Original subtitles

We've all experienced fire in some form.

Its discovery transformed human existence.

Overnight, cold damp caves became warm cozy havens.

One of the most terrifying places

to experience a fire is in your own home.

In this episode, I wanna see what

really happens in a house fire

by setting a house on fire.

I'm going to find out exactly what it takes to start a fire

and experience firsthand what it's like

to be inside a burning house.

(dramatic music)

(window breaking)

I've always been fascinated with how the world works

and I've got lots of questions about why things happen.

To find out the answers, I'm gonna blow stuff up.

For fire to exist, we need three essential elements

often called the fire pyramid.

That's fuel, oxygen, and heat.

So, fuel is anything that burns.

Oxygen, that we generally have in abundance.

And heat, we sometimes have to provide ourselves.

(dramatic music)

(flamethrower firing)

Yes, a flamethrower is a lot of fun,

but the point is, if you remove any one of these elements,

heat, fuel, and oxygen, there won't be a fire.

(dramatic music)

(flamethrower firing)

All matter, in one sense, has heat

because matter's made of molecules

and heat's produced when molecules move.

But, it's only when molecules are moving really fast,

and there's sort of energy being released,

that it feels hot like it does there.

What would all of that mean

if I wanted to set fire to a house?

For scientific purposes, of course.

Well, we've got oxygen in abundance

from this clean, fresh country air.

We've got heat from this rather

large box of oversized matches for extra safety.

And, I give you,

Fuel.

This is your typical, three-bedroom New Zealand home.

Perfect for our purposes

because most of us live in one of these

and I'm going to set it on fire.

So here's the plan.

Basically, once the house catches fire,

we're gonna stay in it as long as we can,

but when it gets close to the flashover point

which is apparently unsurvivable, we're going to leave.

Now, unfortunately, a camera man, Clayton,

has selfishly refused to lay down his life

for the furtherment of science

so he's gonna leave as well.

But we put security cameras throughout the house

so that we can catch the action after we leave.

We know that smoke rises so, in order to get

the best and longest picture possible,

the cameras have been positioned low to the floor.

In a serious fire, like the one we're going to create,

extreme heat is going to be an issue

and presumably our cameras, being plastic, will melt.

It'll be interesting to see

just how long they keep broadcasting for.

To beat the heat, I've come up with a plan

that can only be described as cunning.

(liquid pouring)

Now, everybody else has great faith in the security cameras,

but I'm a bit concerned that when this room

reaches flashover temperatures,

which is about 600 degrees Celsius, it will all melt.

So, I've come up with, what I think, is a genius plan.

Basically, I've put this GoPro inside a fish tank

and filled it with cold water.

My theory being that this will

survive the flashover temperatures

and record some stunning pictures of the room

or, it will melt and boil and none of this will work.

One of those two things.

(door opening)

(door shutting)

This is a replica of the house we're going to burn.

In order to understand more about what's going to happen

in our real house, I'm going to set this one on fire.

Yep, those are our model flamingos.

I'll explain more about them later.

To imitate the real thing, we made a model lounge

with the same kind of furnishing materials

you'd find in an ordinary home.

The first thing I noticed is how quickly the fire spreads.

Smoke quickly rises to the safety glass ceiling

that we built and covers it in dense, black soot.

If this was a real room, and I was inside,

I'd be in big trouble.

And it's only been a matter of seconds.

In no time, fire engulfs the entire house.

(fire burning)

What struck me the most, was when the fire had lots of fuel

and plenty of oxygen, and you let it burn, it runs amuck.

It makes me wonder how fast the fire will spread

in a real house with me inside.

So, why did the fire spread so quickly?

One of the things that you're probably not thinking about,

as you're sitting at home watching this on telly,

is that you are plunked down

in the middle of a giant petrol bomb.

Let me explain.

Your average three-seater couch

made of modern, synthetic materials,

that's the equivalent of four of these cans

of petrol when it burns.

Your two-seater, that's about three of these cans.

If you've got another one-seater in the room,

then this, another two cans.

