CCN1 Gas Emergency Procedures

Question 1

What is the national gas emergency telephone number in Great Britain?

Accepted Answer

0800 111 999

Answer

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?

Accepted 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

Answer

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?

Accepted Answer

Electrical switches create sparks that can ignite the gas-air mixture, causing an explosion or fire

Answer

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?

Accepted Answer

Between 5% and 15% gas in air (the Lower Explosive Limit and Upper Explosive Limit)

Answer

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?

Accepted Answer

The isolation valve at or near the gas meter that can shut off the entire gas supply to the property in an emergency

Answer

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.

ACS CCN1 Practice Test

ACS CCN1 Practice Test

CCN1 Gas Emergency Procedures