Environmental, Health and Safety Services

Confined Spaces Definitions

Acceptable entry conditions - The conditions that must exist in a confined space before entering to ensure that employees can safely enter into, and safely work within, the space.

Attendant - A designated individual stationed outside of one or more permit spaces who assesses the status or authorized entrants, and who performs duties as specified by this program.

Barrier - A physical obstruction that blocks or limits access.

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

  • A blank is designed as a flat plate between two flanges, typically inside the flange bolt pattern. The blank must be sized for full design pressure (maximum non-shock presssure rating) of the line.
  • A blind is designed as a bolted flat plate, which can be used to terminate a pipe line.

Competent Person - One who is capable of identifying existing and predictable hazards in the surroundings or working conditions which are unsanitary, hazardous, or dangerous to employees, and who has the authorization to take prompt corrective measures to eliminate them.

Confined space - Any space that is:

  1. Large enough and so configured that an employee can bodily enter it,
  2. Has limited or restricted means for entry or exit, and
  3. Is not designed for continuous employee occupancy.
  • Examples include, but are not limited to: bins, boilers, pits (e.g. elevator, escalator, pump, valve, etc.), manholes (e.g. sewer, storm drain, electrical, communication, or other utility), storage tanks (e.g. fuel, chemical, water, other liquid/solid/gas), incinerators, scrubbers, concrete pier columns, sewers, transformer vaults, heating/ventilation/air-conditioning (HVAC) ducts, storm drains, water mains, precast concrete and other pre-formed manhole units, drilled shafts, enclosed beams, vessels, digesters, lift stations, cesspools, silos, air receivers, sludge gates, air preheaters, step up transformers, turbines, chillers, bag houses, and/or mixers/reactors.

Control - The action taken to reduce the level of any hazard inside a confined space using engineering methods (ex. ventilation), and then using these methods to maintain the reduced hazard level. Personal protective equipment is not a control.

Controlling Contractor - The employer that has overall responsibility for construction at the worksite. Note: If the controlling contractor owns or manages the property, then it is both a controlling employer and a host employer.

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

Early-warning system - The method used to alert authorized entrand and attendants than an engulfment hazard may be developing. Ex. alarms activated by remote sensors, lookouts with equipment for immediately communicating with the entrants and attendants.

Emergency - Any occurrence or event inside or outside of the confined space that could endanger entrants, including any failure of power, hazard control, or monitoring equipment.

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 stangulation, constriction, crushing, or suffocation.

Entrant (Authorized) - An employee authorized by the Entry Supervisor to enter a confined space.

Entry - The action by which any part of a person passes through an operning into a permit-required confined space. Entry inlcudes 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, whether or not such action is intentional or any work activities are actually performed in the space.

Entry Employer - Any employer who decides that an employee it directs will enter a permit space. Note: an employer cannot avoid the duties of the standard merely by refusing to decide whether its employees will enter a permit space, and OSHA will consider the failure to so decide to be an implicit decision to allow employees to enter those space if they are working int he proximity of the space.

Entry Permit - The written or printed document that is provided by the employer who designated the space a permit space to allow and control entry into a permit space and that contains the required information. At Virginia Tech, the Assessment Form serves as a permit if conditions are present that warrant the space being designated as permit-required.

Entry rescue - When a rescue service enters a permit space to rescue one or more employees.

Entry Supervisor - The departmental person responsible for determining if acceptable entry conditions are present in a confined space where entry is planned, for authorizing and overseeing entry operations, and for terminating entry as required by this program.

Ground-fault circuit-interrupter - A device designed to disconnect an electric circuit when it seeks ground through a person or grounded object, thus preventing electric shock and fires.

Hazard - A physical hazard or hazardous atmosphere.

Hazardous Atmosphere - an atmosphere presenting a potential for death, disablement, injury, or acute illness from one or more of the following causes:

  • A flammable gas, vapor or mist in excess of 10% of its lower flammable limit (LFL),
  • An oxygen deficient atmosphere containing less than 19.5% oxygen by volume, or an oxygen-enriched atmosphere containing more than 23.5% oxygen by volume,
  • Airborne combustible dust at a concentration that meets or exceeds its LFL (airborne combustible dust which obscures vision at five feet or less),
  • An atmospheric concentration of any substance for which a dose or a permissible exposure limit is published in Subpart G, Occupational Health and Environmental Control, or in subpart Z, Toxic and Hazardous Substances, which could result in an employee exposure in excess of its dose or permissible exposure limit, and that could cause death, incapacitation, impairment of ability to self-rescue, injury or acute illness,
    • Note: An atmospheric concentraction of any substance that is not capable of causing death, incapacitation, impairment of ability to self-rescue, injury, or acute illness due to its health effects is not covered by this definition.
  • Any other atmospheric condition that is immediately dangerous to life or health (IDLH).
    • Note: For air contaminants for which OSHA has not determined a dose or permissible exposure limit (PEL), other sources of information, such as Safety Data Sheets (SDS), published information, and internal documents can provide guidance in establishing acceptable atmospheric conditions.