Curtains, cushions, stuff like that,

toys, your carpet, and your audio visual stuff,

your telly, your CDs, all of that.

That's gonna be at least two more cans of petrol.

So, your average modern lounge, it's cozy, it's convenient,

but it's also roughly the equivalent of 35 liters of petrol.

Nice to sit in but very flammable.

It's not just the flames from your homemade petrol bomb

that you need to worry about.

All those synthetic materials also

produce toxic fumes when they burn.

Smoke is effectively unburnt fuel.

It's small particles of solid, liquid, and gas

that are individually too small to see

but when they combine together, we see them as smoke.

And smoke's a major factor in any house fire.

Now, the Fire Service have a thing they call a smoke box

to demonstrate the behavior of smoke in a fire.

We built our own smoke box which is a replica, kind of,

of the house that we are going to burn down.

Let's see what happens when you set it on fire.

(torch blowing)

If this was a small campfire outside, it's okay

because the heat and the smoke have got somewhere to go.

When you have fire in a room, all the heat and the energy

and all that smoke, all that fuel

is contained within the box.

So, what you're seeing is the smoke layer

is quickly filling up the room.

The heat up here is building up hugely

and our small fire in the corner

is starting to radiate out.

Now, if you look at the smoke,

this kinda dirty, black, green smoke,

what that means is that the temperatures inside the room

are above that combustion level

but there's too much fuel and not enough oxygen.

It's like, you can have a small fire burning in a room

that burns up all the available oxygen

and the whole thing seems to quiet down,

soon as you open a door,

(fire roaring)

you get this thing called rollover

which is the, which is the flame actually

burning along through the smoke.

So, that's why the Fire Service say you should

touch the door with the back of your hand

and if it feels hot, then you shouldn't go in there.

Rollover is a precursor to flashover

which occurs in a fire when the temperature

in an enclosed space is so high,

it ignites all flammable material simultaneously.

(dramatic music)

We let our smoke box burn out and got a glimpse

of just how destructive fire really is.

So, the energy and the speed of a fire

just in a small box was pretty intimidating,

which makes me wonder what's it gonna be like

when we actually burn down a whole house.

Next, I recreate the most typical

of all house fire scenarios,

one that starts in the kitchen.

And I find out what it's really like

to be inside a burning house.

And it's quite getting quite dark,

surprisingly quickly.

(electronic whooshing)

The place where you're most likely to encounter a fire

in your house, is in the kitchen.

Now, when a fire starts, if you think

about your fire pyramid there's some things you can do.

The first thing is to remove the fuel,

hard to do when it's burning oil.

The next most obvious thing is to take away the oxygen.

And the easiest way to do that

is just to put the lid back on

or use a chopping board.

It's a big solid surface, seals it,

no oxygen, no fire.

Normally, water is a really good way to put out a fire

because that takes away the heat

but something happens when you add water to an oil fire

which is quite catastrophic.

(flame surging)

When you add water in its liquid form

to superheated boiling oil,

it almost instantly vaporizes and expands

eighteen hundred times and creates a massive fireball.

(dramatic music)

Well, that's creating heat.

What about measuring heat?

Remember the replica house and the model flamingos?

You thought they were just for show, didn't you?

I'm also really interested in precisely measuring

the amount of energy given out by the house

when it's on fire in the form of radiant heat.

And to do that, I'm going to use pink, plastic flamingos

arranged at precise one-meter intervals

all the way out from the house

and the degree of melting of the flamingomometer

high temperature detection array will tell me

precisely how much energy the fires are missing.

We've all had to back away from a fire

when the heat gets too intense.

Being polypropylene plastic, my flamingos don't feel pain

but have a melting point of around 200 degrees.

I'm curious to find out how far back they'll melt to.

We're eight meters out,

I'll be interested to see what happens.

Enough of models and flamingos and science,

we know the theory, time to get inside a burning house.

Obviously he haven't hasn't many

fatty breakfasts the last we were of this outfit.

Peter Wilding works the New Zealand Fire Service.

He's manager of fire investigation and arson reduction

which is quite helpful

because we're about to set a house on fire.

