diff --git a/code/__HELPERS/unsorted.dm b/code/__HELPERS/unsorted.dm
index f9c2c90dd57..c5ec1748419 100644
--- a/code/__HELPERS/unsorted.dm
+++ b/code/__HELPERS/unsorted.dm
@@ -1267,6 +1267,7 @@ proc/is_hot(obj/item/W as obj)
 
 //Is this even used for anything besides balloons? Yes I took out the W:lit stuff because : really shouldnt be used.
 /proc/is_sharp(obj/item/W as obj)		// For the record, WHAT THE HELL IS THIS METHOD OF DOING IT?
+	if(!W) return 0
 	if(W.sharp) return 1
 	return ( \
 		W.sharp													  || \
@@ -1374,4 +1375,4 @@ var/list/WALLITEMS = list(
 	return 0
 
 /proc/format_text(text)
-	return replacetext(replacetext(text,"\proper ",""),"\improper ","")
\ No newline at end of file
+	return replacetext(replacetext(text,"\proper ",""),"\improper ","")
diff --git a/code/game/machinery/alarm.dm b/code/game/machinery/alarm.dm
index f2a069c4543..c781bb20c99 100644
--- a/code/game/machinery/alarm.dm
+++ b/code/game/machinery/alarm.dm
@@ -183,24 +183,25 @@
 
 		var/datum/gas_mixture/gas
 		gas = location.remove_air(0.25*environment.total_moles)
-		var/heat_capacity = gas.heat_capacity()
-		var/energy_used = min( abs( heat_capacity*(gas.temperature - target_temperature) ), MAX_ENERGY_CHANGE)
+		if(gas)
+			var/heat_capacity = gas.heat_capacity()
+			var/energy_used = min( abs( heat_capacity*(gas.temperature - target_temperature) ), MAX_ENERGY_CHANGE)
 
-		//Use power.  Assuming that each power unit represents 1000 watts....
-		use_power(energy_used/1000, ENVIRON)
+			//Use power.  Assuming that each power unit represents 1000 watts....
+			use_power(energy_used/1000, ENVIRON)
 
-		//We need to cool ourselves.
-		if(environment.temperature > target_temperature)
-			gas.temperature -= energy_used/heat_capacity
-		else
-			gas.temperature += energy_used/heat_capacity
+			//We need to cool ourselves.
+			if(environment.temperature > target_temperature)
+				gas.temperature -= energy_used/heat_capacity
+			else
+				gas.temperature += energy_used/heat_capacity
 
-		environment.merge(gas)
+			environment.merge(gas)
 
-		if(abs(environment.temperature - target_temperature) <= 0.5)
-			regulating_temperature = 0
-			visible_message("\The [src] clicks quietly as it stops [environment.temperature > target_temperature ? "cooling" : "heating"] the room.",\
-			"You hear a click as a faint electronic humming stops.")
+			if(abs(environment.temperature - target_temperature) <= 0.5)
+				regulating_temperature = 0
+				visible_message("\The [src] clicks quietly as it stops [environment.temperature > target_temperature ? "cooling" : "heating"] the room.",\
+				"You hear a click as a faint electronic humming stops.")
 
 	var/old_level = danger_level
 	danger_level = overall_danger_level()
@@ -1683,4 +1684,4 @@ Code shamelessly copied from apc_frame
 	else
 		usr << browse(null, "window=partyalarm")
 		return
-	return
\ No newline at end of file
+	return
diff --git a/code/game/objects/items/devices/PDA/PDA.dm b/code/game/objects/items/devices/PDA/PDA.dm
index 5a0bdf4af30..df04ddfcfe7 100755
--- a/code/game/objects/items/devices/PDA/PDA.dm
+++ b/code/game/objects/items/devices/PDA/PDA.dm
@@ -482,7 +482,8 @@ var/global/list/obj/item/device/pda/PDAs = list()
 		return 0
 	if(!can_use()) //Why reinvent the wheel? There's a proc that does exactly that.
 		U.unset_machine()
-		ui.close()
+		if(ui)
+			ui.close()
 		return 0
 
 	add_fingerprint(U)
diff --git a/code/game/objects/items/weapons/swords_axes_etc.dm b/code/game/objects/items/weapons/swords_axes_etc.dm
index 8b9d914bc24..7ee3499c1cd 100644
--- a/code/game/objects/items/weapons/swords_axes_etc.dm
+++ b/code/game/objects/items/weapons/swords_axes_etc.dm
@@ -153,7 +153,7 @@
 	playsound(src.loc, 'sound/weapons/empty.ogg', 50, 1)
 	add_fingerprint(user)
 
-	if(blood_overlay && (blood_DNA.len >= 1)) //updates blood overlay, if any
+	if(blood_overlay && blood_DNA && (blood_DNA.len >= 1)) //updates blood overlay, if any
 		overlays.Cut()//this might delete other item overlays as well but eeeeeeeh
 
 		var/icon/I = new /icon(src.icon, src.icon_state)
@@ -265,4 +265,4 @@
 		H.update_inv_r_hand()
 
 	add_fingerprint(user)
-	return
\ No newline at end of file
+	return
diff --git a/code/modules/mob/living/carbon/human/life.dm b/code/modules/mob/living/carbon/human/life.dm
index 00368c2debd..8470095cde0 100644
--- a/code/modules/mob/living/carbon/human/life.dm
+++ b/code/modules/mob/living/carbon/human/life.dm
@@ -325,7 +325,7 @@
 
 					breath = loc.remove_air(breath_moles)
 
-					if(istype(wear_mask, /obj/item/clothing/mask/gas))
+					if(istype(wear_mask, /obj/item/clothing/mask/gas) && breath)
 						var/obj/item/clothing/mask/gas/G = wear_mask
 						var/datum/gas_mixture/filtered = new
 
diff --git a/code/modules/projectiles/targeting.dm b/code/modules/projectiles/targeting.dm
index 06f25a7e18b..d627a5c7713 100644
--- a/code/modules/projectiles/targeting.dm
+++ b/code/modules/projectiles/targeting.dm
@@ -269,7 +269,7 @@ client/proc/add_gun_icons()
 		screen += usr.gun_run_icon
 
 client/proc/remove_gun_icons()
-	if(isnull(usr)) return 1 // Runtime prevention on N00k agents spawning with SMG
+	if(!usr) return 1 // Runtime prevention on N00k agents spawning with SMG
 	screen -= usr.item_use_icon
 	screen -= usr.gun_move_icon
 	if (target_can_move)
diff --git a/code/modules/reagents/Chemistry-Reagents.dm b/code/modules/reagents/Chemistry-Reagents.dm
index b48b96d3095..0897d64ef84 100644
--- a/code/modules/reagents/Chemistry-Reagents.dm
+++ b/code/modules/reagents/Chemistry-Reagents.dm
@@ -935,8 +935,9 @@ datum
 					for(var/mob/living/carbon/slime/M in T)
 						M.adjustToxLoss(rand(5,10))
 			reaction_turf(var/turf/simulated/S, var/volume)
-				if(volume >= 1)
-					S.dirt = 0
+				if(istype(S))
+					if(volume >= 1)
+						S.dirt = 0
 
 			reaction_mob(var/mob/M, var/method=TOUCH, var/volume)
 				if(iscarbon(M))
@@ -3699,4 +3700,4 @@ datum
 				return
 
 // Undefine the alias for REAGENTS_EFFECT_MULTIPLER
-#undef REM
\ No newline at end of file
+#undef REM