Also how can I make a toxic gas zone? "trigger_hurt" with "def_damage" = "damage_noair_1" works in a same way like basic triger_hurt: hurt barks don't express suffocation - maybe some sort of water volume without movement restrictions?
Creating a vacuum is rather complicated. I also played around with it. These are my experiences:
I first tried to create a water entity that does not encompass the physics changes while under water, but am not firm enough in the soure code to find it. With simple definitions I could not do it.
The original doom has a couple of vacuum entities that are still present in TDM. However, Doom originally only used vacuum if you destroyed windows towards an evacuated area. I could recreate it for sepcific zones by creating a small, invisible room with a vacuum and giving it a door with a vacuum_trigger (not sure if this is the right name). Then I used the location system and created small areas out of visportals that triggered the door. Thus, when the player entered such a region, the door would get opened and the room flooded with vacuum. When the player left the region, the door would close and the vacuum would disappear. I have searched for easier ways to do this, but so far had no luck with that. Also, this method has some problems: the vacuum will expand through each open door, thus choking any AI, as long as the player is in the choking gas. Thus the player could kill any AI in the area by standing in teh choking gas with a couple of breath potions. Additionally, when the vacuum sets in, the sound that you hear will be of getting under water.