diff --git a/common.lua b/common.lua
index d95e4c6..a3437f7 100644
--- a/common.lua
+++ b/common.lua
@@ -2,11 +2,17 @@
 
 vacuum.air_bottle_image = "vessels_steel_bottle.png^[colorize:#0000FFAA"
 
--- returns true, if in space (with safety margin for abm)
+-- space pos checker
 vacuum.is_pos_in_space = function(pos)
-	return pos.y > vacuum.space_height + 40
+	return pos.y > vacuum.space_height
 end
 
-vacuum.is_pos_on_earth = function(pos)
-	return pos.y < vacuum.space_height - 40
-end
\ No newline at end of file
+-- (cheaper) space check, gets called more often than `is_pos_in_space`
+vacuum.no_vacuum_abm = function(pos)
+	return pos.y > vacuum.space_height - 40 and pos.y < vacuum.space_height + 40
+end
+
+-- checks if this mapblock is in space when generated
+vacuum.is_mapgen_block_in_space = function(minp, maxp)
+	return minp.y > vacuum.space_height
+end
diff --git a/mapgen.lua b/mapgen.lua
index 0a5b83a..23cd27f 100644
--- a/mapgen.lua
+++ b/mapgen.lua
@@ -5,7 +5,7 @@ local c_air = minetest.get_content_id("air")
 
 minetest.register_on_generated(function(minp, maxp, seed)
 
-	if minp.y < vacuum.space_height then
+	if not vacuum.is_mapgen_block_in_space(minp, maxp) then
 		return
 	end
 
diff --git a/physics.lua b/physics.lua
index dddd967..f0c6cea 100644
--- a/physics.lua
+++ b/physics.lua
@@ -50,7 +50,7 @@ end
 
 -- vacuum/air propagation
 minetest.register_abm({
-        label = "space vacuum",
+  label = "space vacuum",
 	nodenames = {"air"},
 	neighbors = {"vacuum:vacuum"},
 	interval = 1,
@@ -59,14 +59,18 @@ minetest.register_abm({
 
 		if metric_space_vacuum_abm ~= nil then metric_space_vacuum_abm.inc() end
 
-		if vacuum.is_pos_on_earth(pos) or near_powered_airpump(pos) then
+    if vacuum.no_vacuum_abm(pos) then
+      return
+    end
+
+		if not vacuum.is_pos_in_space(pos) or near_powered_airpump(pos) then
 			-- on earth or near a powered airpump
 			local node = minetest.find_node_near(pos, 1, {"vacuum:vacuum"})
 
 			if node ~= nil then
 				minetest.set_node(node, {name = "air"})
 			end
-		elseif vacuum.is_pos_in_space(pos) then
+		else
 			-- in space, evacuate air
 			minetest.set_node(pos, {name = "vacuum:vacuum"})
 		end
@@ -183,10 +187,10 @@ minetest.register_abm({
 	action = throttle(250, function(pos)
     if metric_space_vacuum_leak_abm ~= nil then metric_space_vacuum_leak_abm.inc() end
 
-		if vacuum.is_pos_on_earth(pos) or near_powered_airpump(pos) then
+		if not vacuum.is_pos_in_space(pos) or near_powered_airpump(pos) then
 			-- on earth: TODO: replace vacuum with air
 			return
-		elseif vacuum.is_pos_in_space(pos) then
+		else
 			local node = minetest.get_node(pos)
 
 			if node.name == "pipeworks:entry_panel_empty" or node.name == "pipeworks:entry_panel_loaded" then
diff --git a/vacuum.lua b/vacuum.lua
index 1e1388b..9afea4c 100644
--- a/vacuum.lua
+++ b/vacuum.lua
@@ -13,6 +13,7 @@ minetest.register_node("vacuum:vacuum", {
 	alpha = 0.1,
 	groups = {not_in_creative_inventory=1, not_blocking_trains=1, cools_lava=1},
 	paramtype = "light",
+	-- light_source = minetest.LIGHT_MAX, TOOD: test
 	drop = {},
 	sunlight_propagates = true
 })