THIS FIXES IT (well it should :) )

code/modules/atmospherics/machinery/components/unary_devices/tank.dm

@@ -13,7 +13,7 @@
 
 	var/volume = 10000 //in liters
 	/// The typepath of the gas this tank should be filled with.
-	var/gas_type = null
+	var/gas_type = 0
 
 /obj/machinery/atmospherics/components/unary/tank/New()
 	..()

code/modules/atmospherics/machinery/portable/canister.dm

@@ -319,7 +319,7 @@
 	if(timing && valve_timer < world.time)
 		valve_open = !valve_open
 		timing = FALSE
-	if(!valve_open)
+	if(valve_open)
 		var/turf/T = get_turf(src)
 		var/datum/gas_mixture/target_air = holding ? holding.air_contents : T.return_air()