In T192510#2827759, @Caius-Corsades wrote:

Yes, I think it's something like that. It happened to me 5 or 6 times on the official server. I was in a car, entering a clear town, and then suddenly the mist appeared. I think that if you don't receive the data for the event starting, you don't see the mist — just like when you're too far during a bombing, or after disconnecting and reconnecting.

Same problem here. It’s been a few days we have the same problem. We ran into two gas zones with no visual gas. Just happened to me in Novy, and last time was on the military zone south Dubrovka. I recorded the even if necessary. Both times, it was a dynamic gas event we didn’t hear, no gas bomb sound. When we hear the sound, the gas is visible. Last one in Novy was interesting cause I heard the event, and I saw the gas first. I chose to wait for the gas to disappear and logged off my server. When I logged back 20 minutes later, no gas. I thought is was gone so I entendes Novy and got sick immediately - playing on Xbox