Confined space hazard assessment

A confined space hazard assessment is a written review, done by a competent person before anyone enters, of everything inside, around and connected to a space that could hurt a worker. It covers the space itself and the work planned in it, and it sets the controls that will go on the entry permit. Without it, the permit is just a form.

When to do an assessment

Every identified confined space needs a written assessment before the first entry. Similar spaces, such as a row of identical manholes, can sometimes share one assessment if the conditions really are the same, but differences in connected piping, contents or location matter. The assessment should be reviewed:

• Before each entry, to confirm conditions have not changed
• When the work to be done inside changes
• After changes to equipment, piping, processes or materials stored in the space
• After an incident or near miss
• At the intervals your program or province requires

Who should do it

Provincial rules generally require the assessment to be done by a competent person: someone with the knowledge, training and experience to recognize the hazards of that space and the work. In practice it works best as a small team, including someone who knows the process or equipment, someone who will supervise the entry, and a worker who has done the job before. Worker input often brings out hazards that are not in any drawing.

What to assess

The space itself

• Size, shape and internal structures such as baffles, agitators, ladders and platforms
• Number, size and location of entry and exit openings, and whether a rescuer with equipment could fit through them
• Sloped or converging walls, deep sumps or other features that could trap a worker
• Floor conditions, residues and slip hazards

Atmospheric hazards

• Oxygen deficiency or enrichment, and what could cause either
• Flammable gases, vapours and dusts from contents, residues, leaks or nearby sources
• Toxic gases such as hydrogen sulphide, carbon monoxide, ammonia or solvent vapours
• Gases created by the work: welding fumes, coatings, cleaning chemicals, exhaust from engines
• Gases that may be released when sludge or scale is disturbed

The assessment should specify which gases to test for, where in the space to test, and how often. See Atmospheric testing and gas detection for how testing is done.

Engulfment and flooding

Consider any liquid or loose solid that could flow into the space or collapse onto a worker, including material from connected lines, bridged product in a hopper, groundwater or storm water.

Energy sources

List every source of energy that could harm someone inside: electrical, mechanical, hydraulic, pneumatic, thermal, chemical and gravity. Identify how each one will be isolated, whether by lockout, blanking or blinding lines, disconnecting, or double block and bleed, and how isolation will be verified.

Physical and environmental hazards

Heat and cold, noise, poor lighting, radiation sources, biological hazards such as sewage, and the strain of working in awkward postures all belong in the assessment.

Hazards outside the space

Traffic near a manhole, nearby hot work, vehicle exhaust drawn into a ventilation fan, or other crews working on connected systems can all affect the people inside.

From hazards to controls

For each hazard, the assessment should name the control, working down the hierarchy of controls. First ask whether entry can be avoided entirely, for example by using cameras, remote cleaning tools or doing the work from outside. Then look at engineering controls such as isolation and mechanical ventilation, administrative controls such as permits, testing frequency and time limits, and finally personal protective equipment such as respirators, harnesses and retrieval lines. Our guide to the hierarchy of controls explains the order and why it matters.

A useful assessment also decides:

• Whether the space requires an entry permit and what it must contain
• Whether continuous gas monitoring is needed
• The minimum training for entrants, attendants and supervisors
• The communication method between entrant and attendant
• Rescue method, equipment and team
• Conditions that require everyone to leave the space

Keeping the assessment useful

Write the assessment in plain language so the supervisor issuing the permit and the workers entering can read it and understand it. Keep it with the permit file, attach photos of the space and its isolation points, and record who did the assessment and when. A short, specific assessment that people read is more protective than a long generic one that nobody opens.

How ehZee can help

We complete space-by-space assessments with your team, document isolation points and rescue considerations, and turn the results into permits and procedures. Our confined space programs service describes how that work is done.

Common questions