Gas leaks have become a less frequent occurrence with every year that passes, thanks to technological advancements and stricter safety restrictions. Even so, there is always a risk, however slight, of a fault or improper fitting leading to a leak, especially in the case of older appliances. Due to their rarity, you shouldn't feel as though you have to constantly worry about a leak but you should still know what to do if you smell gas.
The most apparent sign of a gas leak is being able to smell it. This only applies in the case of a gas leak and not a scentless and highly dangerous carbon monoxide leak. Carbon monoxide leaks are far more difficult to detect but there are some trusted methods, detailed in another article on this site. Other signs that there may be an issue with your gas appliances include soot around the appliance, cookers producing a yellow, flickering flame instead of a strong blue flame or your pilot light frequently going out. Even if you're unable to smell gas, there are physical symptoms that might indicate a gas leak. These include feeling lightheaded, dizzy or nauseous, suffering a persistent headache or a general sense of lethargy. If these symptoms appear while you're in your property and fade when you move outside, it's likely that you have either a gas or carbon monoxide leak and should take immediate action.
Your first priority should be to open any windows and doors in order to allow fresh air inside and lower the gas density. If you know where your gas mains tap is (usually close to your meter) and it's easily accessible, turn it off. You should then leave your property and call the 24 hour National Gas Emergencies helpline on 0800 111 999 and follow their advice. Do not use your mobile phone unless you're outside; electrical items can trigger a fire if a spark comes into contact with gas. The same applies to any other electrical devices in your property, such as light switches, and naked flames such as from matches or lighters. Once outside, do not re-enter your property until a gas engineer arrives and tells you it's safe. If you feel ill, go to your nearest GP or hospital as soon as possible and inform them that may have been exposed to gas or carbon monoxide.
Preventing a leak from occurring is always better than having to deal with one later. Always hire a registered Gas Safe engineer to install and test your gas appliances before using them. Having your appliances serviced by a trusted gas engineer, ideally annually, should mean any issues are addressed before they become significant. It's always a good idea to install a gas detector, as well as a carbon monoxide alarm (especially important due to it being otherwise undetectable and extremely dangerous). If you move into a rented property, it's the landlord's responsibility to ensure that everything is properly installed and serviced. You can ask them for a gas safety certificate to prove that they're fulfilling their obligations.