Most people die in fires but from the,

the product of the fire, the smoke, the cyanide.

The other thing that gets released inside the building

and this will keep you free of that.

Peter had plenty to say about what to expect

and some of it made me a wee bit nervous.

It's going to get to 600 degrees in there.

There'll be fire above us, so keep low.

In fact, the key message at any fire

is to get down, keep low, and get out.

Except in this case, we're going to ignore

what's probably the most important part to get out with.

So I'm about to do something

that my mother tells me not to do.

I'm gonna play with matches.

(dramatic music)

(breathing with oxygen tank)

I'll leave the matches there.

(beeping)

So we've got a very small fire going

just over here in the corner.

And already, it's been about 15 seconds,

it's starting to heat up.

This is a typical house fire scenario.

Someone discards a cigarette at the back of the sofa.

The fire is alight in seconds,

if it's nighttime and the occupants are in bed,

and they've got a smoke alarm,

it would already be sounding

and they'd have time to get out.

But, if they don't, they're in big trouble

because what happens next happens really fast.

We're probably gonna

be about three or four minutes.

And an average house nowadays

with foam sofas like we've got here,

before this room is totally engulfed in fire.

And it's starting to spread through the house.

But as you can see, if they had a smoke alarm,

the family would know about it

and they would already be evacuating now.

In time, this fire will heat that smoke

and the smoke itself will ignite.

And within a short period of time,

this entire room will be engulfed in fire.

We'll just crouch down

and get underneath the smoke level now.

And it's quite getting,

quite dark surprisingly quickly.

Certainly if you stand up,

you'd be struggling to see doors

whereas if you stay down low,

you can see where the door is and you can safely get out.

Most people die in house fires from breathing the smoke.

They go through such nasty, nasty toxins in it.

You can certainly start

to feel the heat from it now.

You can see how the fuel's

starting to rollover size.

Yeah, yeah.

Very shortly, that will ignite

and other fuels in this room are gonna do it.

And then we're gonna exit here.

(breathing with oxygen tank)

Stand, get all those out here still.

(fire crackling)

(crashing)

Remember the smoke box and flashover?

The point where everything in the room ignites?

We're almost there.

Peter and I scurried manfully out of the house.

I would suggest we go right around

and without taking your gear off.

At the moment, that room's not survivable.

Nobody in that room that's still in there now

would be surviving within a minute.

Yeah.

Very shortly, everything in that room

will be ignited

and that's the point we call flashover

where everything ignites.

Suddenly a window breaks

(glass shattering)

allowing a fresh flow of oxygen into the room.

Remember, when I opened the door to the smoke box

and added oxygen, the smoke ignited.

Here, when the window breaks, effectively,

the same thing is occurring.

Oxygen rushes in and in no time

everything in the room ignites.

This is flashover.

At about this stage would be kinda

treading up into the roof space as well

in through the whole way start to go

into the rest of the house.

It's been three minutes since I lit the couch

and already temperatures exceed 800 degrees.

What is interesting though

is that if you were in another room in the house,

you still've got a chance to get out

if you knew about this fire.

If this was downstairs, you were upstairs asleep,

you wouldn't necessarily know this was going on.

Sometimes people report glass breaking

and they think there's a burglary or something.

But you can see what you got downstairs.

(water spraying)

The firefighters damp down the room

to allow us to inspect the damage.

Unlike with our fat fire,

water is an effective way of fighting a house fire

because it separates fuel from oxygen

and lowers the temperature of the room.

In less than four minutes, the lounge

was reduced to charcoal.

Any valuables in there, books, CDs, computers

would be history.

It's just toast.

But how would a goldfish have fared in there?

I'll find out when I attempt to retrieve

the GoPro camera I put in the fish tank.

Later, we unleash the full force of nature,

and let the house burn,

and we sacrifice our flamingos for science.

(electronic whooshing)

(match striking)

To find out what it's like in a house fire,

I'm setting an actual house on fire.

(fire crackling)

And with the help of the Fire Service,

a few security cameras, and a GoPro camera, and a fish tank,

(crashing)

I was able to get as close to flashover

as I would ever want to be.

