In this module
Objectives covered: LO 3.12.1, LO 3.12.2. By the end you will be able to:
- Identify permit-required confined spaces and their hazards.
- Describe the entry permit, roles, air testing and rescue.
- Summarise the elements of Process Safety Management (PSM).
12.1 Confined spaces
A confined space is large enough to enter, has limited entry or exit, and is not designed for continuous occupancy: tanks, vessels, silos, pits, manholes, septic tanks. It is a permit-required confined space if it has (or may have) a hazardous atmosphere, engulfment hazard, an inwardly converging shape that can trap, or any other serious hazard.
12.2 Safe entry
- Written programme, and a permit signed by the entry supervisor.
- Isolate and lock out lines, agitators and energy.
- Test the air in this order: oxygen (19.5 to 23.5%), then flammables (below 10% LEL), then toxics (e.g. H₂S, CO below limits). Monitor continuously.
- Ventilate with a blower.
- Roles: entrant, attendant outside at all times, entry supervisor.
- Rescue plan with retrieval equipment (tripod, winch, harness). Never enter to rescue without breathing apparatus.
12.3 Process Safety Management (PSM)
OSHA 1910.119 applies to processes with highly hazardous chemicals above threshold quantities (for example ammonia, chlorine, and over 10,000 lb of flammable liquids or gases). Its 14 elements include: employee participation, process safety information, process hazard analysis (HAZOP and others, revalidated every 5 years), operating procedures, training, contractors, pre-start-up safety review, mechanical integrity, hot work permits, management of change, incident investigation, emergency planning, compliance audits and trade secrets.
- 1910.146: permit-required confined spaces.
- 1910.119: process safety management of highly hazardous chemicals.
- See RiskProBD course RPB-HAC 101 for HAZOP, bow-tie and management of change.
In Bangladesh, workers die nearly every year in septic tanks and underground reservoirs, often several at once as co-workers try to rescue the first. Gas from decaying waste (H₂S and methane) and low oxygen kill within minutes. Fertiliser and LPG plants, which run PSM-style systems, have shown that permits, gas testing and trained rescue teams prevent these deaths.
Learning Check
Answer these two questions to check your understanding. You can try again as many times as you like.