Added some documentation.

code/ZAS/Airflow.dm

@@ -1,3 +1,8 @@
+/*
+Contains helper procs for airflow, handled in /connection_group.
+*/
+
+
 mob/var/tmp/last_airflow_stun = 0
 mob/proc/airflow_stun()
 	if(stat == 2)

code/ZAS/Atom.dm

@@ -1,4 +1,4 @@
-//#define ZASDBG
+
 
 /atom/var/pressure_resistance = ONE_ATMOSPHERE
 
@@ -30,17 +30,19 @@ atom/proc/CanPass(atom/movable/mover, turf/target, height=1.5, air_group = 0)
 
 		return 1
 
+//Basically another way of calling CanPass(null, other, 0, 0) and CanPass(null, other, 1.5, 1).
+//Returns:
+// 0 - Not blocked
+// AIR_BLOCKED - Blocked
+// ZONE_BLOCKED - Not blocked, but zone boundaries will not cross.
+// BLOCKED - Blocked, zone boundaries will not cross even if opened.
 atom/proc/c_airblock(turf/other)
 	#ifdef ZASDBG
 	ASSERT(isturf(other))
 	#endif
 	return !CanPass(null, other, 0, 0) + 2*!CanPass(null, other, 1.5, 1)
 
-//Returns:
+
-// 0 - Not blocked
-// AIR_BLOCKED - Blocked
-// ZONE_BLOCKED - Not blocked, but zone boundaries will not cross.
-// BLOCKED - Blocked, zone boundaries will not cross even if opened.
 turf/c_airblock(turf/other)
 	#ifdef ZASDBG
 	ASSERT(isturf(other))

code/ZAS/Controller.dm

@@ -42,7 +42,7 @@ var/tick_multiplier = 2
 
 	for(var/turf/simulated/S in world)
 		simulated_turf_count++
-		S.c_update_air_properties()
+		S.update_air_properties()
 
 	world << {"<font color='red'><b>Geometry initialized in [round(0.1*(world.timeofday-start_time),0.1)] seconds.</b>
 Total Simulated Turfs: [simulated_turf_count]
@@ -85,7 +85,8 @@ Total Unsimulated Turfs: [world.maxx*world.maxy*world.maxz - simulated_turf_coun
 		var/updated = 0
 		#endif
 		for(var/turf/T in updating)
-			T.c_update_air_properties()
+			T.update_air_properties()
+			T.post_update_air_properties()
 			T.needs_air_update = 0
 			#ifdef ZASDBG
 			T.overlays -= mark
@@ -100,24 +101,23 @@ Total Unsimulated Turfs: [world.maxx*world.maxy*world.maxz - simulated_turf_coun
 			. = 0
 		#endif
 
-	//Rebuild zones.
+	//Where gas exchange happens.
 	if(.)
-		tick_progress = "rebuilding zones"
+		tick_progress = "processing edges"
-
-	//Check sanity on connection objects.
-	if(.)
-		tick_progress = "checking/creating connections"
-
-	//for(var/connection/c in connections)
-		//if(c.valid()) c.tick()
-		//else connections.Remove(c)
 
 	for(var/connection_edge/edge in edges)
 		edge.tick()
 
+	//Process fires.
+	if(.)
+		tick_progress = "processing fire"
+
+	for(var/obj/fire/fire in active_hotspots)
+		fire.process()
+
 	//Process zones.
 	if(.)
-		tick_progress = "processing zones"
+		tick_progress = "updating zones"
 
 	active_zones = zones_to_update.len
 	if(zones_to_update.len)
@@ -127,20 +127,6 @@ Total Unsimulated Turfs: [world.maxx*world.maxy*world.maxz - simulated_turf_coun
 			zone.tick()
 			zone.needs_update = 0
 
-	/*for(var/zone/zone in zones)
-		zone.tick()*/
-
-	//Ensure tiles still have zones.
-	if(.)
-		tick_progress = "reconsidering zones on turfs"
-
-	//Process fires.
-	if(.)
-		tick_progress = "processing fire"
-
-	for(var/obj/fire/fire in active_hotspots)
-		fire.process()
-
 	if(.)
 		tick_progress = "success"
 
@@ -221,7 +207,7 @@ Total Unsimulated Turfs: [world.maxx*world.maxy*world.maxz - simulated_turf_coun
 	ASSERT(isturf(T))
 	#endif
 	if(T.needs_air_update) return
-	tiles_to_update.Add(T)
+	tiles_to_update |= T
 	#ifdef ZASDBG
 	T.overlays += mark
 	#endif

code/ZAS/_docs.dm

@@ -6,13 +6,23 @@ This air system divides the station into impermeable areas called zones.
 When something happens, i.e. a door opening or a wall being taken down,
 zones equalize and eventually merge. Making an airtight area closes the connection again.
 
+Control Flow:
+Every air tick:
+	Marked turfs are updated with update_air_properties(), followed by post_update_air_properties().
+	Edges, including those generated by connections in the previous step, are processed. This is where gas is exchanged.
+	Fire is processed.
+	Marked zones have their air archived.
+
 Important Functions:
 
 air_master.mark_for_update(turf)
-	When stuff happens, call this. It works on everything.
+	When stuff happens, call this. It works on everything. You basically don't need to worry about any other
+	functions besides CanPass().
 
 */
 
+#define ZASDBG
+
 #define AIR_BLOCKED 1
 #define ZONE_BLOCKED 2
 #define BLOCKED 3