Fire and smoke

[Mobhack]

But smoke from fire hexes (including burning wrecks) spreads downwind from that hex for the whole game.

The wind can be in any of the 6 hex directions - its random, set at the start of the game.

Smoke dissipation is determined by scenario visibility - it tends to clear faster on high visibility. Its also affected by wind strength - again, not directly addressable by a scenario designer, or known to the player directly but you know if its a windy day if smoke dissipates relatively quickly, and if it takes more than usual, then wind is low.

(Scenario visibility also affects LOS penetration into woods etc)