WAC 296-841-300
Definitions.
Breathing zone
The space around and in front of an employee's nose and
mouth, forming a hemisphere with a six to nine inch radius.
Ceiling limit
See Permissible exposure limits (PELs).
Dust
Solid particles suspended in air. Dusts are generated by
handling, drilling, crushing, grinding, rapid impact,
detonation, or decrepitation of organic or inorganic materials
such as rock, ore, metal, coal, wood, grain, etc.
Exposed or exposure
The contact an employee has with a toxic substance,
harmful physical agent or oxygen deficient condition, whether
or not protection is provided by respirators or other personal
protective equipment (PPE). Exposure can occur through
various routes of entry, such as inhalation, ingestion, skin
contact, or skin absorption.
Fume
Solid particles suspended in air, generated by
condensation from the gaseous state, generally after
volatilization from molten metals, etc.
Gas
A normally formless fluid which can be changed to the
liquid or solid state by the effect of increased pressure or
decreased temperature or both.
General exhaust ventilation
The general movement of air out of an area or
permit-required confined space by mechanical or natural means.
Immediately dangerous to life or health (IDLH)
An atmospheric condition that would:
• Cause an immediate threat to life
or
• Cause permanent or delayed adverse health effects
or
• Interfere with an employee's ability to escape
Mist
Liquid droplets suspended in air, generated by
condensation from the gaseous to the liquid state or by
breaking up a liquid into a dispersed state, such as by
splashing, foaming, spraying or atomizing.
Nuisance dust (or inert dust)
Dusts that, when inhaled, have little adverse effect on
the lungs and do not produce significant organic disease or
toxic effect when exposures are kept under reasonable control.
The biological reaction to these dusts in lung tissue has
the following characteristics:
• The architecture of the air spaces remains intact
• Scar tissue (collagen) isn't formed to a significant
extent
• The tissue reaction is potentially reversible
Oxygen deficient
An atmosphere with an oxygen content below 19.5% by
volume.
Permissible exposure limits (PEL)
The amount of an airborne chemical, toxic substance, or
other harmful agent that must not be exceeded during any part
of the workday.
An airborne chemical or toxic substance can have 3 PEL
values:
• TWA8. This is an 8-hour, time-weighted average limit.
• Short-term exposure limit (STEL). This is typically a
15-minute, time-weighted average limit.
• Ceiling limit (C). This is an instantaneous limit.
Short-term exposure limit (STEL)
See Permissible exposure limits (PELs).
Temper
To condition air for a specific work environment by
changing its temperature or moisture content.
Time weighted average (TWA8)
See Permissible exposure limits (PELs).
Toxic substance
Any chemical substance or biological agent, such as
bacteria, virus, and fungus, which is any of the following:
• Listed in the latest edition of the National Institute
for Occupational Safety and Health (NIOSH) Registry of Toxic
Effects of Chemical Substances (RTECS)
• Shows positive evidence of an acute or chronic health
hazard in testing conducted by, or known to, the employer.
• The subject of a material safety data sheet kept by or
known to the employer showing the material may pose a hazard
to human health.
Vapor
The gaseous form of a substance that is normally in the
solid or liquid state.
Ventilation
Providing, circulating or exhausting air into or out of
an area or space.
[Statutory Authority: RCW 49.17.010, 49.17.040, 49.17.050,
49.17.060. 07-05-062, § 296-841-300, filed 2/20/07, effective
4/1/07; 04-18-079, § 296-841-300, filed 8/31/04, effective
11/1/04; 03-20-115, § 296-841-300, filed 10/1/03, effective
1/1/04.]