A chemist believes his experiment could explain why cladding on high rise towers was found to be a fire risk after the Grenfell blaze, despite having been previously deemed safe.
Professor Laurence Harwood found that aluminium cladding panels, heated to more than 300 C, would ignite simply from having water sprayed on to it.
The insulating foam underneath such panels could absorb water over time, meaning the fire risk of cladding could grow after they were installed, he said.
Prof Harwood added this could explain why cladding removed from buildings after the Grenfell fire failed flammability testing but the individual parts were deemed safe by their manufacturers.
The cladding on the Grenfell Tower helped spread the blaze that gutted the 24-storey building and killed at least 80 people, witnesses to the tragedy have said.
Prof Harwood has sent his findings to Sir Martin Moore-Beck, who is chairing the inquiry into the fire.
The reaction he identified also produced more heat as well as hydrogen, which itself burns violently produce more heat and water, in the form of steam.
Prof Harwood said: “I was genuinely taken aback the first time I tested my proposal in the laboratory. I wasn’t expecting such an intense reaction when I sprayed water onto a panel that I had heated with a blow torch.
“The presence of water absorbed by the polyisocyanurate foam, over a lengthy period of exposure to the elements, could play a significant role in accelerating a cladding fire by causing hot aluminium to react violently, generating heat and hydrogen.
“The latter would then burn violently to produce more heat and steam, which would then allow polyethylene inner layers to be exposed over a large surface area, in turn burning to produce more heat and more steam, setting up a feedback loop and causing a runaway fire.”
Prof Harwood, who is director of the Chemical Analysis Facility at the University of Reading, carried out the tests at the request of the BBC South’s Inside Out programme, which will air a programme about the results on Monday night.
The programme makers wanted to learn how the cladding on high-rise buildings in Portsmouth could be de deemed a fire risk having passed safety tests.