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Gas Safety

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

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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

Purging Volume

  • All air and gas mixtures have to be removed before commissioning an appliance
  • Inform the customer and put up notices if necessary
  • Open the ECV and note the meter
  • The following chart shows how much gas should be purged:
    Meter Pipework Purge Volumes

    E6, G4, U6
    Pipework ≤28mm

    U6, G4
    35mm ≤ pipework > 28mm
    0.01m3 + 1.5 x Vp*
    35mm ≤ pipework > 28
    0.0036m3 + 1.5 x Vp*
    G10, U16
    pipework ≤ 32mm
    0.03m3 + 1.5 x Vp*
    *Vp - volume of pipes and fittings
  • If the volume is 0.02m3 or less the gas can be purged into the building
    • if more than 0.02m3 a temporary burner must be installed
  • Open the appliance furthest from the meter
  • Establish a stable flame at each appliance
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When to carry out?

  • New installation
  • Alteration to, replacement of, or re-use exciting installations
  • New extensions to existing pipework
  • Where there has been a complete loss of pressure for any reason
  • Where there is the possibility of air being present in an installation
  • Where an installation is to be taken out of service temporary or permanently
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