HAZMAT diving is widely regarded as the most dangerous branch of the commercial diving industry, employing highly skilled and experienced staff.
Typical work involves diving into raw sewage or dangerous chemicals, such as paper pulp, liquid cement, or oil sludge. This causes special requirements:
- The divers need to be vaccinated against diseases such as hepatitis and tetanus.
- The dive company needs to have specialist plans in place for decontamination of the diver and equipment after a dive.
- A way to recover the diver if something goes wrong.
- The diver's weighting may need to be adjusted, if he is diving in a liquid whose density is much different from the density of water.
The main tasks a diver can be found to be doing include:
- Essential maintenance of underwater valves and sluice gates.
- Repairing damaged pipelines.
- Pollution control work to contain, control, and clean up after a pollution incident.
- Some divers are required to dive into landfill sites to maintain the pumping equipment, vital in preventing landfill sites from filling up with rainwater and contaminating the water table.
- Welding inside live sewers or working in septic tanks.
- Miscellaneous repairs and finding lost objects.
- Finding bodies.
Sewer diving is often considered the most dangerous of all the HAZMAT jobs due to the diseases contained in raw sewage and because syringes and glass find their way into the raw sewage, creating risks of contracting diseases.
Divers working in an environment harmful to their health will always wear a full drysuit with thick gloves which are attached directly to the suit, the helmet and boots will also attach directly to the drysuit, this allows the gloves, boots, suit and helmet to be pressured in order to prevent ingress of liquid should a puncture occur. Normally, to achieve this, a diver will use a free flow diving helmet which continually supplies enough air for the diver to breathe plus an additional amount to pressurise the suit; a free flow helmet has a much lower chance of leakage through the exhaust valve compared with a demand helmet where the exhaust valve is dormant during the inhalation stage of the diver breathing.
The drysuit will be made from a material resistant to whatever hazard the diver faces: normally the diver wears a vulcanised rubber drysuit, but occasionally a neoprene or tri-laminate suit is needed. Often, a diver will wear extra protection over their drysuit to decrease the chance of a puncture: leather, PVC, and nylon coveralls are used for this purpose.
In such diving light is often very scarce, so most such divers rely on touch to guide them, and are usually connected via rope to the surface.
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Nuclear diving
Nuclear diving is similar to HAZMAT diving; the difference is the exposure to radiation instead of a water borne contaminant. To this end, different precautions are required for nuclear diving, mainly, equipment which will not absorb radiation and pose a disposal problem after several dives.
Heat stress can also be a danger for the diver, in which case a cold water suit may be used: the cold water suit is a special canvas coverall which floods the outside of the diver's drysuit with chilled water, countering the dangerously high ambient water temperature. A dosimeter is used to ensure that the diver does not receive a dangerous dose of radiation during the dive, assisting in calculating the maximum length of the dive. In addition the dosimeter can also be used to find radiation hotspots, which can indicate areas in need of repair.
Scientific diving
Scientific diving is the use of diving techniques by scientists to study underwater what would normally be studied by scientists on land. Scientific divers are normally qualified scientists first and divers second, who use diving equipment and techniques as their way to get to the location of their fieldwork. Underwater archeology, marine biology and geology are examples of sciences pursued underwater. Some scientific diving is carried out by universities in support of undergraduate or postgraduate research programs. In the United States scientific diving is permitted by the Occupational Safety and Health Administration to operate under an alternative consensual standard of practice that is maintained by the American Academy of Underwater Sciences. The perspectives on the regulation of scientific diving of two founders of the American Academy of Underwater Sciences: Lloyd Austin and Phil Sharkey can be found in OCEANS Volume: 15, pp460- 463.
To be able to avail itself of the Scientific Diving Exemption the institution under whose auspices the work is carried out must meet four tests:
- 1. The Diving Control Board consisting of a majority of active scientific divers must have autonomous and absolute authority over the scientific diving program's operations.
- 2. The purpose of all projects using scientific diving is the advancement of science; therefore, information and data resulting from the project are non-proprietary.
- 3. The tasks of a scientific diver are those of an observer and data gatherer. Construction and trouble-shooting tasks traditionally associated with commercial diving are not included within scientific diving.
- 4. Scientific divers, based on the nature of their activities, must use scientific expertise in studying the underwater environment and, therefore, are scientists or scientists in training.
Government bodies such as the United States Environmental Protection Agency and the UK Environment Agency carry out scientific diving to recover samples of water, marine organisms and sea, lake or riverbed material to examine for signs of pollution.
