7.(a) Describe TWO possible sources of contamination of compressed air used for breathing.(4)
(b) State THREE contaminants that may be found in compressed air, outlining the effect of the contaminant on the user when the compressed air is used for diving (SCUBA) purposes.(6)
(a) TWO possible sources of contamination of compressed air used for breathing (4 marks)
- Compressor suction intake located near exhaust outlets or fuel vapours (2 marks)
- If the compressor air intake is positioned close to engine exhausts, galley vents, or fuel vapour outlets, contaminants such as carbon monoxide, carbon dioxide, or hydrocarbons can be drawn into the compressor and passed into the breathing air.
- Lubricating oil carry-over from the compressor (2 marks)
- Oil used to lubricate the compressor can enter the compressed air system as oil vapour or mist, particularly if the filters or separators are faulty. This leads to contamination of the breathing air.
(b) THREE contaminants that may be found in compressed air, outlining their effects on the user when used for diving (SCUBA) purposes (6 marks)
- Carbon monoxide (CO)
- Effect: CO binds strongly with haemoglobin in the blood, preventing oxygen transport. This causes headache, dizziness, confusion, unconsciousness, or death even at low concentrations.
- Carbon dioxide (CO₂)
- Effect: Excess CO₂ in breathing air leads to hypercapnia (increased blood CO₂), causing shortness of breath, headache, and possible loss of consciousness under pressure.
- Oil vapour or mist
- Effect: Inhalation can cause irritation of the respiratory tract, nausea, and long-term lung damage. It may also form toxic gases when decomposed under high pressure and temperature.
Alternative acceptable contaminants: Water vapour (leading to corrosion and freezing in regulators) or particulate matter (causing irritation and filter blockage).