CCN1 Gas Emergency Procedures — Questions and Answers
Question 1: What is the national gas emergency telephone number in Great Britain?
- 0800 111 999 (Correct answer)
- 999
- 0345 850 3025
- 0800 023 1110
Correct answer: 0800 111 999
0800 111 999 is the National Gas Emergency Service number, operated by Cadent (and other gas network operators). It is available 24 hours a day, 7 days a week, and is free to call.
Question 2: What is the correct immediate action if a gas smell is detected in a property?
- Do not operate any switches, open windows and doors, turn off the gas at the meter if safe, get everyone out, and call 0800 111 999 (Correct answer)
- Open windows only and call the landlord
- Turn on extraction fans to clear the gas
- Turn off appliances at their own controls and wait 30 minutes
Correct answer: Do not operate any switches, open windows and doors, turn off the gas at the meter if safe, get everyone out, and call 0800 111 999
On detecting a gas smell: do not operate any electrical switches (which can ignite gas), ventilate by opening windows and doors, turn off the gas at the emergency control valve (meter) if safe, evacuate, and call 0800 111 999 from outside.
Question 3: Why must electrical switches NOT be operated when a gas escape is suspected?
- Electrical switches create sparks that can ignite the gas-air mixture, causing an explosion or fire (Correct answer)
- Switches are gas-operated and will increase the flow
- Switches can interfere with the gas meter's safety shut-off
- Switches emit RF signals that affect gas sensors
Correct answer: Electrical switches create sparks that can ignite the gas-air mixture, causing an explosion or fire
Even low-energy electrical switches create small sparks when opened or closed. If gas has accumulated to within its flammable range (5-15% in air for natural gas), this spark can ignite the mixture, causing a fire or explosion.
Question 4: At what concentration in air does natural gas become explosive?
- Between 5% and 15% gas in air (the Lower Explosive Limit and Upper Explosive Limit) (Correct answer)
- At any detectable concentration
- Only above 50% concentration
- Only below 2% concentration
Correct answer: Between 5% and 15% gas in air (the Lower Explosive Limit and Upper Explosive Limit)
Natural gas (methane) has a flammable range of 5% to 15% by volume in air. Below 5% (LEL) there is insufficient gas to ignite; above 15% (UEL) there is insufficient air. Within this range, any ignition source can cause explosion.
Question 5: What is an 'Emergency Control Valve' (ECV) in a domestic gas installation?
- The isolation valve at or near the gas meter that can shut off the entire gas supply to the property in an emergency (Correct answer)
- The valve on an individual gas appliance
- A valve operated remotely by the gas transporter
- The valve between the meter and the service pipe
Correct answer: The isolation valve at or near the gas meter that can shut off the entire gas supply to the property in an emergency
The Emergency Control Valve (ECV) is located at or near the gas meter and allows the entire gas supply to the property to be isolated quickly in an emergency. All occupants and engineers should know its location.
Question 6: After a gas escape has been confirmed and the supply turned off, when may the gas supply be restored?
- Only after the source of the escape has been identified and repaired by a Gas Safe Registered engineer, and a tightness test confirms the installation is gas-tight (Correct answer)
- After 30 minutes to allow gas to disperse
- Immediately if the smell has cleared
- As soon as the occupant requests it
Correct answer: Only after the source of the escape has been identified and repaired by a Gas Safe Registered engineer, and a tightness test confirms the installation is gas-tight
Gas must not be restored until the escape source has been identified and repaired by a Gas Safe Registered engineer, and a tightness test confirms the installation is secure. Restoring gas without these steps risks further escape.
CCN1 Gas Emergency Procedures
What is the national gas emergency telephone number in Great Britain?