Preface: This is the seventh edition of CSA Z275.2, Occupational safety code for diving operations. It supersedes the previous editions published in 2015, 2011, 2004, 1992, 1982, and 1974. It is part of a series of Standards on diving and caisson systems covering hyperbaric facilities, occupational diving, and construction work in compressed air environments. The significant changes to this edition include the following: a) new provisions for SCUBA diving, combining "restricted" and "unrestricted" categories into one "occupational SCUBA" category; b) clarification of crew size requirements for SCUBA diving, including a new requirement to conduct a dive site risk assessment in order to determine appropriate crew size (Clause 7.5); c) incorporation of updated crew size requirements for surface-supplied diving (Clause 8.2) as published in the 2018 Amendment to Z275.2-15; d) expanded references to IMCA guidelines for offshore diving (Clauses 9.2and 9.3); e) clarification of requirements for four categories of contaminated diving (Clause 11and Table 8); f) provision of further guidance on nitrox diving, along with new definitions (Clause 12); and g) addition of a new Annex (K) on "diver rescue methods". This Standard has also been harmonized with regulations, standards, guidelines, and codes developed by the Canadian Oil and Gas Lands Administration (COGLA), the Oil and Gas Producers (OGP), the International Marine Contractors Association (IMCA), and NORSOK. This Standard is not intended to supersede the requirements of applicable occupational safety and health regulations. Criteria in this Standard have been written in a manner that allows the user to comply both with the Standard and applicable legislated requirements throughout Canada. This Standard is not intended for use as a diving or procedure manual. It is designed to be inflexible in those matters that experience has shown to be critical to the safety of the diver, and yet flexible in those areas where the responsibility and considered judgment of operators provide the highest degree of safety in specialized operations. Specific exposure tables and decompression schedules are not included in this Standard in view of the fact that a number of well-tested and authoritative tables are available for use by divers and for adoption by the regulatory authorities. CSA Group acknowledges that the development of this Standard was made possible, in part, by the financial support of the Canadian government departments responsible for occupational health and safety for the development of this edition, the Diver Certification Board of Canada, the Canadian Association of Diving Contractors, and several commercial diving companies. This Standard has been developed in compliance with Standards Council of Canada requirements for National Standards of Canada. It has been published as a National Standard of Canada by CSA Group. Scope: 1.1 General 1.1.1 This Standard applies to occupational diving operations conducted in connection with all types of work and employment, and describes the requirements for occupational safety. Note: It is recognized that certain underwater tasks might require specialized standards of practice and/or operational techniques that differ from the requirements of this Standard yet may be acceptable to the authority having jurisdiction. Users should consult applicable provincial and federal occupational safety and health regulations to determine whether they impose safety requirements additional to or more stringent than those of this Standard. 1.1.2 This Standard addresses equipment requirements and operational procedures for the following diving systems: a) SCUBA diving systems (see Clause 7); b) surface-supplied diving systems (see Clauses 8and 9); c) deep diving systems (see Clause 9); d) one-atmosphere diving systems (see Clause 10); and e) diving in contaminated environments (see Clause 11). 1.2 Limitations 1.2.1 This Standard does not apply to scientific diving as defined in Clause 3. 1.2.2 This Standard does not apply to diving operations performed solely for sport or recreation. 1.2.3 This Standard does not include work techniques associated with underwater diving operations. 1.3 Terminology In this Standard, "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. 1.4 Units of measurement The values given in SI units are the units of record for the purposes of this Standard. Where values are given in parentheses, they are for information and comparison only.