It sounds like a biological hazard from a movie blockbuster, but “kerosene fungus” - the presence of microbes in aviation fuel – was first identified as a problematic contaminant by the British and American air forces in the 1950s.

According to Royal Aeronautical Society Journal papers at the time, it was known that microbial growth caused problems such as fuel pump failures and corrosion, filter clogging and fuel tank corrosion, all obvious safety issues.

The problem came to Shell Aviation’s attention in the early 1960s, with airlines in Asia reporting fuel contamination issues. Shell experts travelled to the region to investigate. Airfield fuel storage and handling procedures were thoroughly tested and appeared clear of contamination, so the search was widened to extensive sampling of aircraft fuel tanks and filters in the region, as well as storage tanks, dispensers, and refineries from all over the world. The samples went to Shell’s Central Laboratories at Egham in southern England.

Technicians cultured each fuel sample in a medium that promoted microbiological growth. Half of the samples showed fungal growth, with random global distribution. The next challenge was to identify the fungus. Shell turned to The Commonwealth Mycological Institute at Kew in London, which identified the fungus as Cladosporium Resinae de Vries, a common species usually found living on creosoted telegraph poles and common throughout the world.

Shell already knew that the Cladosporium could thrive on aviation fuel but as it spores were airborne, there was no practical way to keep them out of fuel tanks. The answer to the presence of fungal contamination in the fuel actually lay in the presence another substance, water, as the Cladosporium could not grow without water, so could only thrive in fuel tanks where it was present. Water was already known as a potentially dangerous contaminant in fuel, due to the potential for ice to form at low temperatures, potentially leading to possible engine damage and failure. The warning for the aviation industry was clear – redouble efforts to combat water contamination.

Shell had been active in the area of managing water contamination since it had been identified as an issue in the early days of aviation. The Shell Water Detector, a simple and economical device for sampling fuel to detect water, was introduced in 1957. It soon became the industry standard and is still the aviation sector’s system of choice for detecting water today.

Shell Aviation also helped manage another biological safety hazard in more recent times. In 2020 up to 80% of the world’s aircraft were grounded due to COVID-19, with fuel left in aircraft wing tanks. This created the problem of monitoring and managing the fuel to prevent microbe contamination, which if unchecked could lead to defuelling and clean-up, or worse, airframe corrosion and blocked fuel systems. Shell provided advice and support to airlines around the world to help manage the issue and protect aircraft during this enforced lay-off.

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