The following are definitions for Confined Space:

Acceptable entry condition. Condition 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

Attendant. A person designated to remain outside the confined space and monitor conditions for any health or safety impacts and perform the attendant's duties as described on the entry permit (see Confined Space Training)

Authorized entrant. A person who has been determined to be medically and physically capable to perform work in a confined space and has the appropriate training for that entry (see Confined Space Training)

Blanking, blinding, line blank. The absolute closure of a gas or liquid filled line, pipe, or duct by the fastening of a solid plate that completely seals the bore and is capable of withstanding the maximum pressure of the line, pipe, or duct without leaking

Competent entry supervisor. The person who is responsible for determining if acceptable entry conditions are present for entry, for authorizing entry, overseeing entry operations, and terminating any permit-required confined space operations (see Confined Space Training)

Confined space. A space that has all of the following three characteristics:

1. It is large enough and so configured that a person can bodily enter and perform assigned work
2. It has limited or restricted means for entry or exit
3. It is not designed for continuous human occupancy

Confined spaces are divided into two categories based on their inherent hazard potential:

1. Permit-required confined space
2. Non-permit-required confined space

Confined space owner. A person at SLAC, either a building, facility, or area manager or a person designated by such, responsible for monitoring the condition of confined spaces in their areas

Confined space profile. A document that summarizes the facts about a confined space that may have bearing on safe entry, work and egress from that space. The profile will also document any necessary emergency response actions or phone numbers unique to the space. Profiles are stored in the Confined Space Inventory.

Double block and bleed. System for isolating a space by closing two valves on a line leading to a space, and bleeding the line between the valves to create a buffer zone

Emergency. Any occurrence or event internal or external to the confined space that could endanger the entrants, or any condition not permitted on the entry permit. This includes any failure of hazard control, monitoring, communication, or lighting equipment.

Emergency rescue. The procedures by which persons incapable of self-rescue are removed from a confined space

Emergency services. Local fire, police, and ambulance departments who are responsible for emergency response and emergency rescue efforts

Emergency condition. Any confined space situation where any airborne material encountered that is measured or estimated to be at its immediately dangerous to life and health (IDLH) or 10 percent lower flammable limit (LFL) value is considered an emergency condition. No entry will be made and the situation must be mitigated by trained emergency response personnel.

Engulfment. The surrounding and effective capture of a person by a liquid or finely divided (flowable) solid substance that can be inhaled to cause death by filling or plugging of the respiratory system or than can exert enough force on the body to cause death by strangulation, constriction, or crushing

Entry (into a confined space). When any part of a person's body passes through the plane of the opening of the space

Entry permit. The written or printed document that is used to allow and control entry into a permit-required confined space

Hazardous atmosphere, potentially hazardous atmosphere. An atmosphere that has the potential to cause death, incapacitation, impairment of ability for self-rescue, acute illness, delayed illness, or effects that can result in injury.

Hot work. Any work that involves burning, welding, riveting, or similar fire-producing operations, as well as work that produces a source of ignition, such as drilling, abrasive blasting, and space heating

Hot work permit. The written authorization to perform hot work operations

Immediately dangerous to life and health (IDLH). [wh5]Any condition that poses an immediate or delayed threat to life or that would cause irreversible adverse health effects or interfere with an individual's ability to escape unaided from a space. The IDLH also represents a maximum concentration from which, in the event of respirator failure, a person could escape within 30 minutes without experiencing any irreversible health effects.

Inerting. The process of filling a space with an inert non-flammable material for the purpose of displacing or diluting oxygen to remove the flammable potential of the confined space atmosphere

Isolation, isolating. The process by which a confined space is removed from service and completely protected against releasing material into the space. This process includes such means as blanking, double block and bleed, or misalignment of lines, lockout of all energy sources, blocking of energy sources, or removing mechanical linkages.

Line breaking. The process of physically opening a line that contains or previously contained a hazardous material or hazardous pressure. A double-block and bleed is required between the source of hazardous energy and the point where the line is broken.

Non-permit-required confined space (NPRCS). A confined space that does not contain or have the potential to contain any atmospheric or other hazard capable of causing death or physical harm (see permit-required confined space). A non-permit-required confined space may become a permit-required confined space if there are hazardous materials brought into the space or if hazardous activities are conducted in the space.

Oxygen concentration of ambient air. Normal ambient air contains 20.9 percent oxygen by volume

Oxygen deficiency. Any measured oxygen concentration that is less than normal ambient air. For confined space entry purposes, any measured oxygen concentration that is less than 19.5 percent indicates an oxygen deficiency. The cause of this oxygen deficiency must be determined before entry will be allowed and controls on this potential hazard will be put in place before entry is allowed. The oxygen deficiency can be caused by

• An intrusion of an unknown material into the space that has diluted or displaced the available oxygen or
• The presence of something that has consumed the oxygen such as oxidation (rust), chemical reactions (including combustion), absorption (on wet activated carbon), or biological action

Oxygen-deficient atmosphere. An atmosphere that has less than 19.5 percent oxygen by volume. When the oxygen content is below 19.5 percent an air-purifying respirator cannot be worn and a supplied air respirator must be used for entry.

Oxygen enrichment. Any measured oxygen concentration that is greater than normal ambient air (20.9 percent). Any measured concentrations measured greater than 20.9 percent is indicative that there is an oxygen source inside the confined space (leaking welding hose, chemical reaction). Special precautions must be taken to understand and control this hazard potential before space entry is allowed.

Oxygen-rich atmosphere. An oxygen concentration in the space of greater than 23.5 percent oxygen by volume

Permit-required confined space (PRCS). 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 which slopes downward and tapers to a smaller cross-section
• Contains any other recognized serious safety or health hazard

Permit system. The written procedure for obtaining, preparing, issuing and retrieving entry permits for entry into confined spaces and returning the space to service following termination of entry.

Prohibited condition. Any condition in permit-required confined space that is not allowed by the permit during the period when the entry is authorized.

Purging. The method by which gases, vapors, or other airborne hazards are initially displaced, diluted, or removed from a confined space. Purging is the initial step in controlling atmospheric hazards before entry into the confined space. See ventilating.

Rescue service. See emergency services

Retrieval system. System for conducting non-entry rescue of persons from confined spaces. This system includes mechanical retrieval or extraction devices (a rated tripod, davit, or other anchorage plus winch) and full body harness. Wristlets may be used to aid in a difficult extraction; however, wristlets should not be used to support a person's weight.

Testing. The process by which the hazards that may confront entrants of a permit space are identified and evaluated

Two-person rule. Rule that people must work in teams of two in defined situations

Ventilating. The process where clean fresh air is blown into the confined space while persons are in the space (See purging). In some cases, local exhaust ventilation may be required to remove contaminants from the space generated at a point source. An example of this would be the use of local exhaust ventilation to remove fumes and noxious gases if welding were taking place in the confined space.