OSHA Diving Regulations

This instruction provides guidance to OSHA National, Regional, and Area Offices; industry employer and employee groups; State programs; and federal agencies concerning OSHA's policy and procedures for implementing intervention and inspection programs to reduce injuries, illnesses and fatalities, or eliminate workplace hazards regarding commercial diving operations. This instruction provides tools to support intervention and inspection programs in the commercial diving industry.

The initial standard for commercial diving operations was issued in the Federal Register, July 22, 1977 (see  42 FR 37650).  The preamble, from pages 37650 to 37668, contains information and background on the purposes and intent of the standard.

In 1979, 29 CFR 1910.411 Medical requirements of the original diving standards promulgated on July 22, 1977, was challenged successfully in a court case, Taylor Diving & Salvage Company v. Department of Labor, 599 F.2d 622 (5^th Circuit 1979); OSHA subsequently  removed this section from 29 CFR Part 1910, Subpart T.

On November 26, 1982, OSHA published a provision (see 29 CFR 1910.401(a)(2)(iv)) exempting scientific diving from coverage under 29 CFR Part 1910, Subpart T (see Federal Register notice 47 FR 53357).  This exemption applied only when:  (1) the diving operation meets the Agency's definition of scientific diving; (2) the diving operation is part of a diving program that uses a safety manual; and (3) the diving program is directed and controlled by a diving-control board that conforms to specified criteria.  However, the United Brotherhood of Carpenters and Joiners (UBCJ) subsequently challenged this exemption in a federal appellate court (see United Brotherhood of Carpenters and Joiners v. Department of Labor, No. 82-2509 (D.C. Cir. 1982)).  On April 4, 1984, this court issued an unpublished memorandum and order in which it stated that OSHA must provide the UBCJ with an opportunity to submit evidence to the public record regarding the exemption, and make a clear distinction between commercial and scientific diving.  The Agency then reopened the public record to allow the UBCJ and other members of the public to submit additional evidence regarding the exemption, and to propose interpretive guidelines that it would be used to distinguish between commercial and scientific diving (see Federal Register notice 49 FR 29105).  After carefully considering the new evidence submitted to the record, OSHA published on January 9, 1985, a notice in the Federal Register reinstating the conditions for the scientific exemption specified earlier for 29 CFR 1910.401(a)(2)(iv), and establishing the interpretive guidelines by which it will be determined whether the diving operation is scientific or commercial (see Federal Register notice 47 FR 53357).

On February 17, 2004 (see Federal Register notice 69 FR 7351), OSHA amended 29 CFR Part 1910, Subpart T -  ("Commercial Diving Operations"), to allow recreational diving instructors and diving guides to comply with an alternative set of requirements instead of the decompression chamber requirements in the existing 29 CFR Part 1910, Subpart T standards.  The final rule applies only when these employees engage in recreational diving instruction and diving-guide duties; use an open-circuit, a semi-closed-circuit, or a closed-circuit self-contained underwater-breathing apparatus supplied with a breathing gas that has a high percentage of oxygen mixed with nitrogen; dive to a maximum depth of 130 feet of sea water; and remain within the no-decompression limits specified for the partial pressure of nitrogen in the breathing-gas mixture. This final rule became effective on March 18, 2004.

                                                       1.            Acfm:  Actual cubic feet per minute.

                                                       2.            ASME Code or equivalent:  ASME (American Society of Mechanical Engineers) Boiler and Pressure Vessel Code, Section VIII, or an equivalent code which the employer can demonstrate to be equally effective.

NOTE:  "Equivalent" means equipment that is designed, built, and maintained to standards that will provide employees with at least the same level of protection as equipment that meets the ASME Boiler and Pressure Vessel Code, Unfired Pressure Vessels, Section VIII.  The employer shall be responsible for demonstrating equivalency.  Questions regarding equivalency should be referred to OSHA's National Office, Office of Maritime Enforcement.

                                                       3.            ATA:  Atmosphere absolute.

                                                       4.            Bell:  An enclosed compartment, pressurized (closed bell) or unpressurized (open bell), which allows the diver to be transported to and from the underwater work area and which may be used as a temporary refuge during diving operations.

                                                       5.            Bottom time:  The total elapsed time measured in minutes from the time when the diver leaves the surface in descent to the time that the diver begins ascent (i.e., the diver "leaves the bottom").

