On 13 February 2008, four men died in a 6.5m underground molasses tank in India. One of the men entered to check the how much product was in the tank. After 10 minutes he did not exit and did not respond to calls from above. A second man entered the tank and a short time latter stopped responding. Two more men entered the tank and they also collapsed.
Witnesses above described a foul stench from the tank. The newspapers reported that the likely contaminant was methane. Methane is odourless, so it is likely that hydrogen sulphide was also present. These fatalities could have been simply prevented if the contents of the tank were measured from above.
Source and picture: Telegraph - India