1st things 1st nobody is having a go at you, you posted a Q and different people have given their opinion, ok its not ideal that we all have different opinions, ie it should be black & white for everything but it isnt, coming on here will enhance your skill and knowledge, it does for me anyway, and i think im right in saying i have been doing gas 7 plumbing longer than you, sometimes when we have diff opinions we get a bit heated but at least it proves we care about what we do, and TBH it is usually just good banter between the troops, i suppose i must be one of the ones who said your guy was incompetant, what i meant was he is risking both you and him by being in a room with higher than safe levels, ok he was reentering the room to take the reading, but if above 30ppm the procedure is to abandon ship, so how many times did he reenter the room to see the reading climbing to 150ppm, and how dangerous is it to subject himself to such levels, i dont know the answer to that before you ask, but that means i would not have put you or i in that position, as soon as i saw a reading of 31ppm you and i would have been out