How did London tower block fire spread so fast and kill so many?
Guilhem Baker/LNP/Rex/Shutterstock By Feng Fu In the middle of the night, while most residents were sleeping, a devastating fire started at Grenfell Tower, a high-rise block of flats in London. At least 17 people have died, but the toll is expected to rise. A thorough investigation will doubtless uncover the cause. But that will take time and people are clamouring to know now how the firespread so rapidly and why residents found it so difficult to escape. From an engineering perspective, a number of factors in the design of the 24-storey tower may have contributed to the speed and scale of the blaze. Most of the current guidelines for high-rise structures across the world contain detailed design requirements for fire safety, such as evacuation routes, compartmentation and structural fire design. But Grenfell Tower was built in 1974. At that time, the rules and regulations were not as clear and well developed as they are now. The evacuation route is one of the most important design elements when it comes to fire safety. It should allow occupants to escape as quickly as possible, while sheltering them from smoke and flames. Some tall buildings have staircases on the outside to prevent people from getting stuck in the corridors and provide access to fresh air while they escape. Other options include installing high-power fans inside buildings, to clear the evacuation route of smoke in the event of a fire. This feature is included in the design of Dubai’s Burj Khalifa, the tallest building in the world. It’s clear that residents of Grenfell were not happy with the fire safety of the escape route from a blog posted in November 2016 and the design would suggest there was only one set of stairs for evacuation. Investigators will need to determine what evacuation routes were available. Another key strategy is to include fire compartments to stop the fire spreading quickly. This involves barriers in the building – such as fire-resistant doors and walls – to confine a fire, or at least slow the speed at which it can spread. The design of these compartments vary according to whether the building is intended for residential or commercial use. Some buildings even include special measures for fires, such as refuge rooms for occupants in the higher storeys, who could have trouble escaping down stairs. There are also active fire protection methods such as sprinklers. A parliamentary report recommended that sprinkler systems be installed in tower blocks across the UK after another high-rise fire in London in 2009 at Lakanal House in Camberwell, in which six people died. But it’s not clear that these measures were implemented in Grenfell Tower. A local residents action group also claimed that their warnings about a lack of fire safety measures “fell on deaf ears”. The fire risk level of any building also depends on its structural design – that is, the capacity of its materials to resist fire. Different materials receive different fire ratings. For example, steel buildings are normally required to have structural elements such as beams or columns that can stand for one to two hours with the help of fire protection material such as intumescent paint, which swells up when heated to protect the material beneath. According to reports, the key structural components of Grenfell Tower were mostly made of concrete – a material which rates highly for fire resistance. While other materials can buckle in high temperatures, concrete structures can help to prevent building collapse in case of fire, as well as making it safer to use helicopters – which can dump up to 9842 litres of water at a time – to extinguish a blaze. There were also reports relating to cladding added as part of an £8.7 million refurbishment in 2016. The material used was primarily aluminium, which is not fire resistant. What’s more, aluminium has high thermal conductivity – so the cladding itself could have heated up very quickly, failing to prevent the fire from travelling through the windows and up the exterior of the block from one storey to another. In truth, most old buildings do not conform to the latest guidelines for fire safety design, so it is imperative to update them by installing sprinklers, fire alarms and extra fire evacuation staircases. While those affected may have to wait for some time before the causes of this tragedy become clear and responsibility is taken, landlords and local councils can act now to help prevent another disaster of this scale from happening again. This article was first published by The Conversation More on these topics: