diff --git a/code/__DEFINES/atmospherics.dm b/code/__DEFINES/atmospherics.dm
index 9ed2306ecbd5..430f7f29b307 100644
--- a/code/__DEFINES/atmospherics.dm
+++ b/code/__DEFINES/atmospherics.dm
@@ -176,6 +176,4 @@
 #define ADD_GAS(gas_id, out_list)\
 	var/list/tmp_gaslist = GLOB.gaslist_cache[gas_id]; out_list[gas_id] = tmp_gaslist.Copy();
 
-//ASSERT_GAS(gas_id, gas_mixture) - used to guarantee that the gas list for this id exists in gas_mixture.gases.
-//Must be used before adding to a gas. May be used before reading from a gas.
 #define ASSERT_GAS(gas_id, gas_mixture) if (!gas_mixture.gases[gas_id]) { ADD_GAS(gas_id, gas_mixture.gases) };
diff --git a/code/game/mecha/equipment/tools/other_tools.dm b/code/game/mecha/equipment/tools/other_tools.dm
index 8951a0dbd5d2..385d11254299 100644
--- a/code/game/mecha/equipment/tools/other_tools.dm
+++ b/code/game/mecha/equipment/tools/other_tools.dm
@@ -422,7 +422,7 @@
 	if(!istype(T))
 		return
 	var/datum/gas_mixture/GM = new
-	ADD_GAS(/datum/gas/plasma, GM.gases)
+	GM.add_gas(/datum/gas/plasma)
 	if(prob(10))
 		GM.gases[/datum/gas/plasma][MOLES] += 100
 		GM.temperature = 1500+T0C //should be enough to start a fire
diff --git a/code/game/objects/effects/effect_system/effects_smoke.dm b/code/game/objects/effects/effect_system/effects_smoke.dm
index 3de8432ee9c7..4dc985c9a122 100644
--- a/code/game/objects/effects/effect_system/effects_smoke.dm
+++ b/code/game/objects/effects/effect_system/effects_smoke.dm
@@ -169,7 +169,7 @@
 				qdel(H)
 				var/list/G_gases = G.gases
 				if(G_gases[/datum/gas/plasma])
-					ASSERT_GAS(/datum/gas/nitrogen, G)
+					G.assert_gas(/datum/gas/nitrogen)
 					G_gases[/datum/gas/nitrogen][MOLES] += (G_gases[/datum/gas/plasma][MOLES])
 					G_gases[/datum/gas/plasma][MOLES] = 0
 					G.garbage_collect()
diff --git a/code/game/objects/items/tanks/jetpack.dm b/code/game/objects/items/tanks/jetpack.dm
index f1644f0b1acd..6466696b9890 100644
--- a/code/game/objects/items/tanks/jetpack.dm
+++ b/code/game/objects/items/tanks/jetpack.dm
@@ -17,7 +17,7 @@
 /obj/item/tank/jetpack/New()
 	..()
 	if(gas_type)
-		ASSERT_GAS(gas_type,air_contents)
+		air_contents.assert_gas(gas_type)
 		air_contents.gases[gas_type][MOLES] = (6 * ONE_ATMOSPHERE) * volume / (R_IDEAL_GAS_EQUATION * T20C)
 
 	ion_trail = new
diff --git a/code/game/objects/items/tanks/tank_types.dm b/code/game/objects/items/tanks/tank_types.dm
index 7a1fa569a36d..4a687b458d18 100644
--- a/code/game/objects/items/tanks/tank_types.dm
+++ b/code/game/objects/items/tanks/tank_types.dm
@@ -21,7 +21,7 @@
 
 /obj/item/tank/internals/oxygen/New()
 	..()
-	ASSERT_GAS(/datum/gas/oxygen, air_contents)
+	air_contents.assert_gas(/datum/gas/oxygen)
 	air_contents.gases[/datum/gas/oxygen][MOLES] = (6*ONE_ATMOSPHERE)*volume/(R_IDEAL_GAS_EQUATION*T20C)
 	return
 
@@ -87,7 +87,7 @@
 
 /obj/item/tank/internals/plasma/New()
 	..()
-	ASSERT_GAS(/datum/gas/plasma, air_contents)
+	air_contents.assert_gas(/datum/gas/plasma)
 	air_contents.gases[/datum/gas/plasma][MOLES] = (3*ONE_ATMOSPHERE)*volume/(R_IDEAL_GAS_EQUATION*T20C)
 	return
 
@@ -124,7 +124,7 @@
 
 /obj/item/tank/internals/plasmaman/New()
 	..()
-	ASSERT_GAS(/datum/gas/plasma, air_contents)
+	air_contents.assert_gas(/datum/gas/plasma)
 	air_contents.gases[/datum/gas/plasma][MOLES] = (3*ONE_ATMOSPHERE)*volume/(R_IDEAL_GAS_EQUATION*T20C)
 	return
 
