Welcome to the SAMTRAC Blog

Essential confined space terms and definitions

[fa icon="calendar"] 1/13/18 5:30 PM / by SAMTRAC


Cover image 13 January 2018.jpg

At the end of last year we covered a range of topics related to confined space entry. Today, we’ve compiled a list of the common terms and definitions for this area of occupational health and safety.


Acceptable entry conditions

The conditions that must exist in a permit space to allow entry, and to ensure that employees involved with a permit-required confined space entry can safely enter into – and work within – the space.



An individual stationed outside one or more permit spaces, who monitors the authorised entrants, and who performs all attendant's duties assigned in the employer's permit space programme.


Authorised entrant

An employee who is authorised by the employer to enter a permit space.


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), which completely covers the bore and 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 large enough and configured to allow an employee to enter bodily and perform their assigned work; and
  • has limited or restricted means for entry or exit (for example, tanks, vessels, silos, storage bins, hoppers, vaults and pits are spaces that may have limited means of entry.); and
  • is not designed for continuous employee occupancy.


Double block and bleed

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



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



The surrounding and effective capture of a person by a liquid or finely divided (flowable) solid substance, which can be aspirated (breathed in) and leads to 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.



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.


Entry permit (permit)

The written or printed document that is provided by the employer to allow and control entry into a permit space.


Entry supervisor

The person (such as the employer, foreman or crew chief) responsible for determining if acceptable entry conditions are present at a permit space where entry is planned; for authorising entry and overseeing entry operations, and for terminating entry as required by this section.


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 space), injury or acute illness.


Hot work permit

The employer's written authorisation to perform operations (for example, riveting, welding, cutting, burning and heating) capable of providing a source of ignition.


Immediately dangerous to life or health (IDLH)

Any condition that poses an immediate or delayed threat to life, or will cause irreversible adverse health effects, or that will interfere with an individual's ability to escape unaided from a permit space.



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



The process by which a permit 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 tag-out of all sources of energy; or
  • 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 or, with respect to atmospheric hazards, does not have the potential to contain any hazard capable of causing death or serious physical harm.


Oxygen-deficient atmosphere

An atmosphere containing less than 19.5 per cent oxygen by volume.


Oxygen-enriched atmosphere

An atmosphere containing more than 23.5 per cent oxygen by volume.


Permit-required confined space (permit space)

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 that slopes downward and tapers to a smaller cross-section
  • Contains any other recognised serious safety or health hazard


Permit-required confined space programme (permit space programme)

The employer’s overall programme for controlling, and, where appropriate, for protecting employees from, permit space hazards and for regulating employee entry into permit spaces.


Permit system

The employer's written procedure for preparing and issuing permits for entry and for returning the permit space to service following termination of entry.


Prohibited condition

Any condition in a permit space that is not allowed by the permit during the period when entry is authorised.


Rescue service

The personnel designated to rescue employees from permit spaces.


Retrieval system

The equipment (including a retrieval line, chest or full-body harness, wristlets, if appropriate and a lifting device or anchor) used for non-entry rescue of persons from permit spaces.



The process by which the hazards that may confront entrants of a permit space are identified and evaluated. Testing includes specifying the tests that are to be performed in the permit space.


10 cardinal rules for health and safety training






Topics: Confined spaces, Terms and definitions



SAMTRAC International is the leading occupational health, safety and environment (HSE) management e-learning training course that provides students with the foundational and fundamental knowledge critical to occupational HSE management.

Subscribe to our blog
Download the SAMTRAC Mining glossary

Lists by Topic

see all