                                                       6.            Bursting pressure:  The pressure at which a pressure containment device would fail structurally.

                                                       7.            Cylinder:  A pressure vessel for the storage of gases.

                                                       8.            Decompression chamber:  A pressure vessel for human occupancy such as a surface decompression chamber, closed bell, or deep diving system used to decompress divers and to treat decompression sickness.

NOTE:  As used in this standard, the term "decompression chamber" refers to any pressure vessel for human occupancy used to decompress divers and to treat decompression sickness.  A closed bell, if used as a decompression chamber, shall meet the design criteria stated in 29 CFR 1910.430(f).

                                                       9.            Decompression sickness:  A condition with a variety of symptoms which may result from gas or bubbles in the tissues of divers after pressure reduction.

                                                   10.            Decompression table:  A profile or set of profiles of depth-time relationships for the ascent rates and breathing mixtures to be followed after a specific depth-time exposure or exposures.

                                                   11.            Dive location:  A surface or vessel from which a diving operation is conducted.

NOTE:  The term "dive location" refers to the surface location from which diving operations are conducted such as a vessel, barge, wharf, pier, riverbank, or offshore rig, and does not mean the diver's underwater work location.

                                                   12.            Dive-location reserve breathing gas:  A supply system of air or mixed-gas (as appropriate) at the dive location which is independent of the primary supply system and sufficient to support divers during the planned decompression.

                                                   13.            Dive team:  Diver and support employees involved in a diving operation, including the designated person-in-charge.

                                                   14.            Diver:  An employee working in water using an underwater apparatus which supplies compressed breathing gas at the ambient pressure.

                                                   15.            Diver-carried reserve breathing gas:  A diver-carried supply of air or mixed-gas (as appropriate) sufficient under standard operating conditions to allow the diver to reach the surface, another source of breathing gas, or to be reached by a standby diver.

                                                   16.            Diving mode:  A type of diving requiring specific equipment, procedures and techniques (SCUBA, surface-supplied air, or mixed-gas).

                                                   17.            Fsw:  Feet of seawater (or equivalent static pressure head).

NOTE:  An example of equivalent static pressure head would be the pressure of air inside a pressurized decompression chamber.

                                                   18.            Heavy gear:  Diver-worn deep-sea dress, including helmet, breastplate, dry suit, and weighted shoes.

NOTE:  Advances in diving equipment and technology have led to heavy gear that does not include a breastplate.  Surface-supplied diving gear, including helmet, dry suit, and weighted shoes (i.e., with the helmet directly connected to the dry suit, forming a self-contained pressure envelope for the diver) constitutes heavy gear as well.

                                                   19.            Hyperbaric conditions:  Pressure conditions in excess of surface pressure.

                                                   20.            Inwater stage:  A suspended underwater platform that supports a diver in the water.

                                                   21.            Liveboating:  The practice of supporting a surfaced-supplied air or mixed-gas diver from a vessel which is underway.

                                                   22.            Mixed-gas diving:  A diving mode in which the diver is supplied in the water with a breathing gas other than air.

NOTE:  For diving operations, air is a mixture of oxygen and nitrogen with an oxygen content of 19.5 - 23.5 percent.  Breathing gas mixtures with an oxygen content less than 19.5 percent or greater than 23.5 percent, or that use gases other than oxygen and nitrogen (excluding trace gases such as those found in compressed atmospheric air), constitute a mixed gas for the purposes of commercial diving. 

                                                   23.            No-decompression limits:  The depth-time limits of the "no-decompression limits and repetitive dive group designation table for no-decompression air dives," U.S. Navy Diving Manual or equivalent limits which the employer can demonstrate to be equally effective.

NOTE:  The term "no-decompression limits" applies to those depth-time combinations for which decompression of the diver is not required.  The no-decompression tables from the U.S. Navy Diving Manual are included in Appendix D of this instruction.

                                                   24.            Psi(g):  Pounds per square inch (gauge).

                                                   25.            Scientific diving:  Means diving performed solely as a necessary part of a scientific, research, or educational activity by employees whose sole purpose for diving is to perform scientific research tasks.  Scientific diving does not include performing any tasks usually associated with commercial diving such as but not limited to:  placing or removing heavy objects underwater; inspection of pipelines and similar objects; construction; demolition; cutting or welding; or the use of explosives.

NOTE:  Additional guidance is provided in Appendix C of this instruction.

