes known as the National Fire Codes. Within these codes is Standard No. 704, Identification of the Fire Hazards of Materials. This is a system that rates the hazard of a material during a fire. These hazards are divided into health, flammability, and reactivity hazards and appear in a well- known diamond system using from zero through four to indicate severity of the hazard. Zero indicates no special hazard and four indicates severe hazard.
The National Institute of 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 tests and certifies respirators for workplace use.

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Odor Threshold
The minimum concentrations of a substance at which a majority of test subjects can detect and identify the substance's characteristic odor.
Having to do with the mouth.
The Occupational Safety and Health Administration - a federal agency under the Department of Labor that publishes and enforces safety and health regulations for most businesses and industries in the United States.
The process of combining oxygen with some other substance or a chemical change in which an atom loses electrons.
Is a substance that gives up oxygen easily to stimulate combustion of organic material.
Oxygen Deficiency
An atmosphere having less than the normal percentage of oxygen found in normal air. Normal air contains 21% oxygen.

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See Permissible Exposure Limit.
Permissible Exposure Limit (PEL)
An exposure limit that is published and enforced by OSHA as a legal standard. PEL may be a time-weighted-average (TWA) exposure limit (8-hour), a 15-minute short-term exposure limit (STEL), or a ceiling (C).The PEL's are found in Tables Z-1, Z-2, or Z-3 of OSHA regulations 1910.1000. (See also TLV).
Personal Protective Equipment
Any device or clothing worn by the worker to protect against hazards in the environment. Examples are respirators, gloves, and chemical splash goggles or other appropriate eyewear.
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 a polymerization reaction with an uncontrolled release of energy.
Parts (of vapor or gas) per million (parts of air) by volume. May also pertain to solutions.

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A substance's susceptibility to undergoing a chemical reaction or change that may result in dangerous side effects, such as explosions, burning, and corrosive or toxic emissions. The conditions that cause the reaction, such as heat, other chemicals, and shock, will usually be specified as "Conditions to Avoid" when a chemical's reactivity is discussed on a MSDS.
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.

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A substance that may cause no reaction in a person during initial exposures, but afterwards, further exposures of even small amounts will cause an allergic response to the substance.
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. Also the daily TLV-TWA must not be exceeded.
This designation sometimes appears alongside a TLV or PEL. It refers to the possibility of absorption of the particular chemical though 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.
Short Term Exposure Limit.
Any chemical entity.
Another name by which the same chemical may be known.
Spread throughout the body; affecting many or all body systems or organs; not localized in one spot or area.

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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 represent conditions under which it is believed that nearly all workers may be exposed day after day with no adverse effect. TLV's 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
The average time, over a given work period (e.g. 8-hour workday), of a person's exposure to a chemical or an agent. The average is determined by sampling for the contaminant throughout the time period. Represented as TLV-TWA.
See Threshold Limit Value.
The potential for 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.
See Time Weighted Average.

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See Upper Explosive Limit.
See Upper Explosive Limit and Upper Flammable 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. That is, if the LEL is 12% and the UEL is 35%, then the explosive range of the chemical is 12% to 35%. (See also LEL).

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The gaseous form of substances which are normally in the liquid or solid state (at normal room temperature and pressure).Vapors evaporate into the air from liquids such as solvents. Solvents with low boiling points will evaporate readily.
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Last Updated: 2/10/14