@@ -166,7 +166,7 @@
 
 /obj/item/tank/internals/emergency_oxygen/New()
 	..()
-	ASSERT_GAS(/datum/gas/oxygen, air_contents)
+	air_contents.assert_gas(/datum/gas/oxygen)
 	air_contents.gases[/datum/gas/oxygen][MOLES] = (3*ONE_ATMOSPHERE)*volume/(R_IDEAL_GAS_EQUATION*T20C)
 	return
 
diff --git a/code/game/turfs/open.dm b/code/game/turfs/open.dm
index 5d83d677dede..0eddbc411e8d 100644
--- a/code/game/turfs/open.dm
+++ b/code/game/turfs/open.dm
@@ -355,6 +355,6 @@
 	if (air.gases[/datum/gas/carbon_dioxide] && air.gases[/datum/gas/oxygen])
 		air.gases[/datum/gas/carbon_dioxide][MOLES]=max(air.gases[/datum/gas/carbon_dioxide][MOLES]-(pulse_strength/1000),0)
 		air.gases[/datum/gas/oxygen][MOLES]=max(air.gases[/datum/gas/oxygen][MOLES]-(pulse_strength/2000),0)
-		ASSERT_GAS(/datum/gas/pluoxium,air)
+		air.assert_gas(/datum/gas/pluoxium)
 		air.gases[/datum/gas/pluoxium][MOLES]+=(pulse_strength/4000)
-		air.garbage_collect()
\ No newline at end of file
+		air.garbage_collect()
diff --git a/code/modules/admin/verbs/debug.dm b/code/modules/admin/verbs/debug.dm
index 6f16a816df44..357e69101aab 100644
--- a/code/modules/admin/verbs/debug.dm
+++ b/code/modules/admin/verbs/debug.dm
@@ -735,7 +735,7 @@ GLOBAL_PROTECT(LastAdminCalledProc)
 		if(Rad.anchored)
 			if(!Rad.loaded_tank)
 				var/obj/item/tank/internals/plasma/Plasma = new/obj/item/tank/internals/plasma(Rad)
-				ASSERT_GAS(/datum/gas/plasma, Plasma.air_contents)
+				Plasma.air_contents.assert_gas(/datum/gas/plasma)
 				Plasma.air_contents.gases[/datum/gas/plasma][MOLES] = 70
 				Rad.drainratio = 0
 				Rad.loaded_tank = Plasma
diff --git a/code/modules/atmospherics/gasmixtures/gas_mixture.dm b/code/modules/atmospherics/gasmixtures/gas_mixture.dm
index 2ebf5bd7d556..dd6e4ffe7123 100644
--- a/code/modules/atmospherics/gasmixtures/gas_mixture.dm
+++ b/code/modules/atmospherics/gasmixtures/gas_mixture.dm
@@ -37,14 +37,24 @@ GLOBAL_LIST_INIT(gaslist_cache, init_gaslist_cache())
 	reaction_results = new
 
 //listmos procs
+//use the macros in performance intensive areas. for their definitions, refer to code/__DEFINES/atmospherics.dm
 
-// The following procs used to live here: thermal_energy(), assert_gas() and add_gas(). They have been moved into defines in code/__DEFINES/atmospherics.dm
+	//assert_gas(gas_id) - used to guarantee that the gas list for this id exists in gas_mixture.gases.
+	//Must be used before adding to a gas. May be used before reading from a gas.
+/datum/gas_mixture/proc/assert_gas(gas_id)
+	ASSERT_GAS(gas_id, src)
 
 	//assert_gases(args) - shorthand for calling ASSERT_GAS() once for each gas type.
 /datum/gas_mixture/proc/assert_gases()
 	for(var/id in args)
 		ASSERT_GAS(id, src)
 
+	//add_gas(gas_id) - similar to assert_gas(), but does not check for an existing
+		//gas list for this id. This can clobber existing gases.
+	//Used instead of assert_gas() when you know the gas does not exist. Faster than assert_gas().
+/datum/gas_mixture/proc/add_gas(gas_id)
+	ADD_GAS(gas_id, gases)
+
 	//add_gases(args) - shorthand for calling add_gas() once for each gas_type.
 /datum/gas_mixture/proc/add_gases()
 	var/cached_gases = gases
@@ -101,6 +111,9 @@ GLOBAL_LIST_INIT(gaslist_cache, init_gaslist_cache())
 /datum/gas_mixture/proc/return_volume() //liters
 	return max(0, volume)
 
+/datum/gas_mixture/proc/thermal_energy() //joules
+	return THERMAL_ENERGY(src) //see code/__DEFINES/atmospherics.dm; use the define in performance critical areas
+
 /datum/gas_mixture/proc/archive()
 	//Update archived versions of variables
 	//Returns: 1 in all cases
diff --git a/code/modules/atmospherics/machinery/components/trinary_devices/filter.dm b/code/modules/atmospherics/machinery/components/trinary_devices/filter.dm
index f0840f31f60c..5281c3bad79a 100644
--- a/code/modules/atmospherics/machinery/components/trinary_devices/filter.dm
+++ b/code/modules/atmospherics/machinery/components/trinary_devices/filter.dm
@@ -103,7 +103,7 @@
 			var/datum/gas_mixture/filtered_out = new
 
