Posted By Clarke Kent A client was asked to remove an underground diesel tank that had been uplifted and foam filled approximately 12 months prior. It is company procedure to have explosimeters present and switched on at all times when operating in or near potential explosive atmospheres. The explosimeters are calibrated to measure the pentane levels in petrol vapour as this is their main use. When the fill pipes were removed the explosimeter went off and work stopped. After consultation with the company responsible for the foam filling they claim that the formaldehyde resin in the foam could have triggered the explosimeter.I appreciate that under normal conditions diesel would not produce an explosive atmosphere. So my question is could the formaldehyde be responsible or do we need to recalibrate the explosimeter for diesel. Get your thinking caps on!