What was found
ON RETURN FROM RECEIVING HOSPITAL TO BASE, DETECTED SULFUROUS FUMES. NO SECONDARY INDICATIONS. LANDED AT OUR BASE. NOTIFIED DISPATCH THAT OUR AIRCRAFT WAS OUT OF SERVICE AND CALLED OUR DUTY MECHANIC. INSPECTION OF AIRCRAFT REVEALED FUMES WERE COMING FROM LEAD ACID BATTERY IN NOSE COMPARTMENT OF AIRCRAFT. BATTERY WAS REPLACED, GROUND CHECKED, RETURNED TO SERVICE.