| Bulk transport containers used for flammable, corrosive and toxic liquids and gases will normally have a pressure/vacuum relief valve fitted to prevent damage to the tank from changes in the internal pressure. These valves should be inspected and maintained in line with the manufacturers instructions. Following a road incident in April 2020, investigations by Cleveland Police and HSE found evidence that a pressure/vacuum relief valve had undergone an unauthorised modification by a third party which prevented the valves safe operation View thesafety alert for full details. | 