Equipment used varies widely in this field, but surface supplied equipment though quite uncommon in the UK is growing in popularity in the U.S. The short number of dives made by scientific divers in normally quite shallow water, and the UK governmental regulations that make surface supplied equipment cumbersome, when combined with a need for easy transportation make surface supplied gear uneconomic and undesirable for UK scientists to use.
The two standard references for Scientific Diving Operations are:
Flemming, N. C., Ed.; Max, M. D. (Ed) Code of Practice for Scientific Diving: Principles for the Safe Practice of Scientific Diving in Different Environments. UNESCO Technical Papers in Marine Science 53.
Joiner James T. (ed), NOAA Diving Manual: Diving for Science and Technology, Fourth Edition, 2001, U.S.Department of Commerce, National Technical Information Service, (ISBN: 0941332705)
Media diving
Media Diving is a term that covers underwater photography and underwater filming. Media Diving is often carried out in support of television documentaries, such as the BBC series Planet Earth or Hollywood blockbusters, with feature films such as Titanic and The Perfect Storm featuring underwater photography or footage. Media divers are normally highly trained camera operators who use diving as a method to reach their workplace, although some underwater photographers may start as recreational divers and move on to make a living from their hobby.
Equipment in this field is varied with SCUBA and surface supplied equipment used, depending on requirements, but rebreathers are often used for wildlife related work as they are normally quiet, release few or no bubbles and allow the diver a lengthy bottom time with a reduced risk of frightening off the subject at hand.
Military and naval diving
Military diving covers all types of diving carried out by military personnel. There are a number of different specialisations for a military diver to choose, some depend on which branch of the military they've joined or where the military needs more divers. Typical offensive activities include underwater demolition, infiltration and sabotage, this being the type of work elite regiments such as the UK Special Boat Service or the USA Navy Seals carry out. Defensive activities are centered around countering the threat of enemy special forces and enemy anti-shipping measures, and typically involve defusing mines, searching for explosive devices attached to the hulls of ships, and locating enemy frogmen in the water.
Military divers need equipment which hides their position and prevents explosives from being set-off, and to this end, they use rebreathers which produce few or no bubbles on the surface, and which contain no magnetic components, this continues down to the design of their diving suit, which will normally have a non-magnetic zip, and the face-mask may be fitted with special anti-reflective glass. Some navies have gone further and given their divers special contact lenses instead of large face-masks to cut down on the risk of a reflection.
Naval diving is the military term for commercial diving, and is drastically different to military diving. Naval divers work to support maintenance and repair operations on ships and military installations. Typical tasks include changing propellers or fitting replacement anodes. Naval divers may also work to recover downed aircraft, submarines, missiles and other military hardware. Their equipment is derived from commercially available equipment, with the US Navy using versions of the Kirby Morgan helmets and full-face masks amongst other equipment.
Experimental diving, is conducted by the US Navy's Experimental Diving Unit (NEDU) and involves meeting military needs through the research and development of diving practices and diving equipment, testing new types equipment and finding new and safer ways to perform dives and related activities. The US NEDU was responsible for much of the early experimental diving work to calculate decompression tables and has since worked on such developments as heated diving suits powered by radioactive isotopes and mixed gas diving equipment, while the British equivalent (The Admiralty Experimental Diving Unit) perfected the Mark 10 submarine escape suits utilized by both the Royal Navy and the US Navy.[2]
Police diving
Police divers are normally police officers who have been trained in the use of diving techniques to recover evidence and occasionally bodies from rivers, canals and the sea. They may also be employed in searching shipping for contraband substances fitted to the outside of hulls to avoid detection. The equipment they use depends on requirements, but the requirement for communications at some sites does often require the use of full-face masks with communication equipment, either with SCUBA or surface supplied equipment.
Dive instruction
There are two differing types of dive instructor. Some train recreational divers while others train professional divers.
Recreational dive instructors differ from other types of professional divers as they normally don't require a professional level qualification, but a relevant recreational qualification from a recognised training agency such as NAUI, PADI, SSI, YMCA or BSAC, which permits them to teach. Dive instructors teach a wide variety of skills from entry-level diver training for beginners, to diver rescue for intermediate level divers and technical diving for more experienced divers. They often operate from dedicated dive centres at coastal sites or through hotels in popular holiday resorts or simply from local swimming pools. Initial training is carried out mainly on conventional SCUBA equipment but with the increasing use of rebreathers, their use is also taught. Not all dive instructors are professionals; many instructors are amateurs with careers outside the diving industry.
Commercial dive instructors normally require professional diving qualifications. They typically teach trainee commercial divers how to operate types of diving equipment and typical underwater tools they will use in the course of their work. Commercial dive instructors will use similar equipment to commercial divers in the course of their work.
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