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Hello, this is the Grenfell Tower Inquiry podcast, reporting every day the inquiry sits.

I'm Eddie Mayer, and today's witness was Professor David Purser.

He's an inhalation toxicologist and fire specialist,

who's been asked to look into the causes of incapacitation and death at Grenfell.

He's also looked at the toxicity of materials in the tower.

And so I really need to know how this smoke once formed, either inside or outside the tower,

has moved in and around the flats and the various spaces in the tower with time.

And I'm particularly concerned about when the smoke got into the lobbies at Grenfell on different floors,

because this, I feel, was a key stage in the incident.

David Perser told the inquiry that it's almost impossible to recreate the exact smoke conditions at Grenfell,

so he's based his evidence on a wider understanding of fires in other multiple occupancy buildings.

Referring to a graph, he explained the importance of the time between people first being

alerted to a fire and their escape.

And generally speaking, if people start to be alerted and warned early on and they start to

move early on, there's usually a sort of golden early period during any fire when people can make a safe escape.

The problem with fires, as illustrated by this curve here, is that they tend to, the rate of which they get worse,

tends to get exponentially greater. So if you delay, then you get caught by this time, period

when the conditions can very, very rapidly deteriorate. Professor Pursa said there are three

hazards he's looked at, the visibility and density of the smoke, asphyxating gases, and heat.

He told the inquiry people can actually withstand smoke of quite a high temperature.

At 200 degrees centigrade in air, it's possible for volunteers to tolerate that for several minutes before they start to feel

...