Hong Kong high-rise fire: Expert explains why blaze spread so quickly

Firefighters are still battling hot spots after a massive fire raged through a Hong Kong high-rise complex. At least

44 people have died, including a firefighter, while dozens more remain in hospital and more than 200 still unaccounted for. Authorities say the

unaccounted for. Authorities say the blaze spread rapidly from building to building. Police have arrested three men

building. Police have arrested three men over alleged negligence. Nearly a

thousand people displaced by the disaster are seeking refuge at temporary shelters.

Let's speak to Dr. Anoir Arabi, lecturer in fire safety engineering at the University of Queensland. He has several years of teaching and academic experience in Hong Kong. Dr. Arabi,

thank you for making the time to speak with us. The cause of this blaze still

with us. The cause of this blaze still uncertain, but looking at the scale and speed at which the fire spread through the estate. What will authorities be

the estate. What will authorities be looking at?

>> So, um, thank you first of all for having me. Uh yes indeed we don't know

having me. Uh yes indeed we don't know the source of ignition but as you have mentioned it might not matter so much what started the fire but what's really

important here is why did it spread so fast in high-rise buildings what we try to do is we try to ensure that if there is a fire it remains contained within a

compartment so that the fire can stay within this compartment for the entire duration until it gets extinguished either due to burnout or due to

firefighter intervention. What happened

firefighter intervention. What happened here? Um I after talking to many of my

here? Um I after talking to many of my colleagues in in the field as well is because of this u scaffolding on the

outside that completely negated the effect of compartmentation. So the fire had a had a way to travel from one floor to the other uninterrupted

the inside the building. Normally, when

it's not under renovation, we we even seal even the ducts that allow wires to go through because we want to prevent any fire. But when you have a flammable

any fire. But when you have a flammable uh scaffolding on the outside, that that completely um makes the entire point moved.

>> This scaffolding, this is Hong Kong's signature bamboo scaffolding and netting. So, could this have been a key

netting. So, could this have been a key reason why the fire spread to so many apartment blocks in the complex so quickly when you know they use fire retardant on the netting or they they do

take measures in this case to prevent fires from spreading. So, what would have happened in this situation?

>> This is such a such a fantastic point.

Thank you for bringing it up. So nothing

is really fireproof. Uh if any if something has

fireproof. Uh if any if something has carbon in it even with fire retardants with provided it has sufficient heat flux applied to it then it will burn. It

doesn't have to start with the bamboo.

It can be it can be any small localized fire and if that supplies sufficient heat for a sufficient duration to the scaffolding that will um or to the

material that's applied that may uh overcome fire the effect of fire retardants and in the end bamboo is a natural material. It's it's a it's a

natural material. It's it's a it's a wood. It's a timber. So it's it's it's

wood. It's a timber. So it's it's it's basically made out of sugars and polymers all of which um are combustible. So when you sub subject

combustible. So when you sub subject that bamboo to a high enough heat flux again for a sufficient duration it will ignite. So um so

ignite. So um so the fact that it hasn't happened to this scale before or we've seen them actually

happening more often recently it's just that this time um it just happened to be at at a at a scale that is um many are

comparing to Grimfell in other when you look at the pictures how it spread to between buildings it's even worse some of my colleagues have called it a wildland urban fire. So, it's the same

as a forest fire, how the fire spreads between trees.

>> So, does this then come down to fire safety of the renovation works? Were

there appropriate measures in place for these buildings that were under renovation?

>> As I understand, uh, bamboo scaffolding is being phased out.

Um, last I checked with my colleagues in Hong Kong. Um and it is due to this kind

Hong Kong. Um and it is due to this kind the concerns about its fire safety as one of the reasons for that. Um

so when you have the renovations taking place like this uh the building is it is at its most vulnerable really uh because

it is a flammable scaffolding and I'm not sure anywhere else in the world uses a flammable scaffolding like Hong Kong does at least not at the scale that Hong

Kong does. Having lived in Hong Kong, um

Kong does. Having lived in Hong Kong, um we need to build at a scale to accommodate the population that no other place in the world needs to build at

almost. Um so we get these buildings

almost. Um so we get these buildings very very close proximity to each other.

Um we we need to accommodate all the people. So we keep trying to build

people. So we keep trying to build higher and higher and closer to each other to make use of the limited land resources that we have. If you know about um in in Hong Kong, housing is

such a big issue, you can you when children are born, as soon as they are 18 years old, they have to register if they want to get a foot in into into the

public housing that's available given that Hong Kong has the world's um most u uh expensive real estate. And and so

what happens is you have families living in very small spaces with lots and lots of fuel accumulating because of so many people living in small space um that

every apartment actually becomes it's um it's so full of fuel that it is able to burn and generate heat that continues to um

propagate the fire. And as we've seen for example in the Grenell fire uh when it's when the fire is outside and spreading vertically that's that's how fire likes to spread because of

buoyancy. So the fire will tilt and will

buoyancy. So the fire will tilt and will touch the solid causing the solid to degrade and release combustible gases that will allow it to spread. So the

fact that we see it spreading vertically um in such a fast pace is to me to be honest not very surprising. Although the

fact that it happened um is really unfortunate.

