Just yesterday I went down to the boiler room in the cellar to get some frozen mash (I'm a lazy c*w) I could faintly smell gas, so I took a look at the boiler. Couldn't see any "on" green light, so thought it must have gone out, but the switch was on. Tried switching off and on again - no change. Still a smell of gas.
So I went out the cellar door, leaving it wide open in case of fumes, back indoors and phoned the gas leak number. A nice young man took the details, told me to open doors and windows, not to turn any switches on or off (too late) and to evacuate the property! - someone would be there within the hour. So I went next-door and begged to be allowed to sit there until someone came. Had a nice cup of jasmine tea, but the gas van arrived before I could finish it.
The engineer couldn't smell anything, but checked all around, told me the light WAS on but was very faint (invisible except in the dark) and went to check around the meter.
While he was gone, I had another sniff. Very faint, but more to my left that my right. Followed my nose till I reached the waste bin. Smell much stronger there. In it I found - two brussels sprouts which had fallen out of the freezer a few days ago and been lobbed in the bin. Engineer returned and could smell it now. Luckily he had a sense of humour (and stayed chatting for half an hour before departing. Well, it was Sunday and he was on overtime.