Confined Space

A confined space is large enough for a worker to enter, has limited means of entry or exit, and is not designed for continuous occupancy. A permit-required confined space adds a serious hazard: a hazardous atmosphere, engulfment, an inwardly sloping configuration that can trap a person, or any other serious hazard.

Atmospheres

Normal air is about 20.9 percent oxygen; OSHA treats below 19.5 percent as oxygen-deficient. Rust, decay and inert-gas purging consume or displace oxygen with no smell. Hydrogen sulfide from sewage deadens the sense of smell at high concentrations. Carbon monoxide comes from engines and combustion. Flammable vapour is measured against its lower explosive limit (LEL). A four-gas meter reads all four; tests are taken top, middle and bottom, because gases layer.

The permit system

Before entry: identify and isolate hazards (see Lockout/Tagout), ventilate, test the air, and write the permit naming the entrants, the attendant, the entry supervisor, the hazards, the tests and the rescue service. During entry: the attendant stays outside, keeps count, monitors conditions and never enters. Rescue is by retrieval line and tripod where possible, or by a trained rescue team.

Why rescuers die

The instinct to help is strong. When a worker collapses from bad air, the same air will drop the next person who goes in without a respirator. Training replaces instinct with procedure: call rescue, use the retrieval line, do not enter.

Learning it here

Confined-space entry is taught in Water/Wastewater Operator, Shipbuilding, Welding, Industrial Maintenance and HVAC/R programs, and in OSHA 10 and 30.