Anaerobic Culture Tubes - These bacteria exist when the oil is stagnant. They reduce chemicals in the oil emulsion to give hydrogen sulphide which is the noxious 'Rotten Egg' smell given off when the oil is disturbed. They also give off acids which reduce the alkalinity of the emulsion and in certain cases promote corrosion. A separate test is required for both aerobic and anaerobic bacteria. (Initial readings after 24 hours incubation will show accurate higher levels of contamination - slight contamination may only show after 24 hours of incubation) All have a shelf life of 9 months. Each box of 10 contains full instructions, labels and expiry date. Incubators also available through this site.