Host Employer - The employer that owns or manages the property where the construction work (or confined space entry) is taking place. At Virginia Tech, the General Contractor of capital projects is considered the property owner/manager. For non-capital projects, Virginia Tech remains the property owner/manager. Refer to Virginia Tech's Contractor Safety Program for more information regarding coordination of confined space entry involving contractors and subcontractors.

Hot work permit - The employer's written authorization to perform hotwork operations (e.g. welding, cutting, burning, or 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 that would cause irreversible adverse health effects or that would interfere with an individual's ability to escape unaided from a confined space.

Note: Some materials, such as 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 12-72 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.

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

Note: This procedure produces an IDLH oxygen-deficient atmosphere that can only be entered using self-contained breathing apparatus (SCBA) and following permit-required confined space entry procedures.

Isolation - The process by which an energy source is removed from service and employees are completely protected against the release of energy and material into the space, and contact with a physical hazard, 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; or blocking or disconnecting all mechanical linkages, or placement of barriers to eliminate the potential for employee contact with a physical hazard.

LEL/LFL - Lower Explosive/Flammable Limit; the minimum concentration of vapor-in-air or vapor-in-oxygen below which propagation of flame does not occure on contact with a source of ignition. Expressed in terms of percentage by volume of gas or vapor in air.

Limited or restricted means of egress (i.e. entry or exit) - A condition that has a potential to impede an employee's movement into or out of a confined space. Ex. trip hazards, poor illumination, slippery floors, inclining surfaces, and ladders.

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.

Local exhaust ventilation - A system used during welding, cutting or other similar operations in confined spaces as necessary to remove harmful gases, smoke and fumes.

Lockout-tagout - Placing locks or tags on the energy isolating device (e.g. breaker boxes, control switches, valves, etc.) to prevent the unauthorized reenergization of the device or circuit while work is being performed by personnel. Tags shall indicate that the energy isolated device must not be operated until the tag is removed by the individual(s) that installed the tag.

Monitoring - the process used to identify and evaluate the hazards after an auhorized entrant enters the space. It involves checking for changes periodically or continuously after the completion of the initial testing or evaluation of the space.

Non-entry rescue - When a rescue service, usually the attendant, retrieves employees in a permit space without entering the permit space.

Non-permit confined space - A confined space which does not meet the definition of a permit-required confined space.

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.

PEL - Permissible Exposure Limit; the allowable air contaminant level established by the Occupational Safety and Health Administration (OSHA).

Permit-Required Confined Space (PRCS) - A confined space which after evaluation is found to have one or more of the following characteristics:

  • Contains or has the 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, or
  • Contains any other recognized serious safety or health hazard.

Physical hazard - An existing or potential hazard that can cause death or serious physical damage. Ex. explosives, mechanical, electrical, hydraulic and pneumatic energy, radiation, temperature extremes, engulfment, noise, inwardly converging surfaces, chemicals that can cause deather or serious physical damage through skin or eye contact (rather than through inhalation), etc.

Qualified Person - One who by possession or a recognized degree, certificate, or professional standing, or who by extensive knowledge, training, and experience, has successfully demonstrated his/her ability to solve or resolve problems relating to the subject matter, the work, or the project.

Rescue Team - Those persons whom the employer has designated prior to any permit-required confined space entry to perform rescues from confined spaces. Blacksburg Volunteer Fire Department is the rescue team for Virginia Tech.

Retrieval system - The equipment used for non-entry rescue of persons from confined spaces, and includes retrieval lines, chest or full body harness, and a lifting device or anchor. A retrieval line is primarily for use in vertical entry confined spaces, and must not be used in confined spaces consisting of horizontal tunnels or spaces where obstructions could increase the hazard to the entrant during emergency retrieval.

Serious physical damage - An impairment or illness in which a body part is made funtionally useless, or is substantially reduced in efficiency. It may be permanent or temporary. Ex. loss of consciousness, disorientation, reduction in mental efficiency, etc. Such impairment would usually required treatment by a physician or other licensed health-care provider.

Testing - The process by which the hazards that may confront entrants to a confined space are identified and evaluated. The tests that are to be performed in the permit space must be specified (ex. oxygen, LEL, carbon monoxide, and hydrogen sulfide).

UEL/UFL - Upper explosive/flammable limit; the maximum proportion of vapor or gas in air above which flame propagation does not occur. Expressed in terms of percentage by volume of gas or vapor in air.

Ventilation - Controlling a hazardous atmosphere using continuous forced-air mechanical systems that meet the requirements of OSHA (1926.57).

Zero mechanical state - The mechanical potential energy of all portions of the machine or equipment is set so that the opening of the pipe(s), tube(s), hose(s) or actuation of any valve, lever, or button will not produce a movement which could cause injury.