Preface This is the third edition of CSA Z275.3, Occupational safety code for work in compressed air environments. It supersedes the previous editions, published in 1986 and 1974 under the title Occupational Safety Code For Construction Work in Compressed Air. Scope 1.1 This Standard applies to all work in compressed air environments at pressures above 20 kPa (3 psig) and sets forth requirements for the health and safety of workers exposed to these environments. Note: In addition to the requirements of this Standard for the protection of workers, requirements can be prescribed by the authority having jurisdiction. 1.2 This Standard applies to every shaft, tunnel, caisson, enclosure, and similar type of work site in which a worker is, or is likely to be, subjected to working in compressed air. 1.3 This Standard does not apply to divers or workers employed in diving bells (see CAN/CSA-Z275.2) and to hyperbaric treatment facilities (see CSA Z275.1). 1.4 In CSA Standards, \"shall\" is used to express a requirement, i.e., a provision that the user is obliged to satisfy in order to comply with the standard; \"should\" is used to express a recommendation or that which is advised but not required; and \"may\" is used to express an option or that which is permissible within the limits of the standard. Notes accompanying clauses do not include requirements or alternative requirements; the purpose of a note accompanying a clause is to separate from the text explanatory or informative material. Notes to tables and figures are considered part of the table or figure and may be written as requirements. Annexes are designated normative (mandatory) or informative (non-mandatory) to define their application. 1.5 The values given in SI units are the units of record for the purposes of this Standard. The values given in parentheses are for information and comparison only. All air pressures specified in this Standard are expressed in kPa gauge (above atmospheric pressure) with the equivalent psi gauge units shown in parentheses.