ERT idiotproofing and minor tweaks (#13834)

* makes ert more robust

* renamed and tweaked

* idiot proofing of ert

* I cannot into git, oops

* removed the anti-stun from code red erts again

* removed implied src

code/game/objects/items/weapons/storage/boxes.dm

@@ -1053,7 +1053,7 @@
 /obj/item/storage/box/responseteam/New()
 	..()
 	new /obj/item/clothing/mask/breath(src)
-	new /obj/item/tank/emergency_oxygen/engi(src)
+	new /obj/item/tank/emergency_oxygen/engi/full(src)
 	new /obj/item/flashlight/flare(src)
 	new /obj/item/kitchen/knife/combat(src)
 	new /obj/item/radio/centcom(src)

code/game/objects/items/weapons/tanks/tank_types.dm

@@ -167,6 +167,11 @@
 	icon_state = "emergency_engi"
 	volume = 6
 
+/obj/item/tank/emergency_oxygen/engi/full/New()
+	..()
+	air_contents.oxygen = (10*ONE_ATMOSPHERE)*volume/(R_IDEAL_GAS_EQUATION*T20C)
+
+
 /obj/item/tank/emergency_oxygen/engi/empty/New()
 	..()
 	air_contents.oxygen = null