                                                   26.            SCUBA diving:  A diving mode independent of surface supply in which the diver uses open-circuit self-contained underwater breathing apparatus.

                                                   27.            Standby diver:  A diver at the dive location available to assist a diver in the water.

NOTE:  The requirement that the standby diver be at the dive location, which is a location on the surface (such as the shore, a pier, or a dock) or on the deck of a vessel, eliminates the possibility that another diver in the water or at another dive location would be considered a standby diver.  Standby divers do not necessarily have to be fully dressed, but must be available to render the necessary assistance in a timely manner.  The term "available" means to be clothed and equipped, and ready to enter the water at a moment's notice.  Gear such as face masks, air cylinders, and harnesses can be donned quickly, and need not be worn until the standby diver is required to enter the water.

                                                   28.            Surface-supplied air diving:  A diving mode in which the diver in the water is supplied from the dive location with compressed air for breathing.

                                                   29.            Treatment table:  A depth-time and breathing-gas profile designed to treat decompression sickness.

                                                   30.            Umbilical:  The composite hose bundle between a dive location and a diver or diving bell, or between a diver and a diving bell, which supplies the diver or diving bell with breathing gas, communications, power, or heat as appropriate to the diving mode or conditions, and includes a safety line between the diver and the dive location.

                                                   31.            Volume tank:  A pressure vessel connected to the outlet of a compressor and used as an air reservoir.

                                                   32.            Working pressure:  The maximum pressure to which a pressure containment device may be exposed under standard operating conditions.

 29 CFR 1910.410 Qualifications of dive team

                                                       1.            The level of experience or training required by the standard depends upon the job the employees are required to do.  All dive-team members must have either experience or training in the use of tools, equipment, systems, techniques, operations, operational procedures, and emergency procedures that are pertinent to, and necessary for, the assigned tasks for the diving mode (i.e., SCUBA, surface-supplied air, or mixed-gas diving).  It is essential that those dive-team members who are exposed to hyperbaric conditions, or those members who control the exposure of others, have knowledge of the physiological effects of diving and the related effects of pressure.  Accordingly, this standard also requires that employees be trained in diving-related physics and physiology.  Employee qualifications achieved through field experience or classroom training, or both, may be used to meet the requirements of the standard.  For example:

                                                                               a.            Most divers begin as tenders and advance to diving status after a period of field experience and/or classroom training.  A diving-tender trainee performing on-the-job training will be assigned as a tender only under the supervision of a qualified diver.

                                                                              b.            Tenders are members of the dive team who provide surface-support to divers at the diving location.  A tender employed in shallow-water air diving is required to have a basic understanding of the breathing-air system, the operating and emergency procedures, and knowledge of the care and use of equipment.  See Appendix E of this instruction for additional guidance regarding the responsibilities and duties of tenders.

                                                                               c.            A mixed-gas diver conducts underwater work using mixed-gas as the breathing medium.  Mixed-gas divers are required to have an advanced understanding of diving, including a working knowledge of mixed-gas equipment such as a decompression chamber, diving bell, and mixed-gas breathing supply system, and operational and emergency procedures associated with mixed-gas diving.  In addition, the mixed-gas diver must have an understanding of the physics and physiology of mixed-gas diving.

                                                                              d.            Chamber operators are required to have experience or training in conducting decompression procedures, knowledge of the physics and physiology of decompression, and the operation of the decompression equipment to which they are assigned.

                                                                              e.            Each dive-team member must be trained in cardiopulmonary resuscitation and standard first aid.  The American Red Cross standard course or equivalent training is specified by the standard.  Employees completing this training are issued a card certifying that they have successfully completed the course.  Any first-aid training meeting the requirements of 29 CFR 1910.151(b) and 1926.50(c) will meet the requirements of the standard (such as first-aid courses offered by the American Heart Association, American Petroleum Institute, National Safety Council, U.S. Bureau of Mines, and American College of Orthopedic Surgeons).

                                                       2.            The following methods may be used to check diving qualifications:

                                                                               a.            Field experience.

                                                                                                         i.            Employment records.

                                                                                                       ii.            Written statements from previous employers.

                                                                                                      iii.            Written statements from diving officers or commanding officers (military).

                                                                                                     iv.            Field operations records.

                                                                                                       v.            The employee's diving logs.

                                                                              b.            Diving proficiency.

                                                                                                         i.            Company field operations records.

