LogInIt appears that Valve actually built a whole AI system for different scents.
It appears that the original Half-Life was all about different odors. MarphitimusBlackimus broke down the game’s code to find out that characters don’t just remark on smells randomly — the studio actually built a whole AI system for it.
The game’s code knows three smell categories: meat, carcass, and garbage, though the studio only used two of these. This is why security guards will always comment on the odor of a nearby corpse. One funny fact – scientists won’t react! They have to, but that piece of the code is not working for some reason.
Bullsquids love smells — after a brief period they’ll start chowing down on nearby corpses. It is said that smells can get those creatures’ attention from far away, beyond a direct line of sight. After consuming a corpse, Bullsquids will seek out things that attract their olfactory glands, but the creatures won’t eat anymore.
One more fact – Half-Life corpses stop emitting odors after 30 seconds.