I take it your a bit new to coding?
No worries you will get the hang of it in no time! I created a script for you, the only problem is that the health hud and other huds are still behind the gas mask hud. I found a command called 'hudlayer=' but I had no luck with that or any other commands I tried. The problem is they're preloaded into the level so I doubt you can rearrange them. I would suggest making your hud semi/transparent in those spots so that player could still see the huds.
Ok so I made some changes. I didnt know why you use "scancodekeypressed=0" if thats not a press able key so I replaced it with key release. Also I didnt understand if you wanted gas mask only usable in a trigger zone? My script will show text when you enter the trigger zone allowing you to equip the gas mask (hud), you can then take it off by pressing the 'G' key again even when you are no longer in the trigger zone. I also added a play sound command so put a nice audio of a mask being equipped in the trigger zone properties and your good to go.
;Artificial Intelligence Script
;By 2S!K Productions
;Header
desc = showsmask
;Text
:state=0:hudreset,hudx=50,hudy=90,hudsize=22,hudfont=arial,hudtext= 'G' to equip gas mask,hudname=text,hudhide=1,hudmake=display
:state=2,plrwithinzone=1:hudshow=text
:state=2,plrwithinzone=0:hudunshow=text
;Triggers
:state=0,plrwithinzone=1:state=1
:state=1:hudreset,hudx=50,hudy=50,hudimagefine=gamecore\huds\Gmask.dds,hudname=Gmask,hudhide=1,hudmake=display,state=2
:state=2,plrwithinzone=1,keypressed=34 1:hudunshow=text,state=3,sound=$0,hudshow=Gmask,state=4
:state=4,keypressed=34 0:state=5
:state=5,keypressed=34 1:hudunshow=Gmask,sound=$0,state=6
:state=6,keypressed=34 0:state=0
;End of Script
As always, Game on! -2S!K Productions