                                                                                                       ii.            Federal service operations records (such as from the Army Corps of Engineers, NOAA, or military).

                                                                                                      iii.            The employee's diving logs.

                                                                               c.            Technical training.

                                                                                                         i.            Federal service qualification certificates (such as from the Army Corps of Engineers, NOAA, or military).

                                                                                                       ii.            Diving school certificates of completion.

                                                                                                      iii.            Company training program completion statements or equivalent proof of competency.

                                                                                                     iv.            Valid commercial diver certification card for the appropriate training level issued by the Association of Diving Contractors International.

                                                       3.            Under 29 CFR 1910.410(b)(1), employers must generally assign tasks to dive-team members according to their experience and training.  Additionally, the phrase "known to the employer" in 29 CFR 1910.410(b)(3) means that the designated person-in-charge must inquire into each dive-team member's health prior to a task assignment.  The employer also is required in 29 CFR 1910.421(f)(2) to advise dive-team members of the procedures for reporting physical problems or adverse physiological effects during and after diving.  Consistent with these provisions, an employer cannot require dive-team members to dive or otherwise work under hyperbaric conditions when they:  (1) have any ailment that is likely to adversely affect the safety or health of any member of the dive team; (2) lack the necessary training or education; or (3) refuse to work under such conditions. However, should a diver request termination during a dive, it may be necessary to prolong the diver's exposure to hyperbaric conditions to complete decompression or medical recompression treatment to avoid serious physical harm or death to the diver.

                                                       4.            Under 29 CFR 1910.410(c), the designated person-in-charge (DPIC)(commonly referred to as the "diving supervisor" or the "diving foreman") is immediately responsible for the safety and health of the dive team.  The DPIC can be the employer or an employer representative chosen by the employer.  The DPIC shall have experience in, and knowledge of, all phases of the diving operation for which he/she is responsible.  The DPIC shall be stationed at the dive location, and shall not be stationed at another dive location (i.e., he/she must be stationed at one dive location and be responsible only for the diving operation at that location).  The DPIC can be a diver, when qualified as a diver, and when another dive-team member is available at the dive location.  This dive-team member must be trained and capable of performing the necessary functions of the DPIC's duties, when the DPIC is a diver in the water.  The qualifications of the DPIC can be checked using the same methods listed in section XV, paragraph C.2, of this instruction.

 29 CFR 1910.420 Safe practices manual                              A.             

                                                       1.            This standard requires that the employer develop and maintain a safe practices manual that includes information and procedures relating to the safety and health of the dive-team members.  The manual must contain a copy of the commercial diving operations standard and a statement of the employer's policy for ensuring compliance with the standard.  The employer may refer to the safe practices manual as the diving manual, employer's operational log, or diving guide.  The manual must be at the dive location and available to all dive-team members.

                                                       2.            The safe practices manual must provide a written operational procedure for each diving mode used by the employer.  The CSHO shall review the manual to determine if it contains safety procedures and checklists for diving operations, assignments and responsibilities of the dive-team members, equipment procedures and checklists, and emergency procedures (at a minimum:  fire, equipment malfunction or failure, adverse environmental conditions, and medical illness and injury).  The safe practices manual guidance and procedures must be supplemented with additional information specific to each diving operation.  This supplemental information is obtained during pre-dive planning and assessment (see 29 CFR 1910.421(d)), and promulgated to the dive-team members during the employee briefing (see 29 CFR 1910.421(f)).

NOTE:  The "Consensus Standards for Commercial Diving and Underwater Operations" published by the Association of Diving Contractors International is recognized as meeting the general requirements of a safe practices manual.

 29 CFR 1910.421 Pre-dive procedures                              A.             

                                                       1.            The provisions of this section must be followed by the employer for all diving modes, with the designated person-in-charge responsible for overall compliance with these provisions and briefing dive-team members.

                                                       2.            29 CFR 1910.421(b) Emergency aid.  The CSHO shall determine whether the emergency aid list is complete and is available to all dive-team members.  This list must contain the telephone or call numbers of:  the nearest operational decompression chamber (if a chamber is not required at the dive location); accessible hospital(s); the available physician(s); the means of transportation available for use in the event of an emergency; and the nearest U.S. Coast Guard Rescue Coordination Center.

