Interesting calls - March 2012

Exploding vacuum cleaner

NCEC recently received a call from a HazMat Officer at a metal tooling factory where a vacuum cleaner used for collecting metal powders had exploded, causing second degree burns to the operative who was subsequently hospitalised. The caller wanted to know what had caused the explosion and how to deal with the vacuum cleaner.

Our Emergency Responder advised the HazMat Officer that metal powders, such as aluminium and titanium, can form explosive mixtures in air and can react with water to produce explosive hydrogen gas. Prior to the arrival of the emergency services, the casualty's colleague had poured water into the vacuum cleaner and the contents were continuing to react and produce a gas. Our Emergency Responder advised the caller that the gas was most likely to be hydrogen and that the area should be well ventilated to prevent an explosive atmosphere. The use of dry extinguishing agents and quenching quantities of water were discussed, but ventilation was thought to be the most appropriate course of action.

NCEC's chemists understand the dangers of hazardous materials and are able to determine the products of reaction, whether that is with firefighting media or other chemicals. You can rely on our experience and expertise.

Exploding fridge freezer

NCEC recently received a call from a Fire Service Incident Commander who was trying to ascertain the cause of an exploding fridge-freezer at a domestic property.

After determining the details of the incident, including the type of appliance and refrigerant gas involved, our Emergency Responder suggested that either the system had over pressurised or a leak had been ignited. There were no scorch marks or combustion residues suggesting that the appliance had over pressurised, but the plastic food wrappers inside the fridge appeared shrunken and stiff, as if exposed to heat. The refrigerant gas was pentane and our Emergency Responder explained that it would burn cleanly and easily at low concentrations (flashpoint -49C, explosive limits 1.5 to 7.8% in air) suggesting that a leak ignited by the thermostat or other ignition source was the likely cause of the explosion.

Our Emergency Responders are available to discuss unusual incidents and can draw on their diverse range of expertise. Remote from the scene, they are able to research the problem and précis the results for you over the phone.

Leak at a COMAH-regulated site

Between 500 and 1,000 litres of molten phthalic anhydride was leaking at a COMAH site and the fumes were drifting off site. The HazMat Officer at the scene wanted advice about suitable isolation distances due to the proximity of residential and commercial properties.

Our Emergency Responder advised the caller that molten phthalic anhydride produces harmful and sensitising fumes, and recommended an initial isolation distance of 50 metres in all directions, and 300 metres downwind. Because the local weather conditions were cold and dry with not much wind, the Emergency Responder advised the caller that the fumes would stay close to the ground and would not dissipate readily. It was decided that people should be told to remain indoors with their windows and doors closed, rather than evacuate. The leaked material was covered in a foam blanket and a water curtain was set up downwind of the leak to reduce the fumes going off site.

NCEC's Emergency Responders use a wide range of reference materials, including Chemdata, to provide comprehensive advice in the event of an incident. The UK emergency services rely on our expert advice to protect people, property and the environment.