OOP pipe-crawling procs.

You can now weld scrubbers, which stops their airflow and also crawling through them.
There is now a proc for if a mob can ventcrawl through a pipe.

code/ATMOSPHERICS/atmospherics.dm

@@ -185,21 +185,24 @@ Pipelines + Other Objects -> Pipe network
 
 	var/obj/machinery/atmospherics/target_move = findConnecting(direction)
 	if(target_move)
-		if(is_type_in_list(target_move, ventcrawl_machinery))
+		if(is_type_in_list(target_move, ventcrawl_machinery) && target_move.can_crawl_through())
 			user.remove_ventcrawl()
 			user.forceMove(target_move.loc) //handles entering and so on
 			user.visible_message("You hear something squeezing through the ducts.", "You climb out the ventilation system.")
-		else
+		else if(target_move.can_crawl_through())
 			user.loc = target_move
 			user.client.eye = target_move //if we don't do this, Byond only updates the eye every tick - required for smooth movement
 			if(world.time - user.last_played_vent > VENT_SOUND_DELAY)
 				user.last_played_vent = world.time
 				playsound(src, 'sound/machines/ventcrawl.ogg', 50, 1, -3)
 	else
-		if((direction & initialize_directions) || is_type_in_list(src, ventcrawl_machinery)) //if we move in a way the pipe can connect, but doesn't - or we're in a vent
+		if((direction & initialize_directions) || is_type_in_list(src, ventcrawl_machinery) && src.can_crawl_through()) //if we move in a way the pipe can connect, but doesn't - or we're in a vent
 			user.remove_ventcrawl()
 			user.forceMove(src.loc)
 			user.visible_message("You hear something squeezing through the pipes.", "You climb out the ventilation system.")
 	user.canmove = 0
 	spawn(1)
 		user.canmove = 1
+
+/obj/machinery/atmospherics/proc/can_crawl_through()
+	return 1

code/ATMOSPHERICS/components/unary/vent_pump.dm

@@ -313,6 +313,9 @@
 	</ul>
 	"}
 
+/obj/machinery/atmospherics/unary/vent_pump/can_crawl_through()
+	return !welded
+
 /obj/machinery/atmospherics/unary/vent_pump/attackby(var/obj/item/W as obj, var/mob/user as mob)
 	if(istype(W, /obj/item/weapon/weldingtool))
 		var/obj/item/weapon/weldingtool/WT = W

code/ATMOSPHERICS/components/unary/vent_scrubber.dm

@@ -22,6 +22,7 @@
 
 	var/volume_rate = 1000 // 120
 	var/panic = 0 //is this scrubber panicked?
+	var/welded = 0
 
 	var/area_uid
 	var/radio_filter_out
@@ -41,6 +42,9 @@
 	var/hidden=""
 	if(level == 1 && istype(loc, /turf/simulated))
 		hidden="h"
+	if(welded)
+		icon_state = "[hidden]weld"
+		return
 	var/suffix=""
 	if(scrub_O2)
 		suffix="1"
@@ -108,6 +112,8 @@
 		return
 	if (!node)
 		return 0 // Let's not shut it off, for now.
+	if(welded)
+		return 0
 	//broadcast_status()
 	if(!on)
 		return 0
@@ -279,10 +285,33 @@
 		stat |= NOPOWER
 	update_icon()
 
+/obj/machinery/atmospherics/unary/vent_scrubber/can_crawl_through()
+	return !welded
+
 /obj/machinery/atmospherics/unary/vent_scrubber/attackby(var/obj/item/weapon/W as obj, var/mob/user as mob)
 	if(istype(W, /obj/item/device/multitool))
 		update_multitool_menu(user)
 		return 1
+	if(istype(W, /obj/item/weapon/weldingtool))
+		var/obj/item/weapon/weldingtool/WT = W
+		if (WT.remove_fuel(0,user))
+			user << "<span class='notice'>Now welding the scrubber.</span>"
+			if(do_after(user, 20))
+				if(!src || !WT.isOn()) return
+				playsound(get_turf(src), 'sound/items/Welder2.ogg', 50, 1)
+				if(!welded)
+					user.visible_message("[user] welds the scrubber shut.", "You weld the vent scrubber.", "You hear welding.")
+					welded = 1
+					update_icon()
+				else
+					user.visible_message("[user] unwelds the scrubber.", "You unweld the scrubber.", "You hear welding.")
+					welded = 0
+					update_icon()
+			else
+				user << "<span class='notice'>The welding tool needs to be on to start this task.</span>"
+		else
+			user << "<span class='notice'>You need more welding fuel to complete this task.</span>"
+			return 1
 	if (!istype(W, /obj/item/weapon/wrench))
 		return ..()
 	if (!(stat & NOPOWER) && on)

code/modules/mob/living/carbon/carbon.dm

@@ -260,19 +260,22 @@
 			var/obj/machinery/atmospherics/unary/vent_found
 
 			if(clicked_on && Adjacent(clicked_on))
-				var/obj/machinery/atmospherics/unary/vent_pump/v = clicked_on
-				if(!istype(v) || !v.welded)
 				vent_found = clicked_on
+				if(!istype(vent_found) || !vent_found.can_crawl_through())
+					vent_found = null
+
 
 			if(!vent_found)
 				for(var/obj/machinery/atmospherics/machine in range(1,src))
 					if(is_type_in_list(machine, ventcrawl_machinery))
 						vent_found = machine
 
-					var/obj/machinery/atmospherics/unary/vent_pump/v = machine
-					if(istype(v) && v.welded)
+					if(!vent_found.can_crawl_through())
 						vent_found = null
 
+					if(vent_found)
+						break
+
 			if(vent_found)
 				if(vent_found.network && (vent_found.network.normal_members.len || vent_found.network.line_members.len))