Confined-Space Entry Prep — Drain / Purge / Gas-Test Sequence

Before anyone climbs inside a tank, five things must happen in order: empty it, flush out the fumes, blow in fresh air, test the air with a meter, and keep testing. Skip or shuffle one step and the air inside can still be deadly even though the tank "looks" ready.

Confined spaces kill quietly — bad air has no color and often no smell — and they kill rescuers too. This is one of the most consistently fatal situations in industry.

1. Drain the contents completely.
2. Purge/displace hydrocarbons (inert), THEN ventilate to breathable air — in that order.
3. Gas-test O₂ (~19.5–23.5%), flammables (below LEL), and toxics with a calibrated multi-gas meter.
4. Monitor continuously during entry; one reading is never enough.
5. Hold entry until ALL gates pass, with attendant and rescue provisions in place.

1,030 US workers died in confined-space incidents 2011–2018 (~129/yr; annual range 88–166) (BLS CFOI fact sheet) ; 126 of those were single-episode harmful-substance inhalations, most commonly H₂S (38), CO (23), methane (10) (BLS) .

Valero Delaware City (2005): a contractor and his would-be rescuer died in a nitrogen-purged reactor — entry deaths come from un-verified atmospheres and impulsive rescue, not absent paperwork (CSB) .