diff --git a/src/ChunkManager.cpp b/src/ChunkManager.cpp
index ce03ecc..876a120 100644
--- a/src/ChunkManager.cpp
+++ b/src/ChunkManager.cpp
@@ -85,7 +85,8 @@ void ChunkManager::destroyChunk(std::tuple<int, int, uint64_t> chunkPos) {
     Chunk* chunk = chunks[chunkPos];
 
     // unspawn all of the mobs/npcs
-    for (uint32_t id : chunk->NPCs) {
+    std::set npcIDs(chunk->NPCs);
+    for (uint32_t id : npcIDs) {
         NPCManager::destroyNPC(id);
     }
 
diff --git a/src/ChunkManager.hpp b/src/ChunkManager.hpp
index 73d90bc..2a8a049 100644
--- a/src/ChunkManager.hpp
+++ b/src/ChunkManager.hpp
@@ -15,9 +15,9 @@ public:
 };
 
 enum {
-    INSTANCE_OVERWORLD, // default instance every player starts in
-    //INSTANCE_IZ, // all infected zones share an instance
-    //INSTANCE_UNIQUE // fusion lairs are generated as requested (+ uid)
+    INSTANCE_OVERWORLD // default instance every player starts in
+    //INSTANCE_IZ, // these aren't actually used
+    //INSTANCE_UNIQUE
 };
 
 namespace ChunkManager {
diff --git a/src/NPCManager.cpp b/src/NPCManager.cpp
index 8a9f696..cd798b1 100644
--- a/src/NPCManager.cpp
+++ b/src/NPCManager.cpp
@@ -592,6 +592,8 @@ void NPCManager::handleWarp(CNSocket* sock, int32_t warpId) {
 
     MissionManager::failInstancedMissions(sock); // fail any missions that require the player's current instance
     
+    uint64_t fromInstance = plrv.plr->instanceID; // saved for post-warp
+
     if (plrv.plr->instanceID == 0) {
         // save last uninstanced coords
         plrv.plr->lastX = plrv.plr->x;
@@ -624,6 +626,18 @@ void NPCManager::handleWarp(CNSocket* sock, int32_t warpId) {
         plrv.plr->instanceID = INSTANCE_OVERWORLD;
         sock->sendPacket((void*)&resp, P_FE2CL_REP_PC_WARP_USE_NPC_SUCC, sizeof(sP_FE2CL_REP_PC_WARP_USE_NPC_SUCC));
     }
+
+    // post-warp: check if the source instance has no more players in it and delete it if so
+    if ((fromInstance >> 32) == 0)
+        return; // don't clean up overworld/IZ chunks
+
+    std::vector<std::tuple<int, int, uint64_t>> sourceChunkCoords = ChunkManager::getChunksInMap(fromInstance);
+    for (std::tuple<int, int, uint64_t>& coords : sourceChunkCoords) {
+        Chunk* chunk = ChunkManager::chunks[coords];
+        if (chunk->players.size() > 0)
+            return; // there are still players inside
+    }
+    ChunkManager::destroyInstance(fromInstance);
 }
 
 /*