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Gas Safety

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

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Chimney and Flue

Flue Inspection and Testing

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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

Flue Inspection and Testing

  • clips are not more than 1.8m apart
  • bends are not more than 45° (30° - for pre-cast flue)
  • Flue-flow testing using a Smoke Pellet (5m3 of smoke within 30 sec)
  • Spillage testing using Smoke Matches
    Characteristic Natural gas Propane Butane
    Specific gravity 0.6 1.5 2.0
    Calorific value 39MJ/m3 93MJ/m3 122MJ/m3
    Stoichiometric air requirements 10:1 24:1 30:1
    Supply pressure 21mbar 37mbar 28mbar
    Flammability limits 5-15% 2-10% 2-9%
    Flame speed 0.36m/sec 0.46m/sec 0.45m/sec
    Ignition temperature 704°C 530°C 408°C
    Flame temperature 1930°C 1980°C 1996°C
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