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Gas Safety

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

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Gas Appliances

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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

Adventitious Ventilation

  • natural ventilation sufficient for complete combustion of 7kW appliance
  • equals to 35cm2 of ventilation
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Air Vents

  • Must be permanent
  • Should be non-closable
  • Holes must be in between 5mm and 10mm
    • the size is actual free area
  • Corrosion resistant and stable
  • Inner and outer grills must be connected by a liner to bridge the cavity
  • Minimum separation distance between Air Vents and Flue Terminal applied
  • Types of air vent
    • Circular wall air vent
    • Floor vent
    • Door vent
    • Plastic inner wall or vent
    • Rectangular air vent
    • Air brick
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Vents in Series

ventilation in series
  • Two vents in series
    • Vent 1 (Outside vent) = Vent 2
  • Three or more vents in series
    • Vent 1 (Outside vent) = 1.5 Vent 2 = 1.5 Vent 3 = ...
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Vents for Flueless Appliances

  • Must be in a room with an openable window
  • Any ventilation must be directly to outside - not another room
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Vents for Open-flued Appliances

ventilation for Open-flued Appliances
  • Must be a permanent supply of air to that room
  • Not allowed to fit in Shower or Bathrooms
  • On range rated appliances ventilation is based on the maximum input
  • In a room
    • 5cm2 for each kW above 7kW
  • In a compartment
    • Compartment label should be fixed
    • No allowance is made for adventitious air
    • the door will not open into a Bedroom or Bed-sitting Room if appliance heat input is over 12.7kW net (14kW gross) or Air Sensing Device ASD is not fitted
    • Maximum height is 450mm for air inlet vent from the floor level
    • Air supplied from outside - 5cm2/kW (high level) and 10cm2/kW (low level)
    • Air supplied from a room- 10cm2/kW (high level) and 20cm2/kW (low level)
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Vents for Room-sealed Appliances

Ventilation for Room-sealed Appliances
  • In a room - no vent required
  • In a compartment:
    • Air supplied from outside - 5cm2/kW for both at high and low level
    • Air supplied from a room - 10cm2/kW for both at high and low level

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Gas Pipework Ventilation

  • Ventilated Duct
    Ventilated Duct
  • Enclosed Area
    Gas Pipework Ventilationin an Enclosed Area
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