I have an 06 Daf XF spacecab 480, I have owned and driven from brand new but in the last month or two I can sometimes get a strong smell of gas in the cab,it might last a couple of minutes and then go away,sometimes it happens three or four times a day and NO IT’S NOT THAT KIND OF GAS children 
It happened yesteday as I was stopping to get out and when I walked past the front of the cab I could get the same strong smell of gas coming from under the grill.I carry a gas stove and a couple of spare canisters in the cab and thought they might be the cause but checked them and they seem fine,but now that I could smell it outside has me a little confused as to what it could be■■?
I’m thinking maybe the Air con■■?
Anyone come across this before?
I have no experience of this particular problem, but as I started to read your post I had two thoughts; firstly, cooking gas, which you’ve checked and ok’d. Secondly, air con. Try switching the air con on to check if it’s working, then lift the grill with it switched on and physically look and check for leaks. Other than that I’m afraid I can’t be of much help.
Get a pressure test on your air con.
How sure are you that the cooking gas is OK? If in doubt, bin it. I had one that was leaking and set fire to the cab when I lit it. Luckily I was on the ball and extinguished it fast.
Water leak?
I know when the heater matrix springs a leak it gets a tad smelly.
Thanks fellas,thinking it must be the Air con,if it was the cooking gas I wouldn’t have smelt it outside,and if it was a water leak it would have shown up by now,I’ll get the Air con checked,just thought it might have happened to someone on here before 