breathing apparatus, but also from other sources. Gloves and boots serve similar functions underwater to those they provide at the surface. Where the environment is contaminated by hazardous materials, the exposure suit, helmet, boots and gloves may be sealed together by watertight connections and the breathing gas exhaust system protected from water ingress by series non-return valve arrangements. Other more exotic personal protective equipment such as chain mail suits for protection against shark bites are occasionally used. Mitigation It is not usually possible to entirely eliminate risk to a diver, and where there is sufficient residual risk it is necessary to provide mitigation for the foreseeable consequences of an incident occurring. Emergency planning Professional diving teams may be legally obliged to make plans and provide equipment and personnel to manage reasonably foreseeable accidents. This can include a requirement for the contractor's operations manual to include instructions for the members of a dive team in the event of any of several classes of emergency, which may include managing an injured or unconscious diver underwater or at the surface, recovery of such diver from the water, provision of first aid, provision of recompression therapy in the case of decompression illness, communication with emergency services and the contracted diving medical practitioner on standby, decontaminating divers and emergency evacuation of the worksite. Specific checklists or flowcharts may be provided with emergency plans where they may be useful to ensure correct sequencing and that no critical stage is omitted. Technical divers, and in some circumstances, scientific divers, diving at remote locations, may arrange equipment for emergency in-water recompression. Recreational dive leaders such as divemasters and instructors may also be required to produce emergency plans for a dive site or area. The contents may vary depending on location and access to assistance, and would contain the information necessary to handle reasonably foreseeable emergencies. Content may include contact details for local emergency medical care, a casualty evacuation plan, how to arrange emergency recompression and other diving specific emergencies, and what assistance can be expected from the local emergency services. Recreational, and particularly technical divers, are recommended by certification agencies to have some form of emergency plan in case something goes wrong. The international organisation Divers Alert Network provides a hotline service giving advice on diving emergencies, and in the case of members, authorising and arranging emergency medical assistance and evacuation. Training to manage foreseeable incidents A large