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Confined Space Entry- Safe Working Procedure

28-May-2010 [304]

Part of OHSA

Confined Space Entry- Safe Working Procedure (pdf)


The purpose of this safety procedure is to specify the general requirements, in accordance with the confined space regulations of the Occupational Health & Safety Act, for entry into confined spaces as part of the City of Toronto’s confined space program.


“acceptable atmospheric levels” means that, (a) the atmospheric concentration of any explosive or flammable gas or vapour is less than,

(i) 25 per cent of its lower explosive limit, if the worker is performing only inspection work that does not produce a source of ignition,

(ii) 10 per cent of its lower explosive limit, if the worker is performing only cold work and

(iii) 5 per cent of its lower explosive limit, if the worker is performing hot work and is following all provisions of Safe Working Procedure, SWP023.05, Hot Work Permit System.

(b) the oxygen content of the atmosphere is at least 19.5 per cent but not more than 23 per cent by volume; and

(c) the exposure to atmospheric contaminants does not exceed any applicable level set out in a regulation made under the Act such as The Control of Exposure to Biological or Chemical Agents and Designated Substances. “adequate”, when used in relation to a procedure, plan, material, device, object or thing, means that it is,

(a) sufficient for both its intended and its actual use; and

(b) sufficient to protect a worker from occupational illness or occupational injury.

“anoxic” means an absence or near absence of oxygen and therefore, by regulation, an atmosphere less than 19.5% oxygen.

“assessment” means an assessment of hazards with respect to one or more confined spaces in a workplace.

“atmospheric hazards” means,
(a) the accumulation of flammable, combustible or explosive agents, SAFE WORKING PROCEDURE Confined Space Entry

(b) an oxygen content in the atmosphere that is less than 19.5 per cent or more than 23 per cent by volume, or

(c) the accumulation of atmospheric contaminants, including gases, vapours, fumes, dusts or mists, that could,

(i) result in acute health effects that pose an immediate threat to life, or

(ii) interfere with a person’s ability to escape unaided from a confined space.

“cold work” means work that is not capable of producing a source of ignition.

“confined space” means a fully or partially enclosed space,

(a) that is not both designed and constructed for continuous human occupancy; and

(b) in which atmospheric hazards may occur because of its construction, location or contents or because of work that is done in it.

“doable” means capable of being done.

“emergency work” means work performed in connection with an unforeseen event thatinvolves an imminent danger to the life, health or safety of any person.

“hot work” means work that is capable of producing a source of ignition.

“Inerting” means displacing oxygen from a space using an inert gas (such as nitrogen, carbon dioxide or argon) to remove the hazard of fire or explosion.

“plan” means a plan for one or more confined spaces in a workplace, as described in this procedure.

“practicable” means doable.

“purging” means removing contaminants inside the confined space by displacement with air to achieve acceptable atmospheric levels.

“qualified worker” means a person with adequate knowledge, training and experience to perform the specific assigned work; a qualified worker is equivalent to a competent worker in the Construction Regulations.

“Ventilation” means the continuous provision of fresh air into the confined space by mechanical means to maintain acceptable atmospheric levels.


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