- One cylinder containing air under pressure
- A harness to mount the cylinders on the, back of the person.
- A respiratory system which incorporates a means of reducing the pressure of the air from the cylinder and of supplying the wearer on demand with air according to his requirements, and
- A facemask attached to a demand valve, which maintains a positive pressure inside the mask at all times.
The arrangement of a typical apparatus is as follows:
The cylinders contain approximately 1240 litres of free air compressed to give approximately 31 minutes of full air usage time and 21 minutes of working duration under normal circumstances. Please note that the usage time greatly varies from person to person and the workload the person is performing.
