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Gas Safety

Exam revision materials for Plumbing Level 2&3 and ACS Gas Safety test

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Carbon Monoxide Poisoning

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Safety Devices and Controls

Air/Gas ratio valves

Appliances Controls

Flame Supervision Devices FSD

Gas Controls

Gas Meter Controls

Safety Cut-off Devices

Spare Part Identification


Open-vented System


Gas Appliances

Ventilation Sizing

Unsafe Situations

Dealing with Unsafe Situations

Emergency Notices and Warning Labels

Gas Leak




Tightness Test

Gas Performance

Gas Rate

Heat Input

Gas Supply

Gas Meters

Gas Pipework

Gas Fittings and Pipes

Gas Supply


New Installation

Pipe Protection

Pipework Sizing

Chimney and Flue


Flue Construction

Flue Inspection and Testing

Flue Terminals

Flue Types


Carbon Monoxide Poisoning

Combustion Process

Natural Gas

Portable Combustion Gas Flue Analysers


Components and Safety Devices

Saturation of Haemoglobin with CO

  • 0-10% - no symptoms
  • 10-20% - tightness across the forehead
  • 20-30% - flushed skin, headache, breathlessness and palpitation on exertion, slight dizziness
  • 30-40% - severe headache, dizziness, nausea. Weakness of knees, irritability, impaired judgement. Possible collapse.
  • 40-50% - symptoms as above with increased respiration and pulse rates. Collapse on exertion.
  • 50-60% - loss of consciousness, coma.
  • 60-70% - coma, weakened heart and respiration
  • 70% and above - respiratory failure and death
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Volume of CO in the Air

  • 0.01% - tightness across the forehead with prolonged exposure
  • 0.03% - flushed skin, headache, breathlessness and palpitation on exertion, with 4 to 5 hours exposure
  • 0.05% - severe headache, nausea. Weakness of knees, irritability. Increased respiration and pulse rates and collapse within 4 to 5 hours exposure.
  • 0.4% - coma, weakened heart and respiration within a few mins.

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Carbon Monoxide Alarm

(~£13; BS EN 50291) - useful back-up precaution

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Combustion Process

Combustion Process
  • Complete Combustion - correct mixture (stoichiometric mixture) of gas and air
    • (1m3 of methane + 8m3 of nitrogen + 2m3 of oxygen) = (1m3 of carbon dioxide + 8m3 of nitrogen + 2m3 of water vapor)
  • Incomplete Combustion
    Incomplete combustion

  • Retention Flames
    Retention Flames
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