Whiff of gas when switching calor gas bottles via valve

[crappy]

I have two gas calor gas bottles outside for hob. They're connected via a transfer valve. Yesterday one run out (expected, roughly on-cue, 12 months per bottle).

When I switched from one to the other, I got got a whiff of gas. It was not continued.

Normal to have a whiff as you switch?

Transfer valve is around 24 years old.

 

[Fred Blogs]

I've used bottled calor gas for 15 years on 3 boats and now in calor gas heaters in my workshop. There has always been a whiff of gas when I have changed the bottles and when the bottle starts to run out I get a whiff then as well. I have always assumed this is normal and to be expected never had a problem over the years but I wouldn't go anywhere near a new bottle, or an old one for that matter, with a naked flame.