Many homes in the UK have a gas supply for the purpose of heating and cooking. The gas supply may be fed directly from pipes coming from the street outside your home and enter via a gas meter. Alternatively, you may buy your gas in bulk in a liquefied form and store it outside in a special holding tank until it is required, when it is drawn off automatically as it is converted to its gaseous form. These two methods of gas supply are essentially the same to you, the consumer: you open a pipe and gas comes out.
The two gas types are:
C
C natural gas – fed directly from a pipe in the street C
C liquefied petroleum gas (LPG) – supplied in gas cylinders or bulk-purchased.
Both types of gas burn in the presence of oxygen, producing a blue flame. They both have a distinctive smell – not a true property of the gas but a ‘stenching agent’ added at the production plant, so that it is easy to recognize should there be a leak.
The two gases have slightly different characteristics. One of the key differences is the way that they react on leaving the pipe.
Natural gas is lighter than air, so it will rise upwards and be readily dispersed into the environment. LPG, on the other hand, is heavier than air and sinks down towards the ground and so is not as easily dispersed, often gathering in low-lying pockets such as basements. LPG gas leaking from a pipe drops around your feet and is less easily smelled, which results in it rapidly accumulating undetected.
The gas pipework for a natural gas installation is fed through a gas meter, purely for billing purposes. Obviously, this is not required when the gas is bulk-purchased.
It is important to note the location of the emergency control valve at the point of entry to the building. This should be accessible at all times so that, if required, the supply can be shut off very quickly. From this point the gas pipe is run to all the appliances requiring a gas supply (Figure 2.1).
Within a gas appliance, the gas is regulated and passed through a fine injector in order to allow the correct proportion of gas and air to mix within the combustion chamber where the fuel is burned. The appliance has many safety measures to ensure that gas will not flow through the appliance until it is required and that it can be burned safely. Due to the potential danger of incorrectly installed gas fittings, the installation of pipework and the provision for its use fall under very strict regulations. It is not illegal to work on your own gas installation pipework or appliances on a DIY basis, but unless you are absolutely certain of what you are doing you would be ill advised to touch anything. Gas installers are trained and assessed to ensure their competency to carry out gas installation work; when any gas work is carried out within your home you must ask to see the engineer’s gas registration card, identifying what areas of gas work they are allowed to undertake (see Appendix 1: Legislation).
emergency control valve to close off the supply A
15mm
15mm 22mm
22mm cooker
fire boiler
meter
Figure 2.1 Layout of a typical gas installation
Remember this
Never employ someone to undertake any form of gas service, installation or repair in your home without first confirming that the operative is registered with the Gas Safe Register. Your safety – and the validity of your home insurance – may depend upon it if something does go wrong. Confirm an operative’s Gas Safe Register details by phoning 0800 408 5500.
A leak from a water-filled installation can cause a great deal of damage but it rarely poses any real danger. On the other hand, a gas leak within a property is highly dangerous. When gas is burned, it is converted to water vapour and carbon dioxide, both of which are harmless gases, being present in the atmosphere and within the air we breathe. However, if for some reason insufficient oxygen is available in the air used for the combustion process, incomplete combustion can occur and as a result carbon monoxide is produced.
CARBON MONOXIDE (CO)
Every year, carbon monoxide gas poisoning claims the lives of around 30 people in the UK. The fuels we burn – including coal, wood, oil and gas – are hydrocarbons, which are made up of hydrogen and carbon in various proportions. Both of these elements can burn in the presence of oxygen and, if completely consumed, are converted to harmless carbon dioxide (CO2) and water vapour (H2O). However, if insufficient oxygen is available to support the combustion process, carbon monoxide (CO) may be produced because the carbon is not fully
converted to CO2.
Carbon monoxide does not have an odour and therefore cannot easily be detected. An appliance can discharge small quantities of this combustion product into the home without detection.
Look at Table 2.1. It lists the common symptoms of carbon monoxide poisoning that are often simply attributed to stress or tiredness from overwork. If in doubt, have your fuel-burning appliances checked.
Warning: Very small proportions of carbon monoxide in a room can prove fatal very quickly.
Remember this
Carbon monoxide (CO) gas is the result of incomplete combustion. Fuel requires oxygen to burn, and if insufficient oxygen is reaching the fuel, combustion will still occur but the fuel will not be completely consumed and CO will be given off. Where an appliance has an air supply via a grille, do not block it.