Confined Spaces

Chapter 296-809, WAC

Effective Date: 05/01/04

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WAC 296-809-800

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Acceptable entry conditions

The conditions that must exist in a permit-required confined space to allow safe entry and work


An individual stationed outside one or more permit-required confined spaces to monitor the entrants

Blanking or blinding

The absolute closure of a pipe, line, or duct by fastening a solid plate (such as a spectacle blind or a skillet blind) that completely covers the bore. It is capable of withstanding the maximum pressure of the pipe, line, or duct with no leakage beyond the plate.

Confined space

A space that is all of the following:

- Large enough and arranged so an employee could fully enter the space and work.

- Has limited or restricted entry or exit. Examples of spaces with limited or restricted entry are tanks, vessels, silos, storage bins, hoppers, vaults, excavations, and pits.

- Not primarily designed for human occupancy.

Double block and bleed

The closure of a line, duct, or pipe by closing and locking or tagging 2 in-line valves and by opening and locking or tagging a drain or vent valve in the line between the 2 closed valves.


Any occurrence (including any failure of hazard control or monitoring equipment) or event internal or external to the permit-required confined space that could endanger authorized entrants.


The surrounding capture of a person by a liquid or finely divided (flowable) solid substance that can be inhaled 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.

Enter (entry)

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



If the opening is large enough for the worker to fully enter the space, a permit is required even for partial body entry. Permits aren't required for partial body entry where the opening isn't large enough for full entry, although other rules such as chapter 296-803 WAC, Lockout-Tagout, and chapter 296-841 WAC, Airborne contaminants may apply.


An employee who is authorized by the employer to enter a permit-required confined space

Entry permit (permit)

The written or printed document that is provided by you to allow and control entry into a permit-required confined space and that contains the information required in WAC 296-809-500, Permit Entry Procedures.

Entry supervisor

The person (such as the employer, crew leader, or crew chief) responsible for:

- Determining if acceptable entry conditions are present at a permit-required confined space where entry is planned;

- Authorizing entry and overseeing entry operations


- ATerminating entry as required.

Hazardous atmosphere

An atmosphere that may expose employees to the risk of death, incapacitation, impairment of ability to self-rescue (that is, escape unaided from a permit-required confined space), injury, or acute illness caused by one or more of the following:

- Flammable gas, vapor, or mist in excess of 10% of its lower flammable limit (LFL).

- Airborne combustible dust at a concentration that meets or exceeds its LFL.



This concentration may be approximated as a condition in which the dust obscures vision at a distance of 5 feet
(1.52 m) or less.

- Atmospheric oxygen concentration below 19.5% or above 23.5%.

- Atmospheric concentration of any substance which may exceed a permissible exposure limit. For additional information about atmospheric concentration, see chapter 296-62 WAC, Parts F, G, and I, General Occupational Health Standards and chapter 296-841 WAC, Airborne contaminants.



An airborne concentration of a substance that isn't capable of causing death, incapacitation, impairment of ability to self-rescue, injury, or acute illness due to its health effects isn't covered by this definition.

- Any other atmospheric condition that is immediately dangerous to life or health.



You can find guidance on establishing acceptable atmospheric conditions for air contaminants, which have no WISHA-determined doses or permissible exposure limits using other sources of information, such as:

- Material safety data sheets required by WAC 296-800-170, Employer Chemical Hazard Communication.
- Published information
- Internal documen

Hot work permit

A written authorization to perform operations, for example, riveting, welding, cutting, burning, and heating, that can provide a source of ignition.

Immediately dangerous to life or health (IDLH)

Any of the following conditions:

- An immediate or delayed threat to life

- Anything that would cause irreversible adverse health effects

- Anything that would interfere with an individual’s ability to escape unaided from a permit-required confined space.



Some materials hydrogen fluoride gas and cadmium vapor, for example may produce immediate transient effects that, even if severe, may pass without medical attention, but are followed by sudden, possibly fatal collapse 12 to 72 hours after exposure. The victim “feels normal” after recovery from transient effects until collapse. Such materials in hazardous quantities are considered to be “immediately” dangerous to life or health (IDLH).


The displacement of the atmosphere in a permit-required confined space by a noncombustible gas (such as nitrogen) to such an extent that the resulting atmosphere is noncombustible.



This procedure produces an IDLH oxygen-deficient atmosphere.


The process by which a permit-required confined space is removed from service and completely protected against the release of energy and material into the space by such means as:

- Blanking or blinding

- Misaligning or removing sections of lines, pipes, or ducts

- A double block and bleed system

- Lockout or tagout of all sources of energy


- Blocking or disconnecting all mechanical linkages.

Line breaking

The intentional opening of a pipe, line, or duct that is or has been carrying flammable, corrosive, or toxic material, an inert gas, or any fluid at a volume, pressure, or temperature capable of causing injury.

Non-permit confined space

A confined space that does not contain actual hazards or potential hazards capable of causing death or serious physical harm.

Oxygen deficient atmosphere

An atmosphere containing less than 19.5% oxygen by volume

Oxygen enriched atmosphere

An atmosphere containing more than 23.5% oxygen by volume

Permit-required confined space or permit space

A confined space that has one or more of the following characteristics capable of causing death or serious physical harm:

- Contains or has a potential to contain a hazardous atmosphere

- Contains a material with the potential for engulfing someone who enters

- Has an internal configuration that could allow someone entering to be trapped or asphyxiated by inwardly converging walls or by a floor, which slopes downward and tapers to a smaller cross section

- Contains any physical hazard. This includes any recognized health or safety hazards including engulfment in solid or liquid material, electrical shock, or moving parts

- Contains any other recognized serious safety or health hazard that could either:

- Impair the ability to self-rescue
- Result in a situation that presents an immediate danger to life or health.

Permit-required confined space program

An overall program for:

- Controlling and appropriately protecting employees from permit-required confined space hazards;


- Regulating employee entry into permit-required confined spaces.

Prohibited condition

Any condition in a permit-required confined space that isn't allowed by the permit during the authorized entry period.

Rescue service

The personnel designated to rescue employees from permit-required confined spaces.

Retrieval system

The equipment used for non-entry rescue of persons from permit-required confined spaces, such as a retrieval line, full-body harness or wristlets, and a lifting device or anchor.


The process of identifying and evaluating the hazards that entrants may be exposed to in a permit-required confined space. Testing includes specifying the tests that are to be performed in the permit-required confined space.



Testing allows employers to devise and implement adequate controls to protect entrants during entry, and to determine if acceptable entry conditions are present.

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