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June 01, 2010
Safety 101: Glossary of Workplace Safety Terms R - Z

This glossary contains terms you may run across on this site or in some other safety context. Not included are very common words, words that usually have their ordinary dictionary meaning, and words that are topics on the site.

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RCRA—Resource Conservation and Recovery Act. 

RTECS—Registry of Toxic Effects of Chemical Substances.  This NIOSH publication is one of the information sources OSHA recommends for hazard determination.  RTECS provides data on toxicity for over 50,000 different chemicals.  It has an extensive cross reference listing trade names and synonyms.  It is available as hard copy, computer tape, microfiche, and on-line through the National Library of Medicine.

Reactive (OSHA)—“...means a chemical which in the pure state, or as produced or transported, will vigorously polymerize, decompose, condense, or will become self-reactive under conditions of shocks, pressure or temperature.”  Considered a physical hazard under the law.  ALSO SEE:  POLYMERIZATION, DECOMPOSITION, PHYSICAL HAZARD.

Reactivity—A measure of the tendency of a substance to undergo chemical reaction with the release of energy.

Reducing agent—A chemical which absorbs oxygen in a chemical reaction.

Registry of Toxic Effects of Chemical Substances—SEE RTECS.

Reproductive toxins (29 CFR 1910.1200, Appendix A)—Chemicals that have adverse effects on sexual function and fertility in adult males and females and/or adverse effects on development of offspring.  Examples of reproductive toxins include lead and DBCP.

Respirator use—Respirators are commonly used to protect workers from hazardous vapors and gases and particulates. There are respirators that remove hazards and those which supply the worker with air.  Each type has limitations and advantages.  Proper selection and use is essential to worker health.  OSHA and ANSI provide guidance for respirator use.

Respiratory sensitizer (29 CFR 1910.1200, Appendix A)—“A chemical that will lead to hypersensitivity of the airways following inhalation of the chemical.”

Right to Know law—This is a term applied to a variety of laws and regulations enacted by municipal, county and state governments that provides for the availability of information on chemical hazards.  This also includes the OSHA Hazard Communication Standard.  The different laws that have been enacted around the country vary greatly from the OSHA Standard.  Some require that information be made available not only to employees, but to emergency personnel and the community as a whole.  Many of the local and state laws require submission of work area surveys as well as annual activity reports.  The basic intent of these laws is the same as the OSHA Standard.  ALSO SEE:  HAZARD COMMUNICATION.

SIC Codes—Standard Industrial Classification Codes. OSHA has transitioned to the use of the newer 6-digit NAICS Codes for industry identification, but several OSHA data sets are still available with 4-digit SIC-based data. ALSO SEE: NAICS CODES.

SDS (OSHA)—“means written or printed material concerning a hazardous chemical that is prepared in accordance with paragraph (g) of” OSHA’s Hazard Communication Standard at 29 CFR 1910.1200. Safety data sheets have a specified 16-section format that chemical manufacturers, importers, and other employers responsible for preparing SDSs must follow as of June 1, 2015.

STEL—Short Term Exposure Limit.  This is a term used by the ACGIH to denote “a 15-minute time-weighted average exposure which should not be exceeded at any time during a work day even if the eight hour time-weighted average is within the TLV.”  As with the TWA-TLV, the STEL is only a recommendation.  ALSO SEE:  TLV, TWA.

Safety data sheet (OSHA)—SEE SDS.

Self-reactive chemicals (29 CFR 1910.1200, Appendix B)—“Thermally unstable liquid or solid chemicals liable to undergo a strongly exothermic decomposition even without participation of oxygen (air).”

Short Term Exposure Limit—SEE STEL.

Signal word (OSHA)—“means a word used to indicate the relative level of severity of hazard and alert the reader to a potential hazard on the label.” The signal words used in OSHA’s Hazard Communication Standard at 29 CFR 1910.1200 are “danger” and “warning.” “Danger” is used for the more severe hazards, and “warning” is used for the less severe. ALSO SEE: LABEL, LABEL ELEMENTS.

Signs, placards, process sheets, batch tickets, operating procedures, or other such written materials—These types of methods may be used in lieu of labels on stationary process containers as long as the required information and accessibility is present.

Simple asphyxiant (OSHA)—“means a substance or mixture that displaces oxygen in the ambient atmosphere, and can thus cause oxygen deprivation in those who are exposed, leading to unconsciousness and death.” Simple asphyxiants are considered hazardous chemicals under OSHA’s Hazard Communication Standard at 29 CFR 1910.1200. ALSO SEE: HAZARDOUS CHEMICAL.

