Some of the wording seems a little informal and clichéd: "a moment's notice", "hammering", "the subject's every move", "in time enough".
How about something like "at any time", something about "constant airflow", and "before he was killed" respectively. Is that a bit more clinical?
I like the picture.
I don't know what "at 30 degree angles from the center of the room" is supposed to signify. 30 degrees relative to what?
The room is 120 feet (40 m) high? What on earth for? This seems especially silly if the SCP is just a regular man-sized entity.
"As soon as any living man approaches:" I'd suggest "human" for "living man." I assume the SCP works on women too (which the original phrasing leaves ambiguous), since the initial case resulted in the SCP killing a woman, and "living" isn't really necessary, since dead humans don't do a lot of approaching, as a rule.
Fans wouldn't actually disperse mist from the guy, if he's in an enclosed space. They'd just blow the mist around the room. To disperse, the mist would need a way to leave, like a vent or something, or else it would start to condense on walls, cameras, and any other objects in the room. (Considering how it works, you probably would want an unventilated chamber for this SCP, which should be noted in the containment procedures. Might need to do something about condensation water, too, or else you'll need a 20 x 20 x 40 m aquarium.)
Does "it is able to do this even when inside its cell" mean that the SCP can take people even when they're not in the cell with it, so long as they're within the radius of its influence?
I do not like the incident log at all.
Why not just have the fans going all the time? What's the advantage in only activating them a few seconds after something horrible starts happening?
"When the creature itself is not surrounded by SCP-1198-1 it appears harmless and is in a semi-paralyzed state, except for its head." Well, it may appear harmless, but the person writing the report knows it isn't, and the person reading the report knows it isn't, so I think you should skip the harmless part. "Semi-paralyzed" isn't very well-defined, either. I mean, you say it can move its head, and that the rest of it is semi-paralyzed. So what other parts move, besides the head?
Okay, that really helps! With the fog I was thinking that that for some strange reason he can only form the mist when it is completely still. Because to my knowledge, not a lot of fog forms in really windy places. Kind of a personification of nature, if you will.