Hi there!
There have been a few times I have walked into an area that looks completely safe one step and the next I'm in a toxic gas cloud from a gas bombardment event. Stepping back there is no gas visible. It is only visible inside the gas cloud. On foot this is a minor annoyance as you can easily retreat on time before being poisoned by the gas. Unfortunately I have just had this experience but whilst going at roughly 50kph in a car which I crashed in the momentary panic so I was unable to retreat in time and died shortly after. There was absolutely no warning of the gas, no explosion from the bombardment. No glass from a pox grenade broke and a grenade launcher was not fired. I was just simply and suddenly enveloped by gas with zero warning.
Other players on the DayZ subreddit have mentioned similar situations also.
This is not always the case however, I can still hear bombardments in the distance and recently I was heading to a location and just before the I got there it was it by gas (loud explosion and visible gas) I stopped and moved away to observe the gas before I tried to loot an area not covered by it however the gas was white, not green which I took to be a case of a very minor error had occurred server side when loading the gas textures.
Thank you for taking the time to read the bug report and I wish you luck with hopefully fixing it!
Regards,
BaldMoustache