It is a cheat under Movie/Picture Cheats:
http://simswiki.info/wiki.php?title...p:Sims_2_Cheats
floatprop particleDensity [0-15]
Changes the amount of stink in green clouds in the game. 1 is default, 0 is no visible stink cloud at all. The game will allow very high numbers but there isn't really a visible difference past 10.
I have never tried it myself.