>> You made the key point about the fire spreading vertically. It spreads so

spreading vertically. It spreads so quickly and firefighters had said they had a really difficult time getting to the top floors of those buildings. When

it comes to fire safety, when it comes to situations like this, when a fire is spreading so quickly, what needs to be done to help get people out as quickly as possible or what systems need to be

in place to prevent it from happening that people get trapped that there's reports that more than 200 are still unaccounted for and may be trapped in the upper floors of those buildings.

>> Indeed. Um, and this is another really important point. Thank you for bringing

important point. Thank you for bringing it up. So when we design buildings for

it up. So when we design buildings for fire safety, we work in what's called the fire safety strategy. So we bring in the goal is to bring in all the

components that we can work with to ensure we achieve the objectives of everyone getting out safe and sometimes we have secondary objectives like

protection of property. So uh usually in high-rise buildings what we do is we do a stage evacuation. So when there is

a fire on a specific floor you evacuate that floor and sometimes one or two or three floors above and below it at the same time. So that you ensure that there

same time. So that you ensure that there the people are able to use the stairs without having congestion without uh without having crush because you and you

don't also want to keep the stair the fire doors at the stairs open for too long because you don't want smoke to come in and you don't want the pressurization inside the stairs to go

to go um uh if you open too many doors then you're basically poking holes in a balloon in many stages you lose pressure. So you don't want to do that

pressure. So you don't want to do that either. Um, so all of this is under the

either. Um, so all of this is under the assumption that the fire is not going to spread vertically. So we try our best to

spread vertically. So we try our best to make sure to limit that vertical spread as much as practically possible. That's

why here in Australia for example and again after the Grimfell fire um there is such a push to look at building facads and ensure that these building

facads are to as much as practical non-combustible and if they are combustible that fire would not spread at a rate that would compromise occupant

safety. But again once you that that's

safety. But again once you that that's for the building. Once you put something on the outside of the building, you wrap the building with um some of my friends or some of my colleagues have called it

an external facade or an added facade that um doesn't matter what you do uh because you haven't designed for a

scenario like this which completely um throws off uh your strategy to begin with. I want to go back to an earlier

with. I want to go back to an earlier point you made about how densely populated Hong Kong is and so because land resources are limited, a lot of buildings are built very high. These

these buildings in this complex were about 31 stories high. So in terms of very tall building structures, what measures need to be put in place to

ensure fire safety, especially for those living at the top?

>> Very very good point. Um so

so there is the the building design needs to be um uh needs to account for all the occupants escaping and we

already do that. So we we try to we do calculations on how many people are going to be in the building, how long it takes them after they hear the fire

alarm to actually spring into action and then how long it takes them to get from their apartment to the stairs and then how long it takes them to go down. Um uh

so that's that's one thing. The next

thing is to ensure that there is not going to be either horizontal or lateral flame spread. So you don't want the fire

flame spread. So you don't want the fire to spread horizontally on the floor. So

you make sure for example the doors are fire rated so that if there is a fire in an apartment it will stay within the apartment. The building occupants will

apartment. The building occupants will or the apartment occupants will escape the the door will close and then the fire will just stay within that. So you

make sure that the u the door can't sustain a fire for a specific duration.

Same for the walls and the wind and and and the windows and the facade. Now if

the fire were to spread then by that time that it manages to breach that compartmentation people would have already escaped. So

people on the fire floor and the floor below will have already escaped. They'll

be fine. Um at least that's the idea in principle. Now for vertical spread which

principle. Now for vertical spread which is perhaps the worst case uh you ensure that there is no combustible facade on the outside of the building or no

continuous facade combustible facade. If

there is a fire that's coming out of the windows or anything, it doesn't burn the facade. It doesn't cause the facade to

facade. It doesn't cause the facade to ignite and then pro proceed to um spread fire vertically. What if the fire was

fire vertically. What if the fire was inside the apartment? Well, you don't want any penetration between your floor and above floor. So if there's cables or

if there is plumbing and even horizontally not necessarily only vertically you you seal those um you seal those penetrations so that the fire

is not able to escape and all of this uh relies on using of course um I would I

would venture to say certified um materials and components and systems that have been tested under specific conditions to meet some specific uh

recommendations for or some specific requirements for fire safety. So the

door for example after after a set period of time if you touch it on the outside even if there is a fire it shouldn't you shouldn't feel any heat.

Same for structural members. The

structural members particularly in tall buildings need to be designed such that the fire won't affect their structural stability which can be which can be a

huge problem as we had seen in um in in the World Trade Center collapse disasters as well or um terrorist events

um and and so that's also a very very important thing to do. And in Hong Kong, they have a very strict regulatory environment that tries to ensure that all of these things are adhered to. Now,

the problem is that's under the assumption that's that that that that this is your building.

You design your building for for a specific scenario. If you do something

specific scenario. If you do something on the outside or if you change that design, that also needs to be approved.

I am not personally familiar with what the regulation is about. um maintenance

or like uh the works that require scaffolding on or what kind of approvals would be needed. Um uh so I'm not sure about those in particular. But when it

comes to the building, we try to make sure that the building under any reasonable fire scenario or any fire scenario that that could take place that the building will stay standing. The

people will escape. They would be or rather they would be afforded the best chance to escape and make it out safely.

>> Thank you Dr. Arabi for sharing your insights with us. We were speaking to Dr. Anoir Arabi. He's lecturer in fire safety engineering at the University of Queensland.