Glossary of Terms: O

Occupational exposure limit (OEL)
The 8 hour OEL is the time-weighted average concentration for a normal 8 hour day or 40 hour working week to which most workers may be repeatedly exposed, day after day, without adverse effect.
Occupational Illness
A harmful condition or sickness that results from exposure in the workplace to a biological, chemical, or physical agent or an ergonomic hazard. See ergonomics.
Occupational safety
The maintenance of a work environment that is relatively free from actual or potential hazards that can injure employees.
Occupational Safety and Health Administration (OSHA)
The United States governmental agency that establishes and enforces safety standards in the workplace.
Octave Band(s)
A frequency band whose upper band edge frequency is twice the lower band frequency. a. 1/1 octave (whole octave) In sound pressure measurement, the audio spectrum is divided into adjacent frequency bands called octaves, where the center frequency of each octave band is twice the center frequency of the octave band directly below it. There are eleven octave bands in the audio spectrum, as pictured in the following diagram.
OLtime, %OL, OL%
Sound level meter measurements. OLtime is the period of time during which the input signal is above the linear measurement range of the instrument. OL% is the fraction of run time during which an overload condition exists.
Open path
Infrared gas detection with transmitter and receiver devices located at a distance apart.
OSHA
US Occupational Safety and Health Administration, US Department of Labor.
Overload (OL)
An overload will occur whenever the input signal exceeds the dynamic range of the instrument.
Oxidizing agent
(aka Oxidizer) A substance that gives up oxygen easily (this oxygen can fuel a fire) or reduces the hydrogen in other compounds. Some examples of oxidizing agents are peroxides, chlorates, perchlorates, nitrates and permanganates. Oxidation and reduction reactions always occur at the same time. Presence of an oxidizer increases the fire hazard. See reducing agent.
Oxygen deficiency
That concentration of oxygen by volume below which atmosphere supplying respiratory protection must be provided. It exists in atmospheres where the percentage of oxygen by volume is less than 19.5 percent oxygen.
Oxygen-enriched atmosphere
An atmosphere containing more than 23.5 percent oxygen by volume.
Oz
Ounce (weight).