The self-contained breathing apparatus comprises a face mask assembly, a frame (back plate) and harness assembly, an air cylinder and valve, a high pressure reducing valve, a warning whistle and a press니re gauge The face mask, which forms an air-tight seal around the face, has an exhalation valve, a demand valve, a voice diaphragm and some method of preventing misting. The demand valve permits the use of the equipment as a positive pressure set. This ensures that the air pressure inside the face mask is higher than atmospheric pressure and so any leaks in the seals are outwards. That is, smoke or foul air cannot be drawn into the mask. The back plate is attached to the harness and includes a method of securing the air cylinders. There may be provision to enable an alternative air supply to be connected.
Each cylinder is to contain not less than 1200 litres of fresh breathing air. The supply of air to the wearer is via an automatic regulator, but there will be a means of bypassing or over-riding the regulator to increase the volume of air available to the wearer should the need arise. It is required that spare charged breathing air cylinders are also carried.
A pressure gauge enables the wearer to ascertain the press니re of air remaining in the cylinder at any time.
A warning whistle indicates to the wearer that the cylinder capacity is low and that he should remove himself from any unsafe atmosphere.
A lifeline of flexible galvanised steel wire covered in plaited rope is also provided. The lifeline must be
at least 3m longer than is required to reach from the open deck in clean air to any part of the vessel.
The weight of the apparatus must not exceed 16kg (excluding the lifeline).
Every set of self-contained breathing apparatus must be provided with spares cylinders having a total free air capacity of 2400 litres. In practice this usually means that each set has two spare charged cylinders. There are however two exceptions:
i)in ships with five or more sets the total spare capacity (for the whole ship) need not exceed 9600 litres.
ii)if the ship is able to re-charge the air cylinders with suitable breathing air, then it is necessary to carry only 1200 litres of spare breathing air per set: however the total spare storage capacity of free air provided (for the whole ship) need not exceed 4800 litres.
Where ultra lightweight cylinders are carried there are restrictions concerning who may recharge the cylinders, the moisture content of the air used to recharge them, and the attention that must be given to the external cylinder protection and its condition.
Special air compressors intended solely for recharging compressed breathing air cylinders may be carried. They may be either portable or fixed. The air intakes must be sited so that the ingress of water or
noxious fumes is avoided, even in the most adverse circumstances. See the paragraph above concerning the restrictions placed on recharging ultra lightweight cylinders.
Inspection and maintenance of any self-contained breathing apparatus must be carried out by a competent person and strictly in accord with the manufacturers' instructions. The detailed instructions for each set will vary with the make and model.
After each use of a BA set it is necessary to ensure that it is stowed in a condition whereby it is ready again for immediate use. Follow the detailed instructions given by the manufacturer; they will generally include the following:
clean the set thoroughly
•clean the face mask and harness (this may be in warm soapy water)
•inspect the complete set for damage and any loose fittings
•fit a fully charged cylinder
•complete high pressure and low pressure tests q disinfect the facemask
•re-stow the equipment in a ready-to-use condition and complete all use and test records
Effective and efficient use of breathing apparatus may only be achieved by frequent regular training in its use and care. It is important that any crew member designed to wear the breathing apparatus is confident and comfortable with its use.