What counts as a confined space and how is entry controlled?

Confined space entry is the activity where the consequence of getting it wrong is highest and where the hazard is invisible.

Most of the fatalities in confined spaces are people who entered to help somebody already inside, which is why the standby and rescue arrangements are as important as the entry itself.

What qualifies

Not a question of size. A confined space is an enclosed or partially enclosed area, not intended as a workplace, where there is a risk of an unsafe atmosphere, engulfment or restricted entry and exit.

On the sites we work on, that includes:

**Stormwater and sewer pits,** which is the most common one, and it comes up on almost every drainage job.

**Water and rainwater tanks,** including the tanks on public buildings described in [rainwater tanks and reuse on public sites](/answers/rainwater-tanks-and-reuse-on-public-sites).

**Pump stations and valve chambers.**

**Under-floor voids** in older buildings, where access is restricted and the atmosphere is unknown.

**Some roof and ceiling spaces,** depending on access and ventilation.

**Grease traps and interceptors,** which are the worst case on atmosphere.

A space that is only tight is not automatically a confined space. A space that is tight and may have an unsafe atmosphere is.

The permit

Entry runs under a written permit, issued for that space and that shift, and it covers:

**Atmospheric testing** before entry, for oxygen, flammable gas and toxic gas, with continuous monitoring during the work rather than a single reading at the start.

**Isolation** of anything that could introduce a hazard, including pipework, pumps and electrical supply, locked and tagged out.

**Ventilation,** mechanical where required to maintain a safe atmosphere.

**A standby person** outside the space at all times, in communication with the person inside, who does not enter under any circumstances.

**Rescue arrangements** established before entry, which means equipment on site and people trained to use it, not a phone call.

**Trained and competent entrants,** with the training current.

The permit is closed out when the work finishes and the space is secured.

Hot work inside a confined space

The combination that requires both permits and the strictest controls, because the atmosphere can change during the work and because the ignition source is inside the space.

Which is handled with continuous monitoring, forced ventilation and a fire watch, as set out in [hot works permits and fire watch](/answers/hot-works-permits-and-fire-watch).

The occupied site dimension

A pit in a playground or a tank in a public park adds a second problem: an open space with a person in it, in an area where students or the public are present.

So the opening is barricaded with hard barriers rather than tape, covered when unattended, and controlled by somebody whose job is the barrier rather than the work. The general controls are in [what safety controls are used when working around students or the public](/answers/what-safety-controls-are-used-when-working-around-students-or-the-publ).

Entries are also programmed so an open pit is not left over a lunch break or overnight.

Subcontractors

Most confined space entries on our projects are carried out by specialist subcontractors, which does not transfer the obligation.

The permit system, the verification of training and equipment, and the control of the site remain with the principal contractor, which is the arrangement described in [how subcontractors are engaged and managed](/answers/how-subcontractors-are-engaged-and-managed).

Our capability