                                                       3.            29 CFR 1910.421(c) First aid supplies.  The CSHO shall determine whether a first-aid kit is available at the dive location.  The first-aid kit provided at the dive location must be appropriate for the diving operations, and approved by a physician.  If it is to be used in a pressure chamber, such as a decompression chamber or a diving bell, the first-aid kit must be suitable for use under hyperbaric conditions because some items in a standard kit (such as bottles of liquid, mercury thermometers, or ammonia ampoules) may burst under pressure. In addition to any other first-aid or medical supplies, the kit must include an American Red Cross standard first-aid handbook, or an equivalent handbook, and a bag-type resuscitator with a transparent hose and mask (so that the operator can see that the diver's air passages are clear).

                                                       4.            29 CFR 1910.421(d) Planning and assessment.  This provision requires the employer to include in the planning of a diving operation an assessment of the safety and health features of the diving mode, surface and underwater conditions and hazards, primary and reserve breathing-gas supply, thermal protection, diving equipment and systems, dive-team assignments and the physical fitness of dive-team members (including any impairments known to the employer), repetitive dive designation or residual inert-gas status of divers, decompression chamber procedures (including any altitude corrections), and emergency procedures.  The employer typically assigns this planning task to the designated person-in-charge.  Most of the information required by this provision should be in the safe practices manual (see 29 CFR 1910.420). Some information may not be found in the manual because it cannot be determined until the dive team reaches the dive location.  The CSHO can question the dive-team members to determine that the employer has complied with the requirements of this provision.

NOTE:  29 CFR 1910.421(d) can be cited for any identified hazard that was not addressed properly by an employer when they planned and conducted an assessment of the diving operation or work to be performed.

                                                       5.            29 CFR 1910.421(e) Hazardous activities.  Hazards encountered during diving operations such as weather, water temperature, current, and bottom conditions must be recognized and taken into account during the planning and execution of the operation.  When other operations being conducted in the vicinity (such as dredging, marine traffic, or movement of materials directly above the dive location and/or area of the dive) are likely to interfere with the diving operation, the designated person-in-charge shall plan the operation only after appropriate coordination with persons responsible for the other activities so that any hazard exposures to the diver(s) or other dive-team members will be eliminated.  Failure to plan for such conditions, or to coordinate activities, shall be a basis for a citation.

                                                       6.            29 CFR 1910.421(f) Employee briefing.  The employee briefing is usually conducted by the designated person-in-charge just prior to the diver(s) entering the water.  The dive-team members shall be briefed on the tasks to be undertaken, safety procedures for the diving mode, any unusual hazards or environmental conditions likely to affect the safety of the diving operation, and any modifications to operating procedures necessitated by the specific diving operation.  The designated person-in-charge also must advise the dive-team members of the procedures for reporting physical problems or adverse physiological effects during and after the dive.  It is particularly important that the designated person-in-charge inquire into each dive-team member's current state of physical fitness before making assignments.  To determine compliance, the CSHO can question dive-team members and observe the diving operation, if one is ongoing.

                                                       7.            29 CFR 1910.421(g) Equipment inspection.

                                                                               a.            The equipment-inspection requirement prior to each dive relates directly to the equipment-checklist requirement in the safe practices manual.  The breathing-supply system, including reserve breathing-gas supplies, masks, helmets, thermal protection, and diving bell-handling mechanisms (when appropriate) must be inspected prior to each diving operation.  Pre-dive equipment inspection items are those that are critical for the safety of the dive operation.  For surface-supplied diving, the breathing-supply system equipment inspection includes diving umbilicals as defined in 29 CFR 1910.402, Definitions.  The inspection of an umbilical includes a visual inspection of the breathing-gas hose, communications cable, and the safety line between the diver and the dive location, and power cables and hot-water hoses as appropriate.  This inspection ensures that the umbilical has the required components, that the components are properly rigged and married together, and that all components are in good working condition (no leaks, tears, or damage).  Umbilicals being used for diving operations with missing components or components in a condition that pose a hazard to the diver or dive team (such as a cut breathing-gas hose, power cable with bare wires exposed, or excessively frayed safety line) will be cited under 29 CFR 1910.421(g).

                                                                              b.            Compliance with the pre-dive inspection requirements usually can be determined only by observation (such as systems, equipment, processes and procedures), and questioning the employees.  This standard makes no distinction between employer-provided equipment and employee-provided equipment with regard to the pre-dive inspection requirement.  While an employee may make such inspections, it is the employer who is responsible for ensuring compliance with all equipment requirements of the standard.

