1910 Subpart T
Acfm means actual cubic feet per minute. It matters because air and gas flow rates for compressors, reserve systems, and breathing-gas calculations must be based on the actual cubic feet per minute delivered under operating conditions, not theoretical values (1910.402).
ASME Code or equivalent refers to the ASME Boiler and Pressure Vessel Code, Section VIII, or another code the employer can demonstrate is equally effective. An employer may use an equivalent code only if they can show it provides protection comparable to the ASME requirements for pressure vessels used in diving operations (1910.402).
ATA means atmosphere absolute — the total pressure at a location, including atmospheric pressure. Dive planners use ATA to calculate gas partial pressures and decompression schedules because breathing-gas behavior and gas loading depend on absolute pressure, not just gauge pressure (1910.402).
A Bell is an enclosed compartment, either pressurized (closed bell) or unpressurized (open bell), used to transport divers to/from the work area and may serve as a temporary refuge during operations. Practically, a bell can act as transfer equipment for deep or surface-supplied dives and as a pressurized refuge for decompression or emergency situations (1910.402).
Bottom time is the total elapsed minutes from when the diver leaves the surface on descent until the diver begins ascent. Employers should record bottom time precisely because it is a primary input for decompression planning and adherence to no-decompression limits or decompression tables (1910.402).
Bursting pressure is the pressure at which a pressure containment device would fail structurally. Equipment that holds gas under pressure (cylinders, chambers, volume tanks) must be designed and tested to have a bursting pressure well above the working pressure to prevent catastrophic failure (1910.402).
A Cylinder is a pressure vessel for the storage of gases. In diving, cylinders store breathing gases and must meet applicable design, inspection, and testing requirements to ensure safe storage and delivery of those gases (1910.402).
A Decompression chamber is a pressure vessel for human occupancy (surface chamber, closed bell, or deep diving system) used to decompress divers and treat decompression sickness. Employers should have a decompression chamber available when planned diving profiles or locations create a foreseeable need for surface decompression or treatment of decompression illness (1910.402).
Decompression sickness is a condition with various symptoms caused by gas bubbles in tissues after pressure reduction. If a diver shows symptoms, employers must provide immediate first aid and arrange prompt medical evaluation and hyperbaric treatment as appropriate; having trained personnel and a decompression chamber or access to one is critical (1910.402).
A Decompression table is a set of depth-time profiles for ascent rates and breathing mixtures to follow after a specific depth-time exposure. Employers must use appropriate decompression tables or equivalent procedures (e.g., approved diving tables or manuals) to plan ascents and prevent decompression sickness (1910.402).
Dive-guiding operations means leading groups of sports divers using SCUBA or similar apparatus to local undersea recreational sites. This differs from commercial diving because it centers on recreational guiding rather than industrial underwater work; employers should still ensure safe practices appropriate for guiding activities (1910.402).
A Dive location is the surface or vessel from which a diving operation is conducted. Identifying the dive location is important because it determines available support equipment, communications, emergency access, and how reserve breathing gas and decompression facilities are staged (1910.402).
Dive-location reserve breathing gas is an independent supply of air or mixed gas at the dive location sufficient to support divers during planned decompression. Employers must provide this independent reserve so divers can complete planned decompression or be supported during emergencies without relying on the primary supply (1910.402).
A Dive team includes divers and support employees involved in the diving operation, including the designated person-in-charge. The person-in-charge is essential for coordinating safety, communications, emergency response, and ensuring procedures and equipment meet requirements (1910.402).
A Diver is an employee working in water using underwater apparatus that supplies compressed breathing gas at ambient pressure. This definition applies to workers in commercial, scientific, or other occupational diving operations and determines who is covered by diving requirements (1910.402).
A Diver-carried reserve breathing gas is a supply carried by the diver sufficient, under standard conditions, to allow the diver to reach the surface, another gas source, or be reached by a standby diver. It must be sized and maintained so the diver can reliably return or wait for assistance in foreseeable situations (1910.402).
