diff --git a/code/modules/mob/living/simple_animal/friendly/mouse.dm b/code/modules/mob/living/simple_animal/friendly/mouse.dm
index 9fd3794520..66b4bd5e73 100644
--- a/code/modules/mob/living/simple_animal/friendly/mouse.dm
+++ b/code/modules/mob/living/simple_animal/friendly/mouse.dm
@@ -99,15 +99,17 @@
 		evolve()
 		return
 	for(var/obj/item/trash/garbage in range(1, src))
-		if(prob(2))
-			qdel(garbage)
-			evolve_plague()
-			return
+		if(is_station_level(z))
+			if(prob(2))
+				qdel(garbage)
+				evolve_plague()
+				return
 	for(var/obj/effect/decal/cleanable/blood/gibs/leftovers in range(1, src))
-		if(prob(2))
-			qdel(leftovers)
-			evolve_plague()
-			return
+		if(is_station_level(z))
+			if(prob(2))
+				qdel(leftovers)
+				evolve_plague()
+				return
 
 /**
   *Checks the mouse cap, if it's above the cap, doesn't spawn a mouse. If below, spawns a mouse and adds it to cheeserats.
@@ -202,4 +204,5 @@ GLOBAL_VAR(tom_existed)
 
 /mob/living/simple_animal/mouse/handle_environment(datum/gas_mixture/environment)
 	. = ..()
-	miasma()
+	if(is_station_level(z))
+		miasma()
diff --git a/code/modules/mob/living/simple_animal/hostile/plaguerat.dm b/code/modules/mob/living/simple_animal/hostile/plaguerat.dm
index 331dc1eb75..2b92894317 100644
--- a/code/modules/mob/living/simple_animal/hostile/plaguerat.dm
+++ b/code/modules/mob/living/simple_animal/hostile/plaguerat.dm
@@ -1,3 +1,6 @@
+#define RAT_VENT_CHANCE 1.75
+GLOBAL_LIST_EMPTY(plague_rats)
+
 /mob/living/simple_animal/hostile/plaguerat
 	name = "plague rat"
 	desc = "A large decaying rat.  It spreads its filth and emits a putrid odor to create more of its kind."
@@ -11,8 +14,8 @@
 	gender = NEUTER
 	speak_chance = 1
 	turns_per_move = 5
-	maxHealth = 15
-	health = 15
+	maxHealth = 100
+	health = 100
 	see_in_dark = 6
 	obj_damage = 10
 	butcher_results = list(/obj/item/reagent_containers/food/snacks/meat/slab = 1)
@@ -22,8 +25,8 @@
 	response_disarm_simple = "skoff at"
 	response_harm_continuous = "slashes"
 	response_harm_simple = "slash"
-	melee_damage_lower = 5
-	melee_damage_upper = 7
+	melee_damage_lower = 6
+	melee_damage_upper = 8
 	attack_verb_continuous = "slashes"
 	attack_verb_simple = "slash"
 	attack_sound = 'sound/weapons/punch1.ogg'
@@ -34,27 +37,69 @@
 	mob_biotypes = MOB_ORGANIC|MOB_BEAST
 	var/datum/action/cooldown/scavenge
 	var/last_spawn_time = 0
-	///Number assigned to rats and mice, checked when determining infighting.
+	var/in_vent = FALSE
+	var/min_next_vent = 0
+	var/obj/machinery/atmospherics/components/unary/entry_vent
+	var/obj/machinery/atmospherics/components/unary/exit_vent
 
 /mob/living/simple_animal/hostile/plaguerat/Initialize()
 	. = ..()
-	SSmobs.cheeserats += src
+	GLOB.plague_rats += src
 	AddComponent(/datum/component/swarming)
 	AddElement(/datum/element/ventcrawling, given_tier = VENTCRAWLER_ALWAYS)
 	scavenge = new /datum/action/cooldown/scavenge
 	scavenge.Grant(src)
 
 /mob/living/simple_animal/hostile/plaguerat/Destroy()
-	SSmobs.cheeserats -= src
+	GLOB.plague_rats -= src
 	return ..()
 