                                                       8.            29 CFR 1910.421(h) Warning signal.

                                                                               a.            The following paragraphs describe the two distinctions made in the requirements for displaying the warning signal for commercial diving operations:

                                                                                                         i.            29 CFR 1910.421(h) requires the warning signal to be displayed when diving from surfaces other than vessels such as wharves, piers, pilings, jetties, fixed caissons, levees, dikes, dams, breakwaters, and artificial islands (secured to the sea floor).  Violations of this requirement shall be cited under this section.

                                                                                                       ii.            The requirement for displaying the warning signal when the dive location is located on a vessel is covered by the U.S. Coast Guard Inland Navigation Rules.  These requirements are not enforceable by OSHA.  If the CSHO observes violations of the warning signal when the dive location is on a vessel, no citation shall be issued.  However, the CSHO shall inform the employer of the violation(s) and recommend abatement(s).  The CSHO also shall note the incident on the OSHA-1 Form and notify the nearest U.S. Coast Guard Marine Safety Office of the violation(s).

                                                                              b.            The warning signal is a rigid replica of the international code Flag "A," and must be at least one meter in height (see Appendix F of this instruction).

 29 CFR 1910.422 Procedures during dive                              A.             

                                                       1.            29 CFR 1910.422(b) Water entry and exit.  A means capable of supporting the diver (such as an inwater stage or ladder) while entering or exiting the water is required.  If it is a fixed structure, such as a ladder, it must extend below the water sufficiently to allow adequate diver access and support.  The employer also must provide a means for assisting an injured diver from the water to the surface or into a diving bell (such as an inwater stage, stokes basket, or harness).

                                                       2.            29 CFR 1910.422(c) Communications.  An operational two-way voice communication system is required for communications between each surface-supplied air diver or mixed-gas diver and a member of the dive team at the dive location or in the diving bell (if a diving bell is provided or required).  Line-pull signals do not meet this requirement, except for the SCUBA-diving mode.  A two-way voice communication system is required for communications between the diving bell and the dive location.  Also, a two-way communication system (such as a cell phone, marine radio, or computer) must be available for obtaining emergency aid. 

                                                       3.            29 CFR 1910.422(d) Decompression tables.  This paragraph requires that decompression, repetitive, and no-decompression tables (as appropriate) be available at the dive location.  These tables serve as guides for determining decompression and no-decompression profiles for the diving operation.  The CSHO shall check that the decompression tables are available at the dive location (for standard air decompression tables refer to section V, paragraph H.3, of this instruction, U.S. Navy Diving Manual, Volume 2, "Air Decompression").

                                                       4.            29 CFR 1910.422(e) Dive profiles.  A written record called a depth-time profile (including any breathing-gas changes, when appropriate) must be maintained for each diver during the dive, including decompression.  This record aids the designated person-in-charge (or the dive-team member managing the decompression interval) in implementing the planned dive schedule and decompression interval, and making necessary adjustments in the decompression schedule if changes occur in planned bottom times or depths.  The dive profile information may be recorded by whatever means and in whatever form the employer prefers, provided that the information is maintained accurately and completely.

                                                       5.            29 CFR 1910.422(f) Hand-held power tools and equipment.

                                                                               a.            The standard does not require hand-held electric power tools used underwater to have a pressure-sensitive manual control switch.  However, when electrically powered hand-held tools are used underwater, and the source of power is supplied from the dive location or a diving bell, the hand-held power tool shall not be supplied with power until requested by the diver.  When the diver has finished work with the hand-held electric-power tool, the power to the tool will be de-energized from the dive location or the diving bell.

                                                                              b.            In addition to the requirements of 29 CFR 1910.422(f)(1) and (f)(2), all hand-held electric power tools and equipment must comply with 29 CFR 1910.303(b) and 29 CFR 1910.399.

Clarification of the term "approval" is given in 29 CFR 1910.303(a) as follows:  "The conductors and equipment required or permitted by this subpart shall be acceptable only if approved."

The term "acceptable" is defined under 29 CFR 1910.399 as follows:  "An installation or equipment is acceptable to the Assistant Secretary of Labor, and approved within the meaning of [29 CFR Part 1910, Subpart S - Electrical]."  An installation would be acceptable if it meets one of the following three conditions:

                        §   If it is accepted, or certified, or listed, or labeled, or otherwise determined to be safe by a nationally recognized testing laboratory [as defined by 29 CFR 1910.7].

