In a fine chemicals plant, an operator is collecting a sample of distilled toluene (C6H5-CH3, aromatic hydrocarbon classified as harmful and highly flammable, often used as a solvent) in a tank to check its purity when the collecting vessel suddenly ignites. The vessel remains attached to the flange of the tank’s bottom valve, but the operator hits it while trying to get away and a pool of burning toluene falls on the ground. The operator closes the bottom valve manually and the automatic valve connected to the first. He raises the alarm so that the workshop is evacuated . An internal response team fight the fire with a powder fire extinguisher and cools the equipments of the workshop (tank, valves …). Nobody had been injured and no impacts on the environment are reported, the activity resumes normally .

The investigation led by the operator shows that the toluene was charged with static electricity due to the motion of the product during sampling and contacts of the solvent with the aqueous phase of the sample. The electrostatic charge has been accumulated in the product due to the insulation of the collecting vessel. In contact with a conductive element of an equipment, probably the flange of the stainless steel bottom valve, an electrostatic discharge occurred and ignited the vapors of toluene.

As a feedback, the operator:

• Reviews the methods for sampling product so that a confined system from the top of the equipment is used and plans the purchase of additional sampling system of this kind
• Defines specific procedures when sampling from the top is impossible, due to technical or product quality constraints
• checks systematically the ground connection of the collecting vessels before sampling operations
• Reminds the safety procedures to the operators to reduce the risks associated with static electricity
• Looks for new sampling method for solvent’s tanks, to eliminate the falling of the solvent from the bottom of the tank to the collecting vessel