I'll get ya started.
1. Partial answer see following script. Put script in "Main" of door entity.
;Artificial Intelligence Script
;Header
desc = Use Door (Push Open auto Closes and locks)
;Triggers
:state=0:hudreset,hudx=50,hudy=90,hudimagefine=gamecoretextpressentertouse.tga,hudname=usedoorprompt,hudhide=1,hudmake=display,state=1
:state=1,plrdistwithin=45:hudshow=usedoorprompt,hudfadeout=usedoorprompt
:state=1,plrdistwithin=45,plrusingaction=1:state=2,setframe=0,sound=$0
:state=2:incframe=0
:state=2,frameatend=0:state=3,coloff
:state=3,plrdistfurther=45:state=4,sound=$1,colon
:state=4:decframe=0
:state=4,frameatstart=0:state=10,setframe=0
:state=10:none
;End of Script
Door will close and you won't be able to use it to get back out. It is locked up tight.
Fog can be used to emulate the gas. You won't be able to see it fall from the ceiling but you can make it slowly become thicker and more visible. You will need to somehow tell the player that this gas by using perhaps a hud. He can be like thinking to himself that this is gas.
I have not used "fog" yet so am not sure how to do this. But I am sure it can be done.
2. Fog is used here as well. Just place a hurt zone in this room. It can't just appear but you can adjust how slowly the player loses their health by tweaking the script that is in "Main" for hurt zone.
;Artificial Intelligence Script
;Header
desc = Plr Hurt In Zone with timer delay in milliseconds
;Triggers
:state=0:timerstart,state=1
:state=1,plrwithinzone=1,timergreater=1000:state=0,plraddhealth=-1
You can adjust the timergreater to be longer before health is depleted or faster. Too much faster you might as well not have the delay.
You can't get rid of the gas by getting rid of the fog. You can't make the trigger zones disappear but you can programmatically make sure the health is no longer being depleted. I'm not exactly sure of the sequence of events here but once you get out the window you are out of the trigger zone anyway and it takes care of itself except for maybe the fog I guess. The "hurt" will only take place
within the zone.
