diff --git a/code/ZAS/ConnectionGroup.dm b/code/ZAS/ConnectionGroup.dm
index f377efe74fa..94df46ac015 100644
--- a/code/ZAS/ConnectionGroup.dm
+++ b/code/ZAS/ConnectionGroup.dm
@@ -180,7 +180,8 @@ Class Procs:
 	air_master.mark_zone_update(B)
 
 /connection_edge/zone/recheck()
-	if(!A.air.compare(B.air))
+	// Edges with only one side being vacuum need processing no matter how close.
+	if(!A.air.compare(B.air, vacuum_exception = 1))
 		air_master.mark_edge_active(src)
 
 //Helper proc to get connections for a zone.
@@ -235,7 +236,10 @@ Class Procs:
 	air_master.mark_zone_update(A)
 
 /connection_edge/unsimulated/recheck()
-	if(!A.air.compare(air))
+	// Edges with only one side being vacuum need processing no matter how close.
+	// Note: This handles the glaring flaw of a room holding pressure while exposed to space, but
+	// does not specially handle the less common case of a simulated room exposed to an unsimulated pressurized turf.
+	if(!A.air.compare(air, vacuum_exception = 1))
 		air_master.mark_edge_active(src)
 
 proc/ShareHeat(datum/gas_mixture/A, datum/gas_mixture/B, connecting_tiles)
diff --git a/code/modules/xgm/xgm_gas_mixture.dm b/code/modules/xgm/xgm_gas_mixture.dm
index 6f17fba409e..cb600f254f7 100644
--- a/code/modules/xgm/xgm_gas_mixture.dm
+++ b/code/modules/xgm/xgm_gas_mixture.dm
@@ -96,10 +96,16 @@
 	update_values()
 
 
+// Used to equalize the mixture between two zones before sleeping an edge.
 /datum/gas_mixture/proc/equalize(datum/gas_mixture/sharer)
 	var/our_heatcap = heat_capacity()
 	var/share_heatcap = sharer.heat_capacity()
 
+	// Special exception: there isn't enough air around to be worth processing this edge next tick, zap both to zero.
+	if(total_moles + sharer.total_moles <= MINIMUM_AIR_TO_SUSPEND)
+		gas.Cut()
+		sharer.gas.Cut()
+
 	for(var/g in gas|sharer.gas)
 		var/comb = gas[g] + sharer.gas[g]
 		comb /= volume + sharer.volume
@@ -282,9 +288,16 @@
 
 
 //Checks if we are within acceptable range of another gas_mixture to suspend processing or merge.
-/datum/gas_mixture/proc/compare(const/datum/gas_mixture/sample)
+/datum/gas_mixture/proc/compare(const/datum/gas_mixture/sample, var/vacuum_exception = 0)
 	if(!sample) return 0
 
+	if(vacuum_exception)
+		// Special case - If one of the two is zero pressure, the other must also be zero.
+		// This prevents suspending processing when an air-filled room is next to a vacuum,
+		// an edge case which is particually obviously wrong to players
+		if(total_moles == 0 && sample.total_moles != 0 || sample.total_moles == 0 && total_moles != 0)
+			return 0
+
 	var/list/marked = list()
 	for(var/g in gas)
 		if((abs(gas[g] - sample.gas[g]) > MINIMUM_AIR_TO_SUSPEND) && \