Gas Safety Check Chimneys and Flues

Chimneys and flues can come under the gas safety check. Many gas appliances have the combustion gases disposed of from the property to outside air either by a chimney or a flue. There are many different types of flue but in the main appliances that use a chimney or a flue can be classed as either:-

• Open Flue (e.g. Floor Mounted boiler)
• Flueless (e.g. Hob)
• Room Sealed (e.g. Modem boiler)
• In addition the flue can be Natural Draught or Fanned.

Open flue appliances take their combustion air from within the property and the waste gases are then discharged to outside up a chimney or up a flue. The correct operation of the natural draught chimney or flue will depend upon the rising air flow rising up the chimney or flue This occurs because hot gasses/air are less dense and will rise. This then pulls further air in below and the process continues.

The gas engineer will check that this process is occurring correctly by checking that the chimney or flue type is suitable and of the correct dimensions. The length of flue is important as the gases can cool and fall back into the appliance and room. This is known as spillage.

As an example when checking a gas fire that utilizes a chimney or flue while proforming a gas safety check the engineer will remove the appliance from the fireplace. The engineer will then check the chimney performance by burning a smoke pellet checking that the smoke flows correctly up and out of the chimney and that there is spillage back into the room. In addition the engineer should check that there are no breaks in the chimney either in rooms or in the attic.

This method will also be used where the appliance has a flue liner such as a back boiler.

When the appliance is running the engineer will do an additional check for spillage at the draught diverter on the appliance.

For flues with fanned appliances the process may be the same or slightly different depending upon the type of appliance.

The termination type and location of a chimney or flue must be correct. Only certain types of chimney termination are acceptable for gas appliances.

There are specific rules as to the location of a flue termination through a wall and the distances form certain features for example an opening window or door. The distances will vary depending upon whether the flue is natural or fanned draught.

Problems with flue termination are common. This is often as a result of some additional work done to the property after the flue was installed. The additional work is often done with little thought to the flue when either an extension is added or a window is located too close to the flue.

Failure for chimney and flue's to meet gas safety check may result in various levels of action depending upon the severity of the problem.

Continue reading about areas of inspection during a gas safety checks such as gas safety check combustion which is another aspect of the gas safety check.

MTS Heating Services provides the highest possible standards in gas safety checks adhering to chimney and flue inspections. Call today on 07971-784046 to arrange your safety check.