API TES cheat sheet

A confined space entry permit is valid only for the specific tank, task, and time window named on it; conditions changing outside that scope void the permit.

Atmospheric testing order is oxygen first, then flammables (LEL), then toxics (e.g., H2S); each result must be recorded with time and instrument ID.

Acceptable entry atmosphere: oxygen 19.5-23.5% by volume; flammable gas/vapor below 10% LEL; toxics below the applicable exposure limit.

The attendant (hole watch) remains outside the tank at the entry point at all times during occupancy and never enters to rescue.

Entry supervisor verifies permit conditions, isolation, and atmospheric results before authorizing entry, and cancels the permit when the job ends or conditions change.

Rescue plan must be in place before entry: trained rescuers, retrieval equipment, and summoning method; non-entry retrieval is preferred.

Continuous or periodic atmospheric monitoring is required when conditions can change (residue, sludge disturbance, adjacent operations); intermittent testing alone is insufficient.

Communication between entrant and attendant is maintained continuously; loss of contact triggers evacuation of the entrant.

Isolation for entry includes blanking/blinding or double block-and-bleed of all lines, plus lockout/tagout of mixers and other energy sources.

Tank cleaning sequence: isolate, drain, purge/ventilate, test atmosphere, then enter; cleaning must not begin inside until the atmosphere passes.

Mechanical ventilation is used to maintain a safe atmosphere; pure oxygen must never be used for ventilation or purging.

Sludge and scale can release trapped hydrocarbons or H2S when disturbed, so testing is repeated after agitation or cleaning begins.

Lifelines and retrieval systems are rigged before entry so a non-breathing entrant can be removed without a rescuer entering.

Intrinsically safe or appropriately rated lighting and tools are used; voltage and equipment class must suit the flammable atmosphere.

Water washing and steam cleaning of tanks that contained flammables require bonding/grounding considerations and control of static and hot surfaces.

Entrants wear PPE specified by the hazard assessment (e.g., chemical-resistant clothing, respiratory protection, harness); respirators do not substitute for ventilation.

A standby rescue team and equipment are staged when non-entry retrieval is not feasible; the attendant never performs entry rescue alone.