diff --git a/src/game/server/swarm/asw_radiation_volume.cpp b/src/game/server/swarm/asw_radiation_volume.cpp
index cd5db90b8..97c96aede 100644
--- a/src/game/server/swarm/asw_radiation_volume.cpp
+++ b/src/game/server/swarm/asw_radiation_volume.cpp
@@ -44,7 +44,7 @@ void CASW_Radiation_Volume::Spawn( void )
 	AddEffects(EF_NODRAW);
 	SetSolid( SOLID_BBOX );
 	float boxWidth = m_flBoxWidth;
-	UTIL_SetSize(this, Vector(-boxWidth,-boxWidth,0),Vector(boxWidth,boxWidth,boxWidth * 2));
+	UTIL_SetSize( this, Vector( -boxWidth, -boxWidth, 0 ), Vector( boxWidth, boxWidth, boxWidth * 2 ) );
 	SetCollisionGroup(ASW_COLLISION_GROUP_PASSABLE);	
 	AddSolidFlags(FSOLID_TRIGGER | FSOLID_NOT_SOLID);
 	SetTouch( &CASW_Radiation_Volume::RadTouch );
@@ -61,25 +61,67 @@ bool CASW_Radiation_Volume::IsValidRadTarget( CBaseEntity *pOther )
 	return pOther->IsNPC();
 }
 
-void CASW_Radiation_Volume::RadTouch( CBaseEntity *pOther )
+// Helper centralizing detection logic used by RadTouch and RadTouching
+bool CASW_Radiation_Volume::IsInRadiationVolume( CBaseEntity *pEnt )
 {
-	// if other is a valid entity to radiate, add it to our list
-	if (IsValidRadTarget(pOther) && m_hRadTouching.Find(pOther) == m_hRadTouching.InvalidIndex())
+	if ( !pEnt )
+		return false;
+
+	// m_flBoxWidth used as radius:
+	const float flRadius = m_flBoxWidth;
+	const float flRadiusSqr = flRadius * flRadius;
+
+	const Vector vecCenter = GetAbsOrigin();
+	CCollisionProperty* pEntColl = pEnt->CollisionProp();
+	CCollisionProperty* pVolColl = CollisionProp();
+	if ( !pVolColl )
+		return false;
+
+	// compute the nearest point on the other entity to our center (robust for large NPCs)
+	Vector vecNearest;
+	if ( pEntColl )
+		pEntColl->CalcNearestPoint( vecCenter, &vecNearest );
+	else
+		vecNearest = pEnt->WorldSpaceCenter();
+
+	// If other is a marine, use CYLINDER test:
+	// - horizontal (XY) distance < radius
+	// - AND the nearest point must be within our cuboid bounds (so Z is constrained by the volume)
+	if ( pEnt->Classify() == CLASS_ASW_MARINE )
 	{
-		m_hRadTouching.AddToTail(pOther);
-		if (GetNextThink() == TICK_NEVER_THINK)
-			SetNextThink( gpGlobals->curtime );
+		// must be inside vertical bounds (cuboid)
+		if ( !pVolColl->IsPointInBounds( vecNearest ) )
+			return false;
+
+		// horizontal delta (XY)
+		Vector vecDelta = vecNearest - vecCenter;
+		// horizontal distance squared check (circle)
+		if ( ( vecDelta.x * vecDelta.x + vecDelta.y * vecDelta.y ) >= flRadiusSqr )
+			return false;
+
+		return true;
 	}
+	// aliens: full cuboid
+	return pVolColl->IsPointInBounds( vecNearest );
 }
 
-bool CASW_Radiation_Volume::RadTouching(CBaseEntity *pEnt)
+void CASW_Radiation_Volume::RadTouch( CBaseEntity* pOther )
 {
-	if (!pEnt || !pEnt->CollisionProp() || !CollisionProp())
-		return false;
+	// if other is a valid entity to radiate, add it to our list
+	if ( !IsValidRadTarget( pOther )
+		|| m_hRadTouching.Find( pOther ) != m_hRadTouching.InvalidIndex()	// avoid duplicates
+		|| !IsInRadiationVolume( pOther ) )
+		return;
 
-	Vector vecNearest;
-	pEnt->CollisionProp()->CalcNearestPoint( GetAbsOrigin(), &vecNearest );
-	return CollisionProp()->IsPointInBounds(vecNearest);
+	m_hRadTouching.AddToTail( pOther );
+	if ( GetNextThink() == TICK_NEVER_THINK )
+		SetNextThink( gpGlobals->curtime );
+}
+
+bool CASW_Radiation_Volume::RadTouching( CBaseEntity* pEnt )
+{
+	// simply reuse centralized detection
+	return IsInRadiationVolume( pEnt );
 }
 
 void CASW_Radiation_Volume::RadHurt(CBaseEntity *pEnt)
@@ -90,7 +132,7 @@ void CASW_Radiation_Volume::RadHurt(CBaseEntity *pEnt)
 	int iDamageType = DMG_RADIATION;
 
 	CBaseEntity *pAttacker = this;
-	if (m_hCreator.Get() && pEnt->Classify() != CLASS_ASW_MARINE)	// don't deal friendly fire damage from rad barrels
+	if (m_hCreator.Get() && pEnt->Classify() != CLASS_ASW_MARINE) 	// don't deal friendly fire damage from rad barrels
 		pAttacker = m_hCreator.Get();
 
 	CBaseEntity *pWeapon = NULL;
diff --git a/src/game/server/swarm/asw_radiation_volume.h b/src/game/server/swarm/asw_radiation_volume.h
index 561b92d14..86611b082 100644
--- a/src/game/server/swarm/asw_radiation_volume.h
+++ b/src/game/server/swarm/asw_radiation_volume.h
@@ -13,6 +13,8 @@ class CASW_Radiation_Volume : public CBaseEntity
 	void RadHurt(CBaseEntity *pEnt);
 	bool RadTouching(CBaseEntity *pEnt);
 	bool IsValidRadTarget( CBaseEntity *pOther );
+	// helper that centralizes the collision/volume checks used by RadTouch and RadTouching
+	bool IsInRadiationVolume( CBaseEntity *pEnt );
 	
 	DECLARE_DATADESC();
 	CUtlVector<EHANDLE> m_hRadTouching;