Personally I don't see why you think one is safer than the other? They both have their individual hazards but both need similar controls. If I was responsible for a construction site where hot work involving either substance I would instruct the user/s to make sure the cylinders are taken off site at the end of each day. They should take their precautions using their own equipment (blankets, extinguishers etc.) and request a fresh hot work permit each day prior to starting work. (Further requirements as well as per the HWP rules). The main difference I can see is if there is a fire and acetylene is on the premises the FRS will introduce a 200m (or larger) exclusion zone around the site so if there is a fire and the cylinders can be removed when the operatives evacuate, that is what should happen, get it written into the evacuation Plan.

RT, for me there's a couple of key differences in the types of gas that may guyide your decision. The first one is that propane is heavier than air and as a result, if it leaks, will effectively 'pool' in depressions in the ground. Acetylene on the other hand is slightly lighter than air and will tend to disipate if it leaks. The second difference is (to my mind at least), as already stated, the exclusion zone placed around acetylene in the event of a fire (200m) and this may be the driver for your decision. I had to make a decision of a similar nature a couple of years ago relating to how we use and store acetylene on one of our inner city key sites. Whilst the safety risk may not be significantly different in real terms the guidance of a fire engineer led me to decide that we couldn't afford to store acetylene at a location that had several major roads and mainline railway within 200m of the site. Whilst the storage was compliant the knock on risk in the event a fire did occur was too high for my liking. As a result we switched to propane with an option to get small quantities of acetylene when necessary. The overall performance between propane and acetylene shouldn't be a great issue, with the right setup and the right 'welder' they'll do the job as effectively whichever type of gas is used.

As a firefighter from 1968 to 1991 I attended many incidents involving cylinders, some of which resulted in the BLEVE mentioned by biker 1, that has jogged my memory. I also trained at the fire service college on a number of courses where we learned the hazards involved with compressed gas cylinders, and exercises with real compressed gas cylinder fires at which we were taught the correct procedures for firefighting such incidents. Funny to say the Propane cylinder fires were always worse and it it those that resulted in exploding cylinders although acetylene cannot be discounted as a very hazardous material and a cylinder rupture can result from excessing heating of either cylinder.

A few things from an engineering process standpoint. There are a few things that can ONLY be done with OA, OP will just no cut it. The removal of the DA from site each night is a very good idea, HOWEVER, it MUST be transported in an open vehicle, & MUST be transported & stored upright, unless, after it has been laid down, it is left to stand for the time specified by the cylinder supplier before it is used, TBH, not practical. The other replies are all basically sound. First port of call is to look at the processes that are being undertaken, heating & cutting only, for general construction industry, OP, silver soldering & welding probably OA. Brazing or braze welding, could be a close call, and silver soldering is borderline really too, but my preference would be for OA. DA is just that dissolved in Acetone, the absorbent material used to be "Kapok" (spelling) IIRC, though it has been a long time. Not sure what it is now, there is a pdf on the Air Products website that explains a little more. TBH, both are quite safe in competent use. Check valves torch end, flashback arrestors at the reg, quality kit, in good condition, inspected & checked by competent people before each use, I don't mean every 5 minutes or every time it is lit, I mean every time it is set up and dismantled. Leak checked correctly on assembly before use. Competent users, same people as the inspectors, as they should be competent to do both else they are not competent to do either. Oil & grease free setup. Regulators serviced / checked in accordance with manufacturers instructions. Suitable precautions during use, including serious thought about the positioning of the cylinders. I torched a 1/2 tonne piece off a machine as an apprentice, in a large RORO skip, but the back door had not been secured by the driver, the piece of cast came straight out of the skip and severed both lines, torch went out virtually instantly. Cylinders were safely secured, the buggy was about 1/2T itself! Apart from the row, no real issues. The lump of cast was cold, no reason for it to ignite the gasses, and we were outside. I jumped down and closed off the cylinder valves just like I was taught. DA first as that is where the valve key was, just like I was taught! This was a while ago! Anyway I digress. Oxy can also be dangerous, a full Oxy cylinder on its side unsecured, if it should have the valve assembly knocked off will go off like a rocket. So on to my next point, cylinders secured in the upright position. I'm going on a bit now, time to stop! HTH. Paul

RTrueman, As an ex-engineer I have some considerable experience with welding and cutting using both oxy-acetylene and oxy-lpg so I know that sometimes lpg just isn't up to the task. In addition to the really sensible comments above, you may wish to look at the British Compressed Gasses Association (BCGA) website which has a lot of information on risks, handling and using various gasses. They also have some generic risk assessments for transportation, handling and use of oxy-acetylene which are free to download. Regards Carl

Thanks all for your comments - all very helpful and informative. We haven't made any final decision yet, but as an example to put things into context, I had an M&E electrician using an oxy acetylene set to warm a duct fitting "because it is faster than using the blowtorch!" I will take all of these positive comments on board when finalising our decision on the matter. Rog T

Hi i have a copule of documents / processes, part borrowed and available for all to use. Send an email to competentadvice@groveservices.co.uk - Jeff Manion. There is no commercial gain to send these. Jeff Manion

If you request contractors to conform to a site rule that is there for good operational reasons and they disobey -what do you do? Construction sites are rarely in isolation - they need to take into account client's adjacent operations and neighbours too.