+/mob/living/simple_animal/hostile/plaguerat/Life(seconds, times_fired)
+	. = ..()
+	//Don't try to path to one target for too long. If it takes longer than a certain amount of time, assume it can't be reached and find a new one
+	//Literally only here to prevent farming and that's it.
+	if(!client) //don't do this shit if there's a client, they're capable of ventcrawling manually
+		if(in_vent)
+			target = null
+		if(entry_vent && get_dist(src, entry_vent) <= 1)
+			var/list/vents = list()
+			var/datum/pipeline/entry_vent_parent = entry_vent.parents[1]
+			for(var/obj/machinery/atmospherics/components/unary/temp_vent in entry_vent_parent.other_atmosmch)
+				vents += temp_vent
+			if(!vents.len)
+				entry_vent = null
+				in_vent = FALSE
+				return
+			exit_vent = pick(vents)
+			visible_message("<span class='notice'>[src] crawls into the ventilation ducts!</span>")
+
+			loc = exit_vent
+			var/travel_time = round(get_dist(loc, exit_vent.loc) / 2)
+			addtimer(CALLBACK(src, .proc/exit_vents), travel_time) //come out at exit vent in 2 to 20 seconds
+
+
+		if(world.time > min_next_vent && !entry_vent && !in_vent && prob(RAT_VENT_CHANCE)) //small chance to go into a vent
+			for(var/obj/machinery/atmospherics/components/unary/v in view(7,src))
+				if(!v.welded)
+					entry_vent = v
+					in_vent = TRUE
+					walk_to(src, entry_vent)
+					break
+
 /mob/living/simple_animal/hostile/plaguerat/BiologicalLife(seconds, times_fired)
 	if(!(. = ..()))
 		return
 	if(isopenturf(loc))
 		var/turf/open/T = src.loc
+		var/datum/gas_mixture/stank = new
+		var/miasma_moles = T.air.get_moles(GAS_MIASMA)
+		stank.set_moles(GAS_MIASMA,5)
+		stank.set_temperature(BODYTEMP_NORMAL)
 		if(T.air)
-			T.atmos_spawn_air("miasma=5;TEMP=293.15")
+			if(miasma_moles < 200)
+				T.assume_air(stank)
+				T.air_update_turf()
+
 	if(prob(40))
 		scavenge.Trigger()
 	if(prob(50))
@@ -66,9 +111,10 @@
 				playsound(src, 'sound/effects/sparks2.ogg', 100, TRUE)
 				C.deconstruct()
 	for(var/obj/O in range(1,src))
-		if(istype(O, /obj/item/trash) || istype(O, /obj/effect/decal/cleanable/blood/gibs))
+		if((world.time - last_spawn_time) > 10 SECONDS && istype(O, /obj/item/trash) || istype(O, /obj/effect/decal/cleanable/blood/gibs))
 			qdel(O)
 			be_fruitful()
+			last_spawn_time = world.time
 
 /mob/living/simple_animal/hostile/plaguerat/CanAttack(atom/the_target)
 	if(istype(the_target,/mob/living/simple_animal))
@@ -86,14 +132,29 @@
   */
 
 /mob/living/simple_animal/hostile/plaguerat/proc/be_fruitful()
-	var/cap = CONFIG_GET(number/ratcap)
-	if(LAZYLEN(SSmobs.cheeserats) >= cap)
+	var/cap = 10
+	if(LAZYLEN(GLOB.plague_rats) >= cap)
 		visible_message("<span class='warning'>[src] gnaws into its food, [cap] rats are now on the station!</span>")
 		return
 	var/mob/living/newmouse = new /mob/living/simple_animal/hostile/plaguerat(loc)
-	SSmobs.cheeserats += newmouse
 	visible_message("<span class='notice'>[src] gnaws into its food, attracting another rat!</span>")
 
+/mob/living/simple_animal/hostile/plaguerat/proc/exit_vents()
+	if(!exit_vent || exit_vent.welded)
+		loc = entry_vent
+		entry_vent = null
+		return
+	loc = exit_vent.loc
+	entry_vent = null
+	exit_vent = null
+	in_vent = FALSE
+	var/area/new_area = get_area(loc)
+	message_admins("[src] came out at [new_area][ADMIN_JMP(loc)]!")
+	if(new_area)
+		new_area.Entered(src)
+	visible_message("<span class='notice'>[src] climbs out of the ventilation ducts!</span>")
+	min_next_vent = world.time + 900 //90 seconds between ventcrawls
+
 /**
   *Creates a chance to spawn more trash or gibs to repopulate.  Otherwise, spawns a corpse or dirt.
   */
@@ -116,16 +177,12 @@
 		if(1 to 3)
 			var/pickedtrash = pick(GLOB.ratking_trash)
 			to_chat(owner, "<span class='notice'>Excellent, you find more trash to spread your filth!</span>")
-			new /obj/effect/decal/cleanable/dirt(T)
 			new pickedtrash(T)
 		if(4 to 6)
 			to_chat(owner, "<span class='notice'>You find blood and gibs to feed your young!</span>")
 			new /obj/effect/decal/cleanable/blood/gibs(T)
-			new /obj/effect/decal/cleanable/blood/(T)
-		if(7 to 18)
-			to_chat(owner, "<span class='notice'>A corpse rises from the ground. Best to leave it alone.</span>")
-			new /obj/effect/mob_spawn/human/corpse/assistant(T)
-		if(19 to 100)
+			if(!locate(/obj/effect/decal/cleanable/blood) in T)
+				new /obj/effect/decal/cleanable/blood/(T)
+		if(7 to 100)
 			to_chat(owner, "<span class='notice'>Drat. Nothing.</span>")
-			new /obj/effect/decal/cleanable/dirt(T)
 	StartCooldown()