Very grey area, some say the van should have floor vents not so much for Co2 but for any escaping gas, others say the cylinder should be in a metal box. When you phone the broker they generally haven't a clue what you're on about, mine only wanted to know the weight. Public liability insurance probably wouldn't be keen if they knew you ignited a boiler next to the commercial properties you were working on. I actually had a gas leak in my van - obviously the gas settled around the leisure battery complete with crocodile clips, one spark and the van would have gone up. You must remember to shut the gas off every
time you drive off too. I took mine out in the end just didn't seem right.
I used to buy my gas from a local marina - the supplier had completed a gas safety course - he wasn't impressed with what he saw.
Probably a good idea to carry a fire extinguisher too, I still have one on my tank frame.