diff --git a/apps/opencs/model/tools/bodypartcheck.cpp b/apps/opencs/model/tools/bodypartcheck.cpp
index f1f898440..da7fe7b57 100644
--- a/apps/opencs/model/tools/bodypartcheck.cpp
+++ b/apps/opencs/model/tools/bodypartcheck.cpp
@@ -33,7 +33,7 @@ void CSMTools::BodyPartCheckStage::perform ( int stage, Messages &messages )
     if ( bodyPart.mData.mVampire < 0 )
         messages.push_back(std::make_pair( id, bodyPart.mId + " has negative vampire flag." ));
 
-    if ( bodyPart.mData.mFlags < 0 || bodyPart.mData.mFlags > 2 )
+    if ( bodyPart.mData.mFlags < 0 || bodyPart.mData.mFlags > 3 )
         messages.push_back(std::make_pair( id, bodyPart.mId + " has out of range flags value." ));
 
     if ( bodyPart.mData.mType < 0 || bodyPart.mData.mType > 2 )
@@ -52,4 +52,4 @@ void CSMTools::BodyPartCheckStage::perform ( int stage, Messages &messages )
         messages.push_back(std::make_pair( id, bodyPart.mId + " has no race." ));
     else if ( mRaces.searchId( bodyPart.mRace ) == -1 )
         messages.push_back(std::make_pair( id, bodyPart.mId + " has invalid race." ));
-}
\ No newline at end of file
+}
diff --git a/components/esm/aipackage.hpp b/components/esm/aipackage.hpp
index 8a31aadf5..cbe82f16e 100644
--- a/components/esm/aipackage.hpp
+++ b/components/esm/aipackage.hpp
@@ -16,8 +16,10 @@ namespace ESM
 
     struct AIData
     {
-        // These are probabilities
-        char mHello, mU1, mFight, mFlee, mAlarm, mU2, mU3, mU4;
+        unsigned char mHello;
+        char mU1;
+        unsigned char mFight, mFlee, mAlarm; // These are probabilities [0, 100]
+        char mU2, mU3, mU4; // Unknown values
         int mServices; // See the Services enum
 
         void blank();
diff --git a/components/esm/loadarmo.hpp b/components/esm/loadarmo.hpp
index 991f4e185..6be9dd971 100644
--- a/components/esm/loadarmo.hpp
+++ b/components/esm/loadarmo.hpp
@@ -46,7 +46,7 @@ enum PartReferenceType
 // Reference to body parts
 struct PartReference
 {
-    char mPart;
+    unsigned char mPart; // possible values [0, 26]
     std::string mMale, mFemale;
 };
 
diff --git a/components/esm/loadbody.hpp b/components/esm/loadbody.hpp
index 286e3f96e..5e9869d24 100644
--- a/components/esm/loadbody.hpp
+++ b/components/esm/loadbody.hpp
@@ -49,10 +49,10 @@ struct BodyPart
 
     struct BYDTstruct
     {
-        char mPart;
-        char mVampire;
-        char mFlags;
-        char mType;
+        unsigned char mPart; // mesh part
+        unsigned char mVampire; // boolean
+        unsigned char mFlags;
+        unsigned char mType; // mesh type
     };
 
     BYDTstruct mData;
diff --git a/components/esm/loadnpc.hpp b/components/esm/loadnpc.hpp
index fd3e45bdc..0e90108c3 100644
--- a/components/esm/loadnpc.hpp
+++ b/components/esm/loadnpc.hpp
@@ -80,10 +80,12 @@ struct NPC
              mPersonality,
              mLuck;
 
-        char mSkills[Skill::Length];
-        char mReputation;
+        // mSkill can grow up to 200, it must be unsigned
+        unsigned char mSkills[Skill::Length];
+
+        char mFactionID;
         unsigned short mHealth, mMana, mFatigue;
-        char mDisposition, mFactionID, mRank;
+        signed char mDisposition, mReputation, mRank;
         char mUnknown;
         int mGold;
     }; // 52 bytes
@@ -91,9 +93,10 @@ struct NPC
     struct NPDTstruct12
     {
         short mLevel;
-        char mDisposition, mReputation, mRank;
+        // see above
+        signed char mDisposition, mReputation, mRank;
         char mUnknown1, mUnknown2, mUnknown3;
-        int mGold; // ?? not certain
+        int mGold;
     }; // 12 bytes
 
     struct Dest
@@ -103,7 +106,7 @@ struct NPC
     };
     #pragma pack(pop)
 
-    char mNpdtType;
+    unsigned char mNpdtType;
     NPDTstruct52 mNpdt52;
     NPDTstruct12 mNpdt12; //for autocalculated characters
 
diff --git a/components/esm/loadregn.hpp b/components/esm/loadregn.hpp
index 1992c951b..c231b6aa0 100644
--- a/components/esm/loadregn.hpp
+++ b/components/esm/loadregn.hpp
@@ -24,10 +24,11 @@ struct Region
 #pragma pack(1)
     struct WEATstruct
     {
-        // I guess these are probabilities
-        char mClear, mCloudy, mFoggy, mOvercast, mRain, mThunder, mAsh, mBlight,
+        // These are probabilities that add up to 100
+        unsigned char mClear, mCloudy, mFoggy, mOvercast, mRain, mThunder, mAsh, mBlight,
         // Unknown weather, probably snow and something. Only
         // present in file version 1.3.
+        // the engine uses mA as "snow" and mB as "blizard"
                 mA, mB;
     }; // 10 bytes
 
@@ -35,7 +36,7 @@ struct Region
     struct SoundRef
     {
         NAME32 mSound;
-        char mChance;
+        unsigned char mChance;
     }; // 33 bytes
 #pragma pack(pop)