Tanks and Vessels

Tanks and vessels on construction and process sites are classified as confined spaces under the 1997 Regulations.
They may have contained flammable liquids, toxic chemicals, or biological material that leaves residual hazards.
Oxygen levels inside tanks can be depleted by rusting, biological activity, or displacement by inert gases.
Access into tanks is often through small manholes, limiting movement and complicating emergency rescue.
Atmospheric testing for oxygen, flammable gases, and toxic substances must precede every entry.
A permit to enter, rescue plan, and standby person are mandatory before anyone enters a tank.
Welding, grinding, or painting inside tanks amplifies fume and fire hazards in the enclosed volume.
Sludge and residues at the bottom of tanks can release toxic gases when disturbed.
Static charges can build up in empty tanks during cleaning, creating ignition risk for flammable vapours.
Multiple fatalities have occurred when workers entered tanks without following confined space procedures.

Toxic atmosphere	Residual chemicals and oxygen depletion inside tanks can cause unconsciousness and death within a single breath.
Rescue difficulty	Restricted access through small manholes makes casualty extraction extremely difficult and time-consuming.
Legal requirement	The Confined Spaces Regulations 1997 impose strict duties for risk assessment, safe systems, and emergency arrangements.

Do

Don't

Treat every tank and vessel as a confined space until proven otherwise
Obtain a confined space entry permit before anyone enters the tank
Test the atmosphere for oxygen, flammable gases, and toxics before and during entry
Ensure a trained standby person is stationed at the entry point throughout
Isolate all feeds, drains, and connections to prevent unexpected inflow
Ventilate the tank continuously using forced mechanical ventilation
Have a rescue plan and trained rescue team ready before entry begins
Clean and purge the tank of residues before internal work commences
Use intrinsically safe lighting and equipment inside potentially flammable tanks
Brief all entrants on the specific hazards, emergency signals, and exit procedures

DON'T enter any tank without a valid confined space permit in place
DON'T rely on a single atmospheric test — monitor continuously during entry
DON'T assume the tank is safe because it was cleaned or drained previously
DON'T leave the standby person's position unattended for any reason
DON'T use non-intrinsically safe electrical equipment in tanks with flammable residues
DON'T disturb sludge or residues without reassessing the atmospheric conditions
DON'T weld or grind inside a tank without additional hot works controls and ventilation
DON'T enter to rescue a casualty without breathing apparatus and a trained team
DON'T forget to isolate all pipework connections — even capped valves can leak
DON'T re-enter after an alarm without retesting the atmosphere and getting clearance

See also: Confined Space Entry Procedures | Atmospheric Monitoring and Gas Testing

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