 			filtered_out.temperature = removed.temperature
-			ASSERT_GAS(filter_type, filtered_out)
+			filtered_out.add_gas(filter_type)
 			filtered_out.gases[filter_type][MOLES] = removed.gases[filter_type][MOLES]
 
 			removed.gases[filter_type][MOLES] = 0
diff --git a/code/modules/atmospherics/machinery/components/unary_devices/tank.dm b/code/modules/atmospherics/machinery/components/unary_devices/tank.dm
index cf93f943909d..b12eb594426c 100644
--- a/code/modules/atmospherics/machinery/components/unary_devices/tank.dm
+++ b/code/modules/atmospherics/machinery/components/unary_devices/tank.dm
@@ -17,7 +17,7 @@
 	air_contents.volume = volume
 	air_contents.temperature = T20C
 	if(gas_type)
-		ASSERT_GAS(gas_type, air_contents)
+		air_contents.assert_gas(gas_type)
 		air_contents.gases[gas_type][MOLES] = AIR_CONTENTS
 		name = "[name] ([air_contents.gases[gas_type][GAS_META][META_GAS_NAME]])"
 
diff --git a/code/modules/atmospherics/machinery/components/unary_devices/vent_scrubber.dm b/code/modules/atmospherics/machinery/components/unary_devices/vent_scrubber.dm
index e1293ab01b56..2b9d6cc7e5c7 100644
--- a/code/modules/atmospherics/machinery/components/unary_devices/vent_scrubber.dm
+++ b/code/modules/atmospherics/machinery/components/unary_devices/vent_scrubber.dm
@@ -175,7 +175,7 @@
 			filtered_out.temperature = removed.temperature
 
 			for(var/gas in filter_types & removed_gases)
-				ADD_GAS(gas, filtered_gases)
+				filtered_out.add_gas(gas)
 				filtered_gases[gas][MOLES] = removed_gases[gas][MOLES]
 				removed_gases[gas][MOLES] = 0
 
diff --git a/code/modules/atmospherics/machinery/other/miner.dm b/code/modules/atmospherics/machinery/other/miner.dm
index cb28f178020a..f63065b431c4 100644
--- a/code/modules/atmospherics/machinery/other/miner.dm
+++ b/code/modules/atmospherics/machinery/other/miner.dm
@@ -132,7 +132,7 @@
 	if(!isopenturf(O))
 		return FALSE
 	var/datum/gas_mixture/merger = new
-	ASSERT_GAS(spawn_id, merger)
+	merger.assert_gas(spawn_id)
 	merger.gases[spawn_id][MOLES] = (spawn_mol)
 	merger.temperature = spawn_temp
 	O.assume_air(merger)
diff --git a/code/modules/atmospherics/machinery/portable/canister.dm b/code/modules/atmospherics/machinery/portable/canister.dm
index 653f76da30db..08b20f07bba9 100644
--- a/code/modules/atmospherics/machinery/portable/canister.dm
+++ b/code/modules/atmospherics/machinery/portable/canister.dm
@@ -196,7 +196,7 @@
 
 /obj/machinery/portable_atmospherics/canister/proc/create_gas()
 	if(gas_type)
-		ADD_GAS(gas_type, air_contents.gases)
+		air_contents.add_gas(gas_type)
 		if(starter_temp)
 			air_contents.temperature = starter_temp
 		air_contents.gases[gas_type][MOLES] = (maximum_pressure * filled) * air_contents.volume / (R_IDEAL_GAS_EQUATION * air_contents.temperature)
diff --git a/code/modules/atmospherics/machinery/portable/scrubber.dm b/code/modules/atmospherics/machinery/portable/scrubber.dm
index 3ba7e0a11004..4bb7b022884c 100644
--- a/code/modules/atmospherics/machinery/portable/scrubber.dm
+++ b/code/modules/atmospherics/machinery/portable/scrubber.dm
@@ -45,7 +45,7 @@
 
 	filtered.temperature = filtering.temperature
 	for(var/gas in filtering.gases & scrubbing)
-		ADD_GAS(gas, filtered.gases)
+		filtered.add_gas(gas)
 		filtered.gases[gas][MOLES] = filtering.gases[gas][MOLES] // Shuffle the "bad" gasses to the filtered mixture.
 		filtering.gases[gas][MOLES] = 0
 	filtering.garbage_collect() // Now that the gasses are set to 0, clean up the mixture.
diff --git a/code/modules/power/singularity/collector.dm b/code/modules/power/singularity/collector.dm
index 36dd615e8617..a5e9db1fdef7 100644
--- a/code/modules/power/singularity/collector.dm
+++ b/code/modules/power/singularity/collector.dm
@@ -37,7 +37,7 @@
 			eject()
 		else
 			loaded_tank.air_contents.gases[/datum/gas/plasma][MOLES] -= 0.001*drainratio
-			ASSERT_GAS(/datum/gas/tritium,loaded_tank.air_contents)
+			loaded_tank.air_contents.assert_gas(/datum/gas/tritium)
 			loaded_tank.air_contents.gases[/datum/gas/tritium][MOLES] += 0.001*drainratio
 			loaded_tank.air_contents.garbage_collect()