Government tests on cladding involve burning a small sample of the material in a pure oxygen atmosphere, the Department for Communities and Local Government (DCLG) has said.
In the tests, the sample of the panel is burned in pure oxygen with a device called a bomb calorimeter.
DCLG said this was to test compliance with the “limited combustibility” element of buidling regulations guidance.
Cladding has been partly blamed by the Met Police for the spread of the Grenfell Tower fire, which killed at least 80 people two weeks ago.
Aluminium melts quickly in high temperatures, revealing the plastic core of a cladding panel, and so the flammability of that core can have significant consequences in a fire.
A DCLG spokesperson said: “Independent experts have provided advice on how to carry out a test that will show whether a panel is likely to meet the requirement of limited combustibility set out in Building Regulations guidance. The Building Research Establishment has adopted that approach in the tests now being conducted.”
Tests are not being carried out on insulation installed behind cladding, despite the Met Police revealing that the insulation on Grenfell Tower – as well as the cladding – has failed fire safety tests.
Last night David Orr, chief executive of the National Housing Federation, called on the government to halt the testing, as it was “now conclusive”, and “shift its focus to making people safe”.