Skin notation—The ACGIH TLV Booklet includes the “skin” notation with those listed substances where the overall exposure to a chemical may be increased by the skin route of entry.

Skin sensitizer (29 CFR 1910.1200, Appendix A)—“A chemical that will lead to an allergic reaction following skin contact.”

Solid, flammable—SEE FLAMMABLE SOLID.

Solubility—A measure of the amount of the substance that will dissolve in a given amount of water or other substance.  Solubility data may be given in ppm or percent.

Specific chemical identity (OSHA)—“...means the chemical name, Chemical Abstracts Service (CAS) Registry Number, or any other information that reveals the precise chemical designation of the substance.  ALSO SEE:  CAS.

Specific gravity—The specific gravity is the comparison of densities between two different substances.  Normally, the density of a substance is compared to the density of water, which is one.  ALSO SEE:  DENSITY.

Spontaneous heating—An increase in the internal temperature of a substance due to a chemical or physical change without the application of external heat.

Stability—A measure of the ability of a substance to be handled and stored without undergoing unwanted chemical changes.

Substance (OSHA)—“means chemical elements and their compounds in the natural state or obtained by any production process, including any additive necessary to preserve the stability of the product and any impurities deriving from the process used, but excluding any solvent which may be separated without affecting the stability of the substance or changing its composition.” This definition refers to OSHA’s Hazard Communication Standard at 29 CFR 1910.1200.

TLV—Threshold Limit Value.  The TLVs are a group of recommended concentrations established by the ACGIH for worker protection.  They are based on toxicity data generated from human and animal studies and industrial experience.  TLVs are only recommendations to industry, whereas OSHA enforces the PELs.  ALSO SEE:  TWA, Ceiling, STEL, Skin notation, PEL, ACGIH.

TSCA—Toxic Substances Control Act. TSCA provides for the evaluation of chemical substances before they are used in the workplace.

TWA—Time-weighted average.  This type of Threshold Limit Value established by the ACGIH is “the time-weighted average concentration for a normal 8-hour day and 40-hour workweek, to which nearly all workers may be repeatedly exposed, day after day, without adverse effect.” ALSO SEE:  TLV, ACGIH.

Target organ toxicity—Non-lethal effects on a particular organ arising from exposure to a chemical. These effects can occur after a single exposure (Target organ toxicity – single exposure) or after repeated or prolonged exposure (Target organ toxicity – repeated exposure).  ALSO SEE:  HEPATOTOXINS, NEPHROTOXINS, NEUROTOXINS, BLOOD AGENTS, LUNG AGENTS, REPRODUCTIVE TOXINS, CUTANEOUS HAZARDS, EYE HAZARDS.

Teratogen—A substance which causes birth defects as a result of exposure during fetal development.  ALSO SEE:  REPRODUCTIVE TOXINS.

Threshold Limit Value—SEE TLV.

Toxicity—The measure of the adverse effect exerted on the human body by a poisonous material.

Trade secret (OSHA)—“...means any confidential formula, pattern, process, device, information, or compilation of information that is used in an employer’s business, and that gives the employer an opportunity to obtain an advantage over competitors who do not know or use it.”  Trade secret information is required to be divulged under certain circumstances as defined in section (i) of the Hazard Communication Standard.  Circumstances include medical emergencies, and for occupational health evaluations.


UFL—The highest concentration of a combustible or flammable gas or vapor in air that will produce a flash of fire.  Mixtures above this concentration are too rich to burn.  The UFL of toluene is 7.1%.  ALSO SEE:  LFL, FLAMMABLE LIMITS.


Vapor density—This is the comparison of the density of a vapor or gas to the density of air (air = 1).  A vapor density of less than 1 means it is lighter than air, and greater than 1 means it is heavier than air.  Toluene has a vapor density of 3.14.

Vapor pressure—A measure of the volatility of a liquid, usually given in millimeters of mercury (mmHg).  The vapor pressure of toluene at 68°F is 22 mmHg and 760 mmHg at 231°F (the boiling point).  ALSO SEE:  VOLATILITY.

Volatility—A measure relating the tendency of a liquid to change to a vapor at a specific temperature.  ALSO SEE:  EVAPORATION RATE.

Water-reactive (OSHA)—“...means a chemical that reacts with water to release a gas that is either flammable or presents a health hazard.”  ALSO SEE:  PHYSICAL HAZARD.

Workplace (OSHA)—“...means an establishment, job site, or project, at one geographical location containing one or more work areas.”

Safety Glossary Terms A through C
Safety Glossary Terms D through H
Safety Glossary Terms I through Q

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