Confined space

Confined space entry requires a written program that identifies hazards, controls entry, assigns trained roles, and regulates rescue and emergency response. A permit-required confined space is a confined space that contains or could contain a hazardous atmosphere, engulfment hazard, trapping/asphyxiation configuration, or another serious safety or health hazard. Employers must evaluate each space before entry and treat spaces as permit-required until pre-entry procedures demonstrate otherwise. [6] [2] [13]

Hazard assessment and classification should cover both atmospheric and physical hazards before entry begins.

• Identify atmospheric hazards such as oxygen deficiency, oxygen enrichment, flammable gases or vapors, combustible dusts, and toxic contaminants.
• Identify physical hazards such as mechanical, electrical, hydraulic, pneumatic, engulfment, entrapment, temperature extremes, and harmful skin or eye contact hazards.
• Survey the surrounding area for external hazards such as drifting vapors from tanks, piping, or sewers.
• Reevaluate the space whenever conditions, configuration, work scope, or alarm conditions change.

[3] [12] [2] [2] Atmospheric testing is required both to evaluate hazards and to verify acceptable entry conditions. Testing should be done with properly calibrated, direct-reading or otherwise suitable instruments by trained personnel, with results recorded on the permit or kept at the job site. The required testing order is oxygen first, then combustible gases/vapors, then toxic gases/vapors. Where atmospheres may be stratified, sample top, middle, and bottom, and during descent test approximately 4 feet in the direction of travel and to each side. Entrants must be allowed to observe testing and receive the results. [4] [4] [4] [8] [19]

• Acceptable oxygen range for entry is 19.5% to 23.5%. Less than 19.5% is oxygen-deficient; more than 23.5% is oxygen-enriched.
• Flammable gases or vapors must remain below 10% of the lower explosive/lower flammable limit for entry.
• Common toxic screening parameters may include hydrogen sulfide, carbon monoxide, sulfur dioxide, ammonia, aromatic hydrocarbons, and any other contaminants reasonably expected in the space.
• Do not rely on smell or appearance to judge safety; some toxic atmospheres are odorless, and some gases such as hydrogen sulfide can deaden the sense of smell.

[1] [6] [17] Ventilation is a primary control for atmospheric hazards, especially where alternate procedures are used. Mechanical or forced-air ventilation should be used to purge and maintain safe conditions when it can effectively control the hazard, but entry is only allowed after testing confirms acceptable conditions and monitoring shows they are maintained. If hazardous conditions develop or ventilation fails, entrants must evacuate immediately and the space must be reevaluated. Ventilation alone is not enough if non-atmospheric hazards remain or if the atmosphere cannot be kept safe. [15] [14] [10] [5]

Isolation and lockout/tagout are critical before entry. The space must be removed from service and protected against the release of energy or materials by methods such as blanking, blinding, disconnecting or misaligning lines, double block and bleed, lockout/tagout of energy sources, and blocking mechanical linkages. Lines that could introduce flammable, toxic, injurious, or incapacitating substances must be positively isolated, and inadvertent reconnection must be prevented. Spaces should also be emptied, drained, cleaned, washed, flushed, or purged as needed before entry. [6] [11] [1] [12]

A confined space entry permit should be completed before entry into a permit-required confined space and kept at the job site for the duration of the work. The permit should identify the space, purpose of entry, hazards, atmospheric test results, isolation steps, ventilation, communication methods, rescue procedures, required equipment, authorized entrants, attendants, supervisors, and expiration time. If work is interrupted, conditions change, or alarms change, the permit must be reissued or replaced. Entry cannot proceed if required items are incomplete or if prohibited conditions exist. [2] [9] [7] [14]

• Provide at least one trained attendant outside the permit space for the duration of entry operations.
• Designate and train authorized entrants, attendants, entry supervisors, and atmospheric testers/monitors.
• Maintain reliable communication between entrants and the attendant.
• Use continuous or periodic monitoring as necessary to ensure acceptable entry conditions are maintained.
• Terminate entry and evacuate immediately if a prohibited condition develops or monitor alarms activate.

[8] [8] [17] [2] Rescue and emergency response must be planned before entry, not improvised after an incident. The preferred strategy is self-rescue whenever entrants can recognize danger and exit on their own. If self-rescue is not possible, non-entry rescue using retrieval systems is preferred because it can begin immediately without exposing rescuers to the same hazards. Entry rescue should be used only when necessary and must be supported by trained rescuers, respiratory protection where needed, medical response capability, and preplanned information such as number of victims, location, exposure time, suspected cause, atmospheric results, and isolation status. [16] [16] [6] [16]

Personal protective equipment and rescue equipment must match the hazards identified. Depending on the space and task, this may include full-body harnesses with retrieval lines, respiratory protection such as SCBA or supplied air, protective clothing, gloves, eye/face protection, intrinsically safe lighting, non-sparking tools, communication equipment, ladders for ingress/egress, and hoisting or retrieval devices. PPE is a supplement to hazard elimination and control, not a substitute for proper isolation, ventilation, and atmospheric verification. [1] [7] [8]

Key OSHA/Cal/OSHA regulatory principles are consistent: evaluate the space, classify it correctly, isolate hazards, test before entry, monitor during entry as needed, provide attendants and trained roles, use a written permit system for permit spaces, and establish rescue capability before entry. In practice, a compliant confined space entry should not begin until hazards are identified, energy and material sources are isolated, atmospheric testing confirms acceptable conditions, required equipment is in place, the permit is authorized, and emergency arrangements are ready. [8] [13] [18]