diff --git a/src/p_acs.cpp b/src/p_acs.cpp
index 3667d0505..9bff85433 100644
--- a/src/p_acs.cpp
+++ b/src/p_acs.cpp
@@ -97,13 +97,6 @@ FRandom pr_acs ("ACS");
 #define NOT_FLOOR			8
 #define NOT_CEILING			16
 
-// Flags for SectorDamage
-
-#define DAMAGE_PLAYERS				1
-#define DAMAGE_NONPLAYERS			2
-#define DAMAGE_IN_AIR				4
-#define DAMAGE_SUBCLASSES_PROTECT	8
-
 struct CallReturn
 {
 	CallReturn(int pc, ScriptFunction *func, FBehavior *module, SDWORD *locals, bool discard, FString &str)
@@ -6970,53 +6963,7 @@ int DLevelScript::RunScript ()
 				int flags = STACK(1);
 				sp -= 5;
 
-				int secnum = -1;
-
-				while ((secnum = P_FindSectorFromTag (tag, secnum)) >= 0)
-				{
-					AActor *actor, *next;
-					sector_t *sec = &sectors[secnum];
-
-					for (actor = sec->thinglist; actor != NULL; actor = next)
-					{
-						next = actor->snext;
-
-						if (!(actor->flags & MF_SHOOTABLE))
-							continue;
-
-						if (!(flags & DAMAGE_NONPLAYERS) && actor->player == NULL)
-							continue;
-
-						if (!(flags & DAMAGE_PLAYERS) && actor->player != NULL)
-							continue;
-
-						if (!(flags & DAMAGE_IN_AIR) && actor->z != sec->floorplane.ZatPoint (actor->x, actor->y) && !actor->waterlevel)
-							continue;
-
-						if (protectClass != NULL)
-						{
-							if (!(flags & DAMAGE_SUBCLASSES_PROTECT))
-							{
-								if (actor->FindInventory (protectClass))
-									continue;
-							}
-							else
-							{
-								AInventory *item;
-
-								for (item = actor->Inventory; item != NULL; item = item->Inventory)
-								{
-									if (item->IsKindOf (protectClass))
-										break;
-								}
-								if (item != NULL)
-									continue;
-							}
-						}
-
-						P_DamageMobj (actor, NULL, NULL, amount, type);
-					}
-				}
+				P_SectorDamage(tag, amount, type, protectClass, flags);
 			}
 			break;
 
diff --git a/src/p_spec.cpp b/src/p_spec.cpp
index a41fa2cad..e3a27201f 100644
--- a/src/p_spec.cpp
+++ b/src/p_spec.cpp
@@ -585,6 +585,77 @@ void P_PlayerInSpecialSector (player_t *player, sector_t * sector)
 	}
 }
 
+//============================================================================
+//
+// P_SectorDamage
+//
+//============================================================================
+
+static void DoSectorDamage(AActor *actor, sector_t *sec, int amount, FName type, const PClass *protectClass, int flags)
+{
+	if (!(actor->flags & MF_SHOOTABLE))
+		return;
+
+	if (!(flags & DAMAGE_NONPLAYERS) && actor->player == NULL)
+		return;
+
+	if (!(flags & DAMAGE_PLAYERS) && actor->player != NULL)
+		return;
+
+	if (!(flags & DAMAGE_IN_AIR) && actor->z != sec->floorplane.ZatPoint(actor->x, actor->y) && !actor->waterlevel)
+		return;
+
+	if (protectClass != NULL)
+	{
+		if (actor->FindInventory(protectClass, !!(flags & DAMAGE_SUBCLASSES_PROTECT)))
+			return;
+	}
+
+	P_DamageMobj (actor, NULL, NULL, amount, type);
+}
+
+void P_SectorDamage(int tag, int amount, FName type, const PClass *protectClass, int flags)
+{
+	int secnum = -1;
+
+	while ((secnum = P_FindSectorFromTag (tag, secnum)) >= 0)
+	{
+		AActor *actor, *next;
+		sector_t *sec = &sectors[secnum];
+
+		// Do for actors in this sector.
+		for (actor = sec->thinglist; actor != NULL; actor = next)
+		{
+			next = actor->snext;
+			DoSectorDamage(actor, sec, amount, type, protectClass, flags);
+		}
+		// If this is a 3D floor control sector, also do for anything in/on
+		// those 3D floors.
+		for (unsigned i = 0; i < sec->e->XFloor.attached.Size(); ++i)
+		{
+			sector_t *sec2 = sec->e->XFloor.attached[i];
+
+			for (actor = sec2->thinglist; actor != NULL; actor = next)
+			{
+				next = actor->snext;
+				// Only affect actors touching the 3D floor
+				if (actor->z + actor->height > sec->floorplane.ZatPoint(actor->x, actor->y))
+				{
+					// If DAMAGE_IN_AIR is used, anything not beneath the 3D floor will be
+					// damaged (so, anything touching it or above it). Other 3D floors between
+					// the actor and this one will not stop this effect.
+					if ((flags & DAMAGE_IN_AIR) || actor->z <= sec->ceilingplane.ZatPoint(actor->x, actor->y))
+					{
+						// Here we pass the DAMAGE_IN_AIR flag to disable the floor check, since it
+						// only works with the real sector's floor. We did the appropriate height checks
+						// for 3D floors already.
+						DoSectorDamage(actor, NULL, amount, type, protectClass, flags | DAMAGE_IN_AIR);
+					}
+				}
+			}
+		}
+	}
+}
 
 //============================================================================
 //
diff --git a/src/p_spec.h b/src/p_spec.h
index d30fb4f83..81051eb8e 100644
--- a/src/p_spec.h
+++ b/src/p_spec.h
@@ -145,6 +145,12 @@ bool PIT_PushThing (AActor *thing);
 // Define values for map objects
 #define MO_TELEPORTMAN			14
 
+// Flags for P_SectorDamage
+#define DAMAGE_PLAYERS				1
+#define DAMAGE_NONPLAYERS			2
+#define DAMAGE_IN_AIR				4
+#define DAMAGE_SUBCLASSES_PROTECT	8
+
 
 // [RH] If a deathmatch game, checks to see if noexit is enabled.
 //		If so, it kills the player and returns false. Otherwise,
@@ -163,7 +169,7 @@ bool	P_TestActivateLine (line_t *ld, AActor *mo, int side, int activationType);
 
 void 	P_PlayerInSpecialSector (player_t *player, sector_t * sector=NULL);
 void	P_PlayerOnSpecialFlat (player_t *player, int floorType);
-
+void	P_SectorDamage(int tag, int amount, FName type, const PClass *protectClass, int flags);
 void	P_SetSectorFriction (int tag, int amount, bool alterFlag);
 
 void P_GiveSecret(AActor *actor, bool printmessage, bool playsound);