Grenfell Tower: Here's What A Fire Scientist Thinks

By James O Malley on at

London woke up this morning to another tragedy. Overnight, the 24-storey Grenfell Tower near Ladbroke Grove caught fire and at the time of writing, there are over 50 people in hospital and 6 fatalities have been confirmed so far. Obviously the full story of what happened is not yet known, but the incident does raise a number of questions: What caused it? Could it happen again? What can we do to prevent future tragedies?

Dr Claire M Benson is a fire scientist in the Explosion & Fire Research Group at London South Bank University, and she was kind enough to answer our questions. Here's our Q&A:

Giz: What are the most common causes/risks of building fires like this?

Dr Benson: Obviously there are many things that can cause fires in domestic premises but the vast majority are accidental. The most common causes would be things like kitchen fires, electrical appliance fires, and smoking related incidents. Though I would say for an event like this the ignition source for me is secondary in importance to the fire spread factors, and ability to evacuate and fight the fire.

Giz: Are tower block fires something that happen often?

Dr Benson: Serious fires specifically like this are very rare though unfortunately they do seem to occur every few years. In recent years large scale fires, requiring high levels of brigade resources (more than 5 ‘pumps’ or fire appliances), have tended to be warehouses or rubbish or recycling sites.

Residential property fires of this severity are rare, mostly because generally the fire safety products and planning in the UK is usually so good. Lakanal House [in 2009] was a particularly bad fire that resulted in the death of 6 residents, though that wasn’t as large as the Grenfell Tower fire would appear to be. I think this may well be the worst incident we’ve seen in the UK in decades.

Giz: Presumably modern buildings are better designed to cope with fires than old ones - are there any new technologies and design techniques are used to safeguard against fire?

Dr Benson: It would depend on the design and build of the building. Fire safety is a holistic process that looks at:

  • Limiting igniton sources
  • Limiting fire spread opportunities - so the fire should not be able to spread through a building quickly. Materials have fire ratings and should be chosen specifically to prevent this. If reports of rapid fire spread in Grenfell are correct many questions will be asked about the materials used, and air flow e.g. were there gaps between floors or in the skin causing a chimney type effect that funnelled the flames upwards?
  • Enabling warning to building users as early as possible
  • Enabling safe and timely escape
  • Allowing emergency service access into to the building to rescue occupiers and fight the fire

All of this is designed first and foremost to save lives.

In England (it is slightly different in wales and Scotland) There is a massive set of rules in “approved document B” that covers what is required by law and gives advice about how to make all buildings.

New residential buildings over 30m are required to be fitted with sprinklers. That has not been applied to old buildings. Some new buildings, like the Shard, will also have fire evacuation lifts.

In terms of warning, evacuation and firefighting I would expect:

  • Working alarm systems that can be heard inside flats.
  • Protected corridors and emergency exits/ stairwell with fire doors as a minimum, and ideally in the stairwell positive pressure (i.e. you create pressure inside the stairwell so that if a door opens air pushes out rather than smoke entering. [This] enables people to get out, and firefighters to get in.)
  • Good compartmentation throughout to prevent the fire, or smoke from getting from one section of a floor to another, and from one floor to the next above. Doors and walls will be rated to prevent fire spread within e.g. half an hour. Gaps for cabling etc will be at a minimum. Gaps around those facilities will be filled with fire block type chemicals.
    Designated points inside the building where firefighters get a fire fighting water supply (e.g. dry risers - a empty pipe running up the building into which water can be pumped, and then can be picked up by firefighters further up the building).

Giz: What sort of evacuation plan will be in place for a building like this? There have been some reports that residents might have been told to stay in place and await rescue - is this better than trying to get out?

Dr Benson: This does depend on the building. Some buildings are designed with such good compartmentation, and such slow evacuation routes, that the advice is stay and let the firefighters come to you as you will be safe in the flats. According to the Fire Brigade Union representative this morning though the Fire Brigade’s ability to access the building and fight the fire seems to have been prevented for some reason.

Giz: There's speculation the tower could collapse: What are the key risks here? How could the fire cause this?

Dr Benson: Depends on the structure. If the main structure of the building is made of concrete/ metal I would be surprised if it collapsed, however this fire has burned for a number of hours so the heat would be considerable. It would depend on the thickness/ type of materials and sort of reinforcement they had.

Giz: How long will the investigation take? And what could this mean for the future?

Dr Benson: The investigation will require slow level-by-level, and layer-by-layer forensic, almost archaeological, assessment. It will be slow, and the fire could take days to put out fully, meaning it may not start soon.

For me the main point is that in the UK we have excellent fire safety products and rules. They could definitely be better, e.g. all building over 30m could have sprinklers as [the Building Research Establishment, the organisation that defines a number of construction standards] have shown it is not only safe but cost effective to install them. But we have enough safety regulations, products and information for events like this to never happen.

In my opinion it is highly likely some type of failure has happened for this to occur but whether that’s a direct failure, systemic or this is some sort of unforeseen fire phenomenon is hard to say. Lessons will have to be learned from this but it is way too early to apportion blame.

Our huge thanks to Dr Benson for speaking to us. We’ll add a donation link for those affected by the fire as soon as a verified donations page has been setup.

Picture credit for the photo at the top: Natalie Oxford.