I am working on performance review of sulphur recovery unit (SRU). Recently we conducted a performance test in SRU. In this regard I wish to know the correct method of measurement of sulphur recovery. Some people believe that sulphur recovery should be merely based on measurement of sulphur in feed minus that in incinerator stack whereas I strongly believe that sulphur balance must be carried out which includes sulphur in feed and stack plus the product sulphur recovered in pit/storage. Material balance is a key to any performance test of the plant. Hence I believe that product sulphur measurement in pit is essential for estimating the % sulphur recovery. Kindly confirm if my understanding is correct. Alternatively please advise other methods of sulphur recovery measurement and the most accurate method to be followed.