                        §   With respect to an installation or equipment of a kind which no   nationally recognized testing laboratory accepts, certifies, lists, labels, or determines to be safe, if it is inspected or tested by another federal agency, or by a State, municipal, or other local authority responsible for enforcing occupational safety provisions.

                        §   With respect to custom-made equipment or related installations which are designed, fabricated for, and intended for use by a particular customer, if determined to be safe for its intended use by the manufacturer on the basis of test data which the employer keeps and makes available for inspection to the Assistant Secretary and [his/her] authorized representatives.

                                                       6.            29 CFR 1910.422(g) Welding and burning.

                                                                               a.            A current supply switch must be available to interrupt the current flow to the welding or burning electrode.  The switch shall be tended by a dive-team member in voice communication with the diver performing the welding or burning (see 29 CFR 1910.422(g)(1)(i)).  The disconnect switch must be in the open position unless the diver is actually welding or burning (see 29 CFR 1910.422(g)(1)(ii)).  The CSHO shall determine that the welding machine's frame is properly grounded and that cables, electrode holders and connections are insulated to prevent overheating or breakdown (see 29 CFR 1910.422(g)(2) and (g)(3)).  The employer must provide insulated gloves for the diver's protection (see 29 CFR 1910.422(g)(4)).

NOTE:  Personnel designated to operate electric cutting and welding equipment used in diving operations shall have experience or training in the safe use of this equipment (see 29 CFR 1910.410(a)(2)(i); welding and burning training violations will be cited under 29 CFR 1910.410). 

                                                                              b.            This standard does not place any restriction on the use of AC current or rectified AC current arc welding.

                                                                               c.            29 CFR 1910.422(g)(5).  "Closed compartments" as used in this paragraph, means any space that is enclosed by bulkheads and overheads (i.e., walls and ceilings), including large diameter pipes and other structures that, because of poor ventilation, could hold or contain a flammable gas or vapor.  Prior to hot work, the employer must remove from closed compartments all flammable gases and vapors by ventilating, flooding, or purging with an inert-gas that will not support combustion.  Venting alone is not sufficient unless it removes the flammable gases from the compartments.  Closed compartments, structures, and pipes already under flow, as in hot tapping operations, meet the requirement for being flooded.

WARNING:  A flooded compartment is not necessarily safe for cutting and welding.  During the cutting and welding process, oxygen, hydrogen (electrolysis), and other gases may collect in a closed compartment, if it is not properly vented (made gas free).  Should the diver cut or weld into the area where the gas collects, then a serious explosion can occur.  By properly venting the space, gas will not collect and the space will remain flooded.

                                                       7.            29 CFR 1910.422(h) Explosives.  Explosive charges are used to perform some types of underwater work, including demolition, sheet-pile cutting, cable cutting, and excavating.  Explosives suitable for underwater work include primacord, various gelatins (gels), plastic blocks, and some liquids.  Employers must comply with this provision, as well as the applicable requirements of 29 CFR 1910.109 and 29 CFR 1926.912, when handling, storing, and using explosives.  This provision requires divers to be out of the water when detonating an explosive or testing the electrical continuity of the explosive circuits. 

NOTE:  Only personnel who are properly trained or experienced shall handle explosives (see 29 CFR 1910.410(a)(1) and (a)(2)(i); explosive training violations will be cited under 29 CFR 1910.410).

                                                       8.            29 CFR 1910.422(i) Termination of dive.  This paragraph applies to all diving modes.  The designated person-in-charge is responsible for determining when a dive shall be terminated.  "Termination" means ending the working interval of a dive.  However, it may still be necessary to complete the decompression procedures.  The working interval of a dive must be terminated when:  the diver so requests; the diver fails to respond correctly to instructions from the dive team (indicating a possible disability of the diver or an equipment failure); communications with the diver are lost and cannot quickly be reestablished (either between the diver and the dive location or diving bell, or between the diver and the designated person-in-charge and the skipper of the support vessel for liveboating operations); or the diver begins to use the reserve breathing gas.  Any of these situations requires termination of the dive.  The decompression interval should not be omitted after termination of the dive if doing so would add to the diver's overall physical risk, unless the circumstances make inwater decompression impossible or present a greater physical risk to the diver.