Posted By Bev William, I presume by gas that you mean natural gas, as supplied to our homes, etc. The hazards of damage to a gas pipe are an uncontrolled release of gas, potential of an explosion, and asphyxiation. Natural gas is mainly composed of methane, which if you look in EH-40 is an asphyxiant. I don't know what work it is that you have in mind, but no one should ever attempt to alter gas pipes unless they are a specialist company, with competent personnel, and specialist equipment. If you have damaged a gas pipe (containing natural gas), or have found one that is damaged, you should telephone Transco immediately on 0800 111 999. Keep everyone out of the area, turn the gas off if possible and ventilate the area if possible, do not operate anything electrical and do not smoke. If you are working in the vicinity of gas pipes on some unrelated work, you should consider whether your people will be working in a confined space and apply all the usual controls to that (permit to work system). You will need to test the atmosphere prior to entry (and during work) with a gas detector that detects low oxygen level and low explosion level and also the presence of methane. You can hire detectors but your people will need to know to use them. You may also need to consider the use of intrinsically safe tools, so that a spark will not be generated that could ignite any gas present. If you are going to excavate, you need to know the location of all underground services before you start. As mentioned above, you must not attempt to work on gas pipes unless you are a specialist company. If you are, you will also need to know if the pipe is live (ie there is gas in it) and if so, the pressure, as this will impact which fittings you can use. I hope this is of some help! Best wishes,