Persons conducting a business or undertaking should ensure that all dives are planned conservatively and consistently to one set of recognised dive tables to minimise the risks of decompression illness.
Recognised dive tables include:
- DCIEM tables
- Buhlemann tables
- tables approved by a recreational dive training organisation
- dive computers used in accordance with the manufacturer's instructions.
Decompression management for high risk diving work must be undertaken in accordance with the requirements in AS/NZS 2299.1: 2015 Occupational diving operations – Standard operational practice.
Factors that may predispose a diver to developing decompression illness should be minimised as far as is reasonably practicable. These factors include:
- depth (generally, the deeper the dive, the greater the risk)
- poor physical condition (obesity, age)
- heavy physical exertion before, during or after a dive
- alcohol or some drugs (taken before or after a dive)
- previous incidences of decompression illness
- multiple ascent diving
- multiple dives over multiple days
- cold conditions
- prolonged hot showers after a dive. previous incidences of decompression illnesses
- depth – generally the deeper the dive the greater the risk, although decompression illness has occurred in divers diving to depths of less than 10 metres
- decompression stop diving
- carrying out free or buoyant ascent training
- prolonged dive times
- carbon dioxide excess
- increase in altitudes shortly after diving, for example, flying or travelling over mountains.
Flying after diving
The longer the period between diving and travelling to altitude, including flying, the less likely it is that decompression illness will occur.
Generally a 12 hour wait is advisable before any pressurised flights and a 24 hour wait if a diver has done multiple dives over several days or decompression stop diving. Specific advice is usually available from the recognised dive tables selected for the dive.
Maximum diving depths
Selecting the maximum depths for diving activities is important to minimise risks of decompression illness, gas toxicity and rescue of a diver in an emergency. Many dive qualifications, training programs and some medical certificates carry their own depth restrictions.
For high risk diving work, the advice regarding maximum depth in AS/NZS 2299.1: 2015 Occupational diving operations – Standard operational practice must be followed.
For general diving work, the recognised dive tables used will specify maximum depths. Divers who are competent under the requirements for incidental diving work and limited scientific diving work must only dive to a maximum depth of 30 metres without decompression stops.
For recreational diving the following maximum depths are advised:
- Dive workers - 40 metres
- Resort divers - 12 metres
- Entry level divers in training - 18 metres
- Entry level divers in training aged 10-11 - 12 metres
- Certificated divers – should not dive in excess of the depth to which they have been trained or have experience. A dive worker may not be able to assist a certificated diver beyond 40 metres.
- Decompression stop diving to 40 metres or less should only be undertaken by divers with decompression diving training; or 10 logged decompression dives; or who are accompanied by a trained dive worker.
- Decompression stop diving over 40 metres should only be undertaken by divers with decompression diving training.
Multiple ascents within a dive profile may increase the risk of decompression illness. Where it reasonably practicable, multiple ascents during a dive should be avoided.
Recreational dive workers should not teach more than one class of students in any 24 hour period to minimise their number of ascents.
Decompression stop diving
Dive profiles that require mandatory decompression stops create additional risks to divers of decompression illness, hypothermia and 'out of air' situations. In some situations it is difficult for divers to undertake in water decompression safely without surface support. Decompression stop diving should only be undertaken by divers undergoing specific training or who have been trained in decompression stop diving techniques.
For high risk diving work, the advice regarding decompression stop diving, including the provision or recompression chambers, in AS/NZS 2299.1: 2015 Occupational diving operations – Standard operational practice must be followed.
For general diving work, the recognised dive tables used will specify decompression stop requirements. Divers who are competent under the requirements for incidental diving work and limited scientific diving work must not undertake decompression stop diving.
For recreational technical diving, decompression stop diving should only be undertaken when:
- Emergency breathing gas is positioned at decompression stops
- A device for controlling position and ascent rates is used. For example shot lines and decompression bars.
- Dive plans are made and available at the surface. Each dive plan should include calculated gas consumption predictions for each diver to allow a safe amount of breathing gas and reserve for the dive. The dive supervisor should be aware of each dive plan.
- All divers should be equipped with a redundant gas breathing system and an alternate ascent system, for example a surface marker buoy.
Emergency plans must be made to identify divers showing signs or symptoms of decompression illness so that they can be given appropriate first aid. Advice from appropriate medical services should also be obtained so, if required, prompt evacuation to a recompression facility can be arranged.