Tense moments at the Politecnico di Milano, Via Mancinelli Campus, where the rupture of a refrigerator in a chemistry laboratory triggered an alarm. Inside were about five grams of diazonium salts, unstable and potentially explosive substances. The area was evacuated and secured by firefighters and the NBCR unit, with the support of the bomb squad, which detonated the material. This is the second incident in a few days: on June 8, a researcher lost her thumb when an ampoule containing hypophosphorous acid and nitrogen salts exploded. Diazonium salts, used in various industries, are dangerous because of their thermal and mechanical instability: they can explode with heat, shock or even during drying.