Gas visuals use vis_contents not overlays

code/modules/admin/verbs/grief_fixers.dm

@@ -40,7 +40,7 @@
 
 	for(var/turf/simulated/T in world)
 		T.air = null
-		T.overlays.Remove(unsorted_overlays)
+		T.vis_contents.Remove(unsorted_overlays)
 		T.zone = null
 
 	to_chat(usr, "\[4/5\] - All turfs reset to roundstart values.")

code/modules/xgm/xgm_gas_data.dm

@@ -39,8 +39,18 @@
 		gas_data.name[gas.id] = gas.name
 		gas_data.specific_heat[gas.id] = gas.specific_heat
 		gas_data.molar_mass[gas.id] = gas.molar_mass
-		if(gas.tile_overlay) gas_data.tile_overlay[gas.id] = image('icons/effects/tile_effects.dmi', gas.tile_overlay, FLY_LAYER)
-		if(gas.overlay_limit) gas_data.overlay_limit[gas.id] = gas.overlay_limit
+		if(gas.tile_overlay)
+			gas_data.tile_overlay[gas.id] = new /atom/movable/gas_visuals(null, gas.tile_overlay)
+		if(gas.overlay_limit)	
+			gas_data.overlay_limit[gas.id] = gas.overlay_limit
 		gas_data.flags[gas.id] = gas.flags
 
 	return 1
+
+/atom/movable/gas_visuals
+	icon = 'icons/effects/tile_effects.dmi'
+	mouse_opacity = 0
+	plane = ABOVE_MOB_PLANE
+/atom/movable/gas_visuals/New(newloc, ico)
+	..()
+	icon_state = ico