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Office of Security, Safety and Risk Management

MSDS Terms and Acronyms

  1. Action Level, AL -- Certain OSHA regulations take effect if this exposure level (conc. in air) is reached. These regulations include workplace air analysis, employee training, medical monitoring, and record keeping. This level is about half of the permissible exposure limit.
  2. American Conference of Governmental Industrial Hygienists, ACGIH -- This organization include professionals in government and education involved in occupational safety and health programs. One important function of this group is the determination and publication of recommended occupational exposure limits for chemical substances.
  3. American National Standards Institute, ANSI -- This private organization identifies industrial and public national consensus standards. These standards relate to safe design and performance of equipment and practices
  4. Ceiling, C -- This is the employee's exposure which shall not be exceeded at any time during the workday.
  5. Immediately Dangerous to Life and Health, IDLH -- These values are used to determine the appropriate respirators for hazardous chemicals. These values stand for the maximum concentration from which a worker could escape within 30 minutes without any escape-impairing symptoms or irreversible health effects in the event of a respirator failure.
  6. Lethal Concentration 50, LC-50 -- This concentration of a hazardous material in air is expected to kill 50% of a group of test animals when given as a single respiratory exposure in a specific time period.
  7. Lethal Concentration Low, LC-LO -- This value indicates the lowest concentration of a substance in air that caused death in humans or laboratory animals. The value may represent periods of exposure that are less than 24 hours(acute) or greater than 24 hours (subacute and chronic).
  8. Lethal Dose 50, LD-50 -- The single dose, other than inhalation, that causes death in 50% of an animal population from exposure to a hazardous substance.
  9. Lethal Dose Low, LD-LO --The lowest dose, other than inhalation, that caused death in humans or animals.
  10. Milligrams per Cubic Meter of Air, mg/m^3 -- This unit of measuring concentrations of particulate (minute dust-like particles).
  11. National Fire Protection Association, NFPA -- This group of fire protection personnel established a rating system used on many labels of hazardous materials. The label consist of a diamond divided into four sections. The sections represent the following categories
    1. Health;
    2. Flammability;
    3. Reactivity;
    4. Special precautions.
  12. National Institute of Occupational Safety and Health, NIOSH -- This agency of the Public Health Service test and certifies respiratory and air-sampling devices. It recommends to OSHA exposure limits for hazardous substances. It also investigates incidents and researches occupational safety.
  13. Parts Per Million, ppm -- This is a common unit of concentration of gas or vapor in air expressed with many exposure limits. It is defined as parts of gas or vapor per million parts of air by volume at 25 degrees C and 1 atm of pressure.
  14. Permissible Exposure Limit, PEL -- This is one of the most important OSHA limits used. It is defined as the allowable limit for air contaminant in which workers may be exposed day after day without adverse health effects.
  15. Recommended Exposure Limit, REL -- The highest allowable air concentration that will not injure a person.
  16. Short-Term Exposure Limit, STEL -- The 15-minute time-weighted average exposure which must not be exceeded at any time during a work day.
  17. Synergy -- The combined effects of more than one hazardous material resulting in more damage than the additive effects of each material.
  18. Threshold Limit Value, TLV -- The air concentration levels of hazardous substances to which workers may be repeatedly exposed day after day without adverse health effects.
  19. Threshold Limit Value-Time-Weighted Average, TLV-TWA -- Time-weighted average concentration for an 8-hour workday and a 40-hour work week in which a worker may be repeated exposed without adverse health effects.
  20. Threshold Limit Value-Short-Term Exposure Limit, TLV-STEL -- This is the maximum concentration which workers can be exposed for 15 minutes continuously without adverse health affects. Only four of these 15-minutes exposures are permitted per day and must have 60 minutes between exposures.The TLV-TWA still must not be exceeded.
  21. Threshold Limit Value-Ceiling -- This is a defined boundary unlike TLVs which are guidelines. It is the concentration which should never be exceeded at any time during the working exposure.
  22. Time Weighted Average -- The workers average airborne exposure in any 8-hour work day of a 40 hour work week which should not be exceeded.
  23. Toxic Concentration Low, TC-LO -- This is the lowest concentration of an airborne substance in which humans or animals have been exposed that resulted with any toxic effects in humans or produced any tumors or adverse reproductive effects in animals or humans.
  24. Toxic Dose Low, TD-LO -- The lowest dose of a hazardous substance introduced by means other than inhalation over a given time period that has been reported to produce toxic effects in humans or produced any tumors or adverse reproductive effects in animals or humans.