SPOILER. Cloud generation

[Sandman25]

I have just been frozen in Ice Volcano and I am trying to learn from the death. The map was ice_cave_caverns_02, it has the following code:
place_fog(_G, "freezing vapour", 10)

function place_fog(e, type, strength)
e.lua_marker("!", fog_machine { pow_max = strength, cloud_type = type,
delay_min = 50, delay_max = 300, size = 12,
start_clouds = 1, excl_rad = -1 } )
end
I found lm_fog.lua with description of the parameters but I am still not sure my understanding is correct so please confirm/clarify.
Every "big" cloud has a center where the big cloud appears every 5-30 turns and starts increasing into adjacent cells up to 12 cells total. Rate of spreading depends on cloud type (I guess it is below 1 turn for "freezing vapour"). Affected cells are random (eg. cloud may spread into one direction sometimes). Cloud in every cell will be present for 1-10 turns.
All that means there is no safe period when player can travel long way (7 cells for example) and be sure that freezing clouds will not be present at player location.
Correct?