OSHA Glossary Terms

A quick reference guide.

Acute

Acute effects appear shortly after exposure, usually one to three days, while chronic effects take longer to appear, sometimes months or years.

Attendant

The individual stationed outside a permit space to perform attendant duties. The attendant’s major function is to monitor and protect the authorized entrants.

Broad Range Sensors

Sensors that only indicate that a hazardous threshold of a class of chemicals has been reached.

Ceiling Limit

An airborne concentration of a toxic substance in the work environment, which should not be exceeded. If instantaneous monitoring is not feasible, then the ceiling is a 15 minute time-weighted average exposure not to be exceeded at any time during the working day.

Chemical Asphyxiants

A special category of toxin. They render the body incapable of using an adequate supply of oxygen.

Confined Space

A space that: Is large enough and so configured that an employee can bodily enter and perform assigned work; and has limited or restricted means for entry or exit (for example, tanks, vaults and pits are spaces that may have limited means of entry); and is not designed for continuous employee occupancy.

Confined Space Entry

The action by which a person passes through an opening into a permit-required confined space. Entry includes ensuing work activities in that space and is considered to have occurred as soon as any part of the entrant’s body breaks the plane of an opening into the space.

Eight-Hour Weighted Average

The eight-hour weighted average (TWA) refers to concentrations of airborne toxic materials that have been averaged over an eight-hour working day.

Engulfment

The surrounding and effective capture of a person by a liquid or finely divided (flowable) solid substance that can be aspirated to cause death by filling or plugging the respiratory system or that can exert enough force on the body to cause death by strangulation, constriction, or crushing.

EFI

Electromagnetic interference.

Field Calibration

Verifying whether an instrument is functioning properly and giving the correct readout within the limits specified by the manufacturer of the span (calibration or cal) gas.

Function Check

A function check, or bump test, means using simple tests (such as exposing sensors to calibration gas or exhaling into the oxygen sensor) to show that the instrument will respond to the chemical(s) of concern and that all alarms operate as they were designed.

IDLH

Immediately dangerous to life or health (IDLH) is any condition that poses an immediate or delayed threat to life or that would cause irreversible adverse health effects or that would interfere with an individual’s ability to escape unaided from a permit space.

Inerting

The displacement of the atmosphere in a permit space by a noncombustible gas (such as nitrogen) to such an extent that the resulting atmosphere is noncombustible. Note: Produces an IDLH oxygen-deficient atmosphere.

LEL

The lower explosive limit, LEL, is the minimum concentration of vapor or gas in air below which propagation of flame does not occur on contact with a source of ignition. Below the LEL there is too little combustible fuel to sustain a flammable mixture.

LFL

The lower flammable limit, LFL, is the minimum concentration of vapor or gas in air below which propagation of flame does not occur on contact with a source of ignition. Below the LFL there is too little combustible fuel to sustain a flammable mixture.

PELs

Permissible exposure limits (PELs) are regulatory limits on the amount or concentration of a substance in the air. They may also contain a skin designation. PELs are enforceable.

Permit-Required Confined Space

Permit-required confined space (permit space) is a confined space that has one or more of the following characteristics:

  • Contains or has a potential to contain a hazardous atmosphere.
  • Contains a material that has the potential for engulfing an entrant.
  • Has an internal configuration such that an entrant could be trapped or asphyxiated by inwardly converging walls or by a floor which slopes downward and tapers to a smaller cross-section.
  • Contains any other recognized serious safety or health hazard.

Potential Exposure

When the possibility exists that an employee could be exposed to a hazard because of work patterns, past circumstances, or anticipated work requirements, and it is reasonably predictable that employee exposure could occur at some time during the entry.

RFI

Radio frequency interference.

TWA

The eight-hour time-weighted average (TWA) refers to concentrations of airborne toxic materials that have been averaged over an eight-hour working day.

Upper Explosive Limit

Upper explosive limit (UEL) is the maximum concentration of vapor or gas in air above which propagation of flame does not occur on contact with a source of ignition. Above the UEL there is too little oxygen to sustain a flammable mixture.