Switch to mobile site

Gas Safety

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

Create an Article


Combustion Process

Click to show/hide index

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

Complete Combustion

  • CH4+2O2=CO2+2H2O
< Go Back2013-03-12

Incomplete Combustion

  • CH4+1.5O2=CO+2H2O
  • CO - extremely toxic gas (0.4% in air is fatal)
  • Visual Signs :
    • Staining around the appliance (never acceptable)
    • Signs of sooting within the appliance (acceptable for live fuel burning)
    • Yellow flames within the appliance (acceptable for live fuel burning)
  • Causes of Incomplete Combustion :
    • Insufficient air for combustion
    • Overgassing
    • Undergassing
    • Flame impingement - flames from different parts of a burner disturb each other
    • Flame chilling
    • Vitiation - reduced level of oxygen in the combustion air
< Go Back2013-03-12

Air Requirements for Combustion

  • 1m3 of methane requires 2m3 of oxygen (10m3 of air)
  • produces 1m3 of carbon dioxide and 2m3 of water vapour
< Go Back2013-03-12

Flames and Burners

  • Post-Aerated Flames :
    • also known as a 'neat', 'luminous' or 'ragged' flame
    • air supplies the flame as it exits the burner
    • burn with incomplete combustion
    • used in a live fuel effect fires
  • Pre-Aerated Flames :
    • can be partially aerated or Bunsen burner type
    • 50% of the air for combustion is supplied prior to combustion
  • Pre-Mix Burners :
    • fan provides air under pressure
    • zero governor reduces the gas pressure to atmospheric pressure
< Go Back2013-03-12