diff --git a/code/_onclick/hud/screen_objects.dm b/code/_onclick/hud/screen_objects.dm
index 47f19fd7123..ed054ae6c8a 100644
--- a/code/_onclick/hud/screen_objects.dm
+++ b/code/_onclick/hud/screen_objects.dm
@@ -295,8 +295,13 @@
 							for(var/i=1, i<tankcheck.len+1, ++i)
 								if(istype(tankcheck[i], /obj/item/weapon/tank))
 									var/obj/item/weapon/tank/t = tankcheck[i]
-									switch(breathes)
-										if("nitrogen") 
+									if (!isnull(t.manipulated_by) && t.manipulated_by != C.real_name && findtext(t.desc,breathes))
+										contents.Add(t.air_contents.total_moles)	//Someone messed with the tank and put unknown gasses
+										continue					//in it, so we're going to believe the tank is what it says it is
+									switch(breathes)					
+																		//These tanks we're sure of their contents
+										if("nitrogen") 							//So we're a bit more picky about them.
+											
 											if(t.air_contents.nitrogen && !t.air_contents.oxygen)
 												contents.Add(t.air_contents.nitrogen)
 											else
diff --git a/code/game/machinery/atmoalter/canister.dm b/code/game/machinery/atmoalter/canister.dm
index 1d5f210dd33..d8b85211501 100644
--- a/code/game/machinery/atmoalter/canister.dm
+++ b/code/game/machinery/atmoalter/canister.dm
@@ -255,6 +255,8 @@ Release Pressure: <A href='?src=\ref[src];pressure_adj=-1000'>-</A> <A href='?sr
 
 		if (href_list["remove_tank"])
 			if(holding)
+				if(istype(holding, /obj/item/weapon/tank))
+					holding.manipulated_by = usr.real_name
 				holding.loc = loc
 				holding = null
 
diff --git a/code/game/objects/items/devices/PDA/PDA.dm b/code/game/objects/items/devices/PDA/PDA.dm
index 9123617f2a7..2750af1b05b 100755
--- a/code/game/objects/items/devices/PDA/PDA.dm
+++ b/code/game/objects/items/devices/PDA/PDA.dm
@@ -1042,6 +1042,9 @@ var/global/list/obj/item/device/pda/PDAs = list()
 
 		if(5)
 			if((istype(A, /obj/item/weapon/tank)) || (istype(A, /obj/machinery/portable_atmospherics)))
+				if(istype(A, /obj/item/weapon/tank))
+					var/obj/item/weapon/tank/t = A
+					t.manipulated_by = user.real_name
 				var/obj/icon = A
 				for (var/mob/O in viewers(user, null))
 					O << "\red [user] has used [src] on \icon[icon] [A]"
diff --git a/code/game/objects/items/weapons/tanks/tanks.dm b/code/game/objects/items/weapons/tanks/tanks.dm
index 143ff13a041..e0e30e60cb9 100644
--- a/code/game/objects/items/weapons/tanks/tanks.dm
+++ b/code/game/objects/items/weapons/tanks/tanks.dm
@@ -15,7 +15,8 @@
 	var/distribute_pressure = ONE_ATMOSPHERE
 	var/integrity = 3
 	var/volume = 70
-
+	var/manipulated_by = null		//Used by _onclick/hud/screen_objects.dm internals to determine if someone has messed with our tank or not.
+						//If they have and we haven't scanned it with the PDA or gas analyzer then we might just breath whatever they put in it.
 /obj/item/weapon/tank/New()
 	..()
 
@@ -86,7 +87,7 @@
 			O << "\red [user] has used [W] on \icon[icon] [src]"
 
 		var/pressure = air_contents.return_pressure()
-
+		manipulated_by = user.real_name			//This person is aware of the contents of the tank.
 		var/total_moles = air_contents.total_moles()
 
 		user << "\blue Results of analysis of \icon[icon]"
@@ -261,4 +262,4 @@
 			integrity--
 
 	else if(integrity < 3)
-		integrity++
\ No newline at end of file
+		integrity++