Diving mode is a type of diving requiring specific equipment, procedures, and techniques (SCUBA, surface-supplied air, or mixed gas). Employers must identify the diving mode because each mode has distinct hazards and required equipment, training, and emergency plans (1910.402).
Fsw stands for feet of seawater (or equivalent static pressure head). It is used to express depth-related pressure for decompression and gas planning; dive tables and decompression calculations often use Fsw as the depth unit (1910.402).
Heavy gear means diver-worn deep-sea dress including helmet, breastplate, dry suit, and weighted shoes. It is used in traditional heavy-suit diving operations where surface-supplied equipment and hard helmets are necessary for depth, endurance, or specific work tasks (1910.402).
Hyperbaric conditions are pressure conditions above surface pressure. They create hazards such as gas narcosis, oxygen toxicity, changes in gas solubility leading to decompression sickness, and require special equipment and procedures for safe operations (1910.402).
An Inwater stage is a suspended underwater platform that supports a diver in the water. It should be used when sustained underwater positioning is required for work tasks, providing rest, access, or a stable working platform (1910.402).
Liveboating is supporting a surface-supplied diver from a vessel that is underway. It raises safety issues like diver tether management, changing vessel motion, propeller hazards, and requires strict procedures and communication to protect the diver while the vessel is moving (1910.402).
Mixed-gas diving supplies the diver with a breathing gas other than air (e.g., helium-oxygen mixes). It is chosen to reduce nitrogen narcosis and manage oxygen partial pressures for deep dives where air would be unsafe or inadequate (1910.402).
No-decompression limits are depth-time limits from the Navy Diving Manual or equivalent that permit ascent without mandatory decompression stops. Dives planned within these limits allow direct ascent, but employers must still follow the specified tables or procedures and monitor repetitive-dive groups (1910.402).
Psi(g) means pounds per square inch (gauge) — pressure relative to atmospheric pressure. It is relevant because gas system pressures (cylinders, compressors, hoses) are measured in psi(g) for safe operation and equipment rating purposes (1910.402).
Recreational diving instruction means training students in recreational diving procedures and safe equipment use during dives, including use of SCUBA or semi-/closed-circuit apparatus. It covers classroom and in-water training for sport diving, not commercial underwater work (1910.402).
Scientific diving means diving done solely as part of scientific, research, or educational activities by employees whose only diving purpose is scientific tasks. It excludes typical commercial tasks such as placing/removing heavy objects, pipeline inspection, construction, demolition, cutting/welding, or using explosives (1910.402).
SCUBA diving is a diving mode independent of surface supply where the diver uses open-circuit self-contained underwater breathing apparatus. It requires specific training and procedures distinct from surface-supplied or mixed-gas operations (1910.402).
A Standby diver is a diver at the dive location available to assist a diver in the water. Their role is to be ready and equipped to perform an immediate rescue or assist in emergencies, following established emergency procedures (1910.402).
Surface-supplied air diving supplies the diver with compressed air from the dive location via a hose, unlike SCUBA which is independent of surface supply. Surface-supplied systems allow longer bottom times, communications, and sometimes hot-water or power through the umbilical, but require handling of surface equipment and tenders (1910.402).
A Treatment table is a depth-time and breathing-gas profile designed to treat decompression sickness. It is used by medical or diving personnel in a decompression chamber to recompress and treat affected divers according to established protocols (1910.402).
An Umbilical is the composite hose bundle between a dive location and a diver or bell that supplies breathing gas, communications, power, heat as appropriate, and includes a safety line. Employers must maintain umbilicals for reliability because they are critical life-support and communication links (1910.402).
A Volume tank is a pressure vessel connected to a compressor outlet used as an air reservoir. It smooths delivery, reduces pulsation, and provides reserve capacity for breathing-gas systems, improving stability and safety of the supply (1910.402).
Working pressure is the maximum pressure a pressure containment device may be exposed to under normal operating conditions. Employers must select equipment (cylinders, chambers, hoses) rated above the expected working pressure and maintain them to prevent overpressure incidents (1910.402).