Confined space

The definition in the model work health and safety regulations is a four part test, and every part has to be satisfied. A confined space is a space that is enclosed or partially enclosed, is not designed or intended primarily for human occupancy, is at normal atmospheric pressure while anyone is inside it, and involves a risk to health and safety from a harmful atmosphere, from oxygen that is too low or too high, or from engulfment by a stored substance.

The last limb is the one people miss. A space is not a confined space merely because it is tight, dark or awkward to get out of. The hazard has to be atmospheric or related to engulfment.

On a construction site the spaces that usually qualify include pits and sumps, wet wells and sewer chambers, tanks and vessels, some service risers and ducts, silos, pipework large enough to enter, and plant rooms that have been sealed up.

Spaces commonly assumed to be confined spaces that usually are not include trenches and excavations, which have their own extensive controls, and ordinary roof and ceiling voids. Either can become a confined space if an atmospheric hazard is introduced, for example where a trench cuts into contaminated ground or a damaged gas service, or where work in a void generates fumes.

Getting the classification right in both directions matters. Calling everything a confined space devalues the permit system, and missing a genuine one kills people.

For a deeper look, read Permits to Work: The Control That Sits Above the SWMS.

Under the model regulations a person conducting a business or undertaking must not allow or direct a worker to enter a confined space to carry out work unless an entry permit has been issued for that work.

The permit is specific rather than a blanket authorisation. It applies to one confined space, and a permit has to be issued for each entry.

It must identify the confined space it relates to, name the people permitted to enter, state the period during which the work will be carried out, set out the measures to control the risks associated with the proposed work, and include space to acknowledge that the work is complete and that everyone has left the space.

That final field does the real safety work and is the one most often left blank. The sign off closing a permit is how a site knows that nobody is still inside.

Victoria regulates confined spaces under its own Occupational Health and Safety Regulations and also requires an entry permit, and Western Australia has its own work health and safety regulations. The structure is similar across the jurisdictions, but check the local instrument rather than assuming the model wording applies word for word.

A permit records decisions that have already been made. The work behind it follows the hierarchy of controls, and the first question is always whether entry can be avoided at all.

Eliminate the entry. Remote inspection cameras, cleaning or sampling from outside, or designing the task so that nobody goes in, removes the risk rather than managing it.

Isolate the space. Lock out and tag out mechanical and electrical energy, blank or disconnect incoming lines, and prove the isolation rather than assuming it.

Test the atmosphere before entry. Oxygen, flammable gases and vapours, and any contaminant the space may hold, using calibrated equipment and a competent person. Keep monitoring while the space is occupied where the risk calls for it.

Purge and ventilate. Mechanical ventilation is standard, and never with oxygen.

Post a standby person. Someone stays outside, keeps continuous communication with the people inside, controls access and starts the emergency response. The standby person does not enter.

Plan the rescue and resource it. Calling emergency services is not a rescue plan on its own, and the arrangements have to be workable with the people and equipment actually on site at the time.

Confirm competence. Entrants, standby people and supervisors all need confined space training, which is specific and is not part of a general site induction.

Sign the space. Signage keeps people from wandering in while the work is under way.

Calling a trench a confined space. Excavations are controlled under their own provisions. Treating them as confined spaces confuses crews about what the permit system is for, while the controls that actually apply to excavation get less attention.

Testing once, at the top. Atmospheres stratify. Gases heavier than air sit low and lighter ones collect high, so testing has to happen at the depths people will occupy, and before anyone breaks the plane of the opening.

Issuing a permit for the shift instead of the entry. Conditions change when work stops, when ventilation is switched off, and overnight. Each entry needs its own authorisation.

Using the SWMS instead of a permit. A safe work method statement describes how the task is carried out. The permit authorises this entry, into this space, now. Both are needed and neither substitutes for the other.

Rescue by whoever is nearest. Untrained rescuers entering a space that has already overcome somebody is the classic way a single fatality becomes several.

Leaving the completion sign off blank. If nobody closes the permit, nobody knows the space is clear, and the next crew inherits an unknown.

Assuming the specialist has it covered. A confined space subcontractor brings its own permit system, but the principal contractor still has to see it, check the competencies, and confirm that the rescue arrangements work on this site.