• Confined Spaces: No Small Danger

    LOBO used in a confined space.Toxic air, flammable vapours and the only way out is through a small opening – this situation is just one of many scenarios that describe what it’s like to work in a confined space. While hazards can be found in every type of workspace, confined spaces have the potential to be even more hazardous. Learn more about some of the hazards with working in confined spaces and what you can do to control the risks.

    What is a confined space?

    Generally speaking, a confined space is an enclosed or partially enclosed space that is not primarily designed or intended for human occupancy, has a restricted entrance or exit, and can represent a risk to the health and safety of anyone who enters, due to one or more of the following factors:

    • its design, construction, location or atmosphere
    • the materials or substances in it
    • work activities being carried out in it, or the
    • mechanical, process and safety hazards present.

    Confined spaces can be found in almost any workplace. Examples include: silos, vats, hoppers, utility vaults, water cisterns, clean water wells, tanks, ship holds, sewers, pipes, access shafts, truck or rail tank cars, aircraft wings, boilers, conveyors, cellars, tunnels, manholes, manure pits, storage bins and other such spaces that workers could enter to perform work. Ditches or trenches may also be a confined space when access or a way out is limited.


    All hazards found in a regular workspace can also be found in a confined space. The main hazards associated with confined spaces include: oxygen deficiency or enrichment, fire or explosion, toxicity, and drowning.


    Too little oxygen can cause brain damage, the loss of consciousness, and potential suffocation. Too much oxygen can increase the risk of fire or explosion. Natural ventilation alone will often not be sufficient to maintain breathable quality air.

    A high percentage of deaths in confined spaces result from oxygen deficiency and lack of quality air testing. Of the workers killed each year while working in confined spaces, many of them have been would-be rescuers who often suffer the same fate as those they are attempting to save.

    Fire and explosions

    Inadequate ventilation can result in an accumulation of gases or dusts that can combust when exposed to electricity, a welding spark, or open flame.


    Gases from work activities such as painting and welding, and sources such as liquid manure or compost can produce gases including hydrogen sulfide, methane, carbon monoxide, and solvent vapours that can cause dizziness, loss of consciousness, permanent damage to health, and death.


    In the event of a flood or engulfment by a free-flowing solid (for example grain in a silo), the entrance or exit of the confined space may be obstructed, preventing the worker from getting out in time. Drowning can also occur by falling into holding tanks, ponds and pits filled with liquid.

    More hazardous than other work spaces

    All of these hazards may not be obvious so a person qualified with the proper training and experience must conduct a confined space hazard assessment before any workers enter the space, considering these factors:

    • Self-rescue by the worker is more difficult.
    • Rescue of the victim is more difficult. The interior configuration of the confined space often does not allow easy movement of people or equipment within it.
    • Conditions can change very quickly and without warning.
    • The space outside can impact the conditions inside the confined space and vice versa.
    • Work activities may introduce hazards not present initially.

    Many factors need to be evaluated when looking for hazards in a confined space. An error in identifying or evaluating potential hazards can put the worker’s life in danger.

    Preparation and prevention

    To effectively control the risks associated with working in a confined space, a Confined Space Hazard Assessment and Control Program should be implemented. Before putting together this program, make sure to review the specific regulations that apply to your workplace. All jurisdictions in Canada have varying regulations dealing with confined space entry.

    Workers should not enter the confined space until it is made safe to do so by taking precautions.

    For each job, determine if it is absolutely necessary that the work be done inside the confined space. In some cases it may be possible to do the work outside the confined space.

    Air quality testing needs to be performed by a qualified person trained in using detection equipment. Always make sure that the testing equipment is properly calibrated and maintained. Air sampling should show that there are safe limits of oxygen content in the confined space, hazardous gases are not present, and that ventilation is working properly. This testing should be ongoing while work is being done.

    Remove or restrict any liquids or free-flowing solids in the confined space to eliminate the risk of drowning or suffocation. All pipes should be physically disconnected or isolation blanks bolted in place; closing valves is not sufficient.

    Entry and exit openings for the confined space must be large enough to allow the passage of a person using personal protective equipment (PPE).

    What employers can do

    • Have a confined space program that includes written procedures
    • Identify confined spaces
    • Post warning signs and secure entry to confined spaces
    • Determine the hazards for each space
    • Develop confined space entry plans for each space
    • Train workers in safe work procedures specific to the work being done in the confined space
    • Use an entry permit system

    What workers can do

    • Recognize confined spaces
    • Know the hazards
    • Follow safe work procedures when in a confined space
    • Stay aware of changing conditions while performing the work
    • Know when to stay out of confined spaces
    • Don’t attempt to rescue others without proper training and equipment


    Originally posted by CCOHS July 2015

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