With the fire under control,

it's time to go back into the room,

assess the damage, and rescue the GoPro.

Man, there's just nothing left.

Yeah, there's nothing salvageable.

How long after left would this have happened,

a couple of minutes? Three minutes maybe?

Yeah, I'd say, yeah.

So three minutes after we were gone,

it turned to this.

So our room is toast, what about my personal experiment,

the camera in the fish tank?

(laughs) Wow, it kinda survived.

If you had a goldfish in there,

he'd be looking rather sad.

(Nigel laughs)

Well, I mean, just look, you've got about,

inside she looks all right, I'm very hopeful.

I'm very hopeful that our experiment

will produce some usable pictures.

Our GoPro footage tells a dramatic story.

The window smashes, (glass breaking)

oxygen floods the lounge.

Now, the heat in the lounge builds at a quicker rate

than the room can ventilate.

The indications of a potential flashover,

thick and dark smoke, begin to appear.

Next, rollover occurs in the ceiling.

This is the ignition of the gasses

that have collected high up in the ceiling

and it's considered the last sign of impending flashover.

Time to get out.

Now, the heat is forced back down onto the room.

Temperatures arising so rapidly

that even though not everything in the room

has the same ignition temperature,

it all appears to ignite simultaneously

which means flashover has occurred.

See, the flames are actually licking the carpet

right up to the levees.

Once the flame is at the floor level,

we've actually got reasonably even temperatures

from the floor to ceiling.

So, anywhere between 600 and 1,000 degrees in that room.

If you try to breathe, that very super heated air

would just scorch your respiratory tract

and you wouldn't be able to breathe.

The fumes that are coming off it,

polyurethane foam, we've got hydrogen cyanide,

hydrogen chloride gas, carbon monoxide

being given out in voluminous quantities.

You just wouldn't have a chance of surviving this.

While Peter and I check out the GoPro footage,

the house burn continued on.

Just as we saw in the replica house,

the fire spread up into the roof,

traveling through the roof cavity

and into the rest of the house.

(fire crackling)

Our security cameras proved a worthwhile investment

providing us with some of our most compelling footage

putting us right inside a burning room.

It must be between 600 and 1,000 degrees in there now

and our security cameras are still bravely broadcasting

even as we can see here (sustained beep)

the lens is melting.

But everything has a breaking,

or in this case,

a melting point and presumably (intermittent static)

that's what happened here.

The camera simply melted. (sustained beep)

In a house fire, heat causes molecules

to move at high speed around a room.

In doing so, they create an increase in pressure,

pushing at the walls, ceiling, floor, and windows.

Because the windows are the weakest part of the house,

they break and bust.

This is what we in the trade call

a fully engulfed house fire.

And as we can see, the flamingomometer heat detection array

is bravely doing its job.

They're almost gone apart from one.

The heat, even at about 20 meters,

is incredibly intense.

Radiation is the heat we feel coming off a fire.

It warms the air using heatwaves that radiate out

in all directions until its absorbed by an object.

In this case, my flamingos.

The heat given off overwhelmed my flamingomometer.

Every bird suffered at least partial melting.

That means, even as far as eight meters out,

temperatures touched at least 200 degrees Celsisus,

hot enough to roast the chalk.

In no time at all, the flames had engulfed the house.

Nothing I'd seen so far had prepared me

for the magnitude of an actual house fire.

The speed at which a wooden structure

is transformed into a blazing inferno was startling.

The feeling of being at the mercy of nature

was simply overwhelming.

The science of fire is pretty straight forward.

A chemical chain reaction that needs heat, fuel, and oxygen.

But fire is also undeniably ferocious.

It's not a living thing but it feels like it is.

It might be just a chemical reaction, but it's a fast one

and it's insatiably hungry.

So I, for one, am going to treat it

with a lot more respect from now on.

What we've seen is that all

of the scientific principles of fire

that we demonstrated on our very small house model.

It's exactly the same when you

play it out on a really large scale.

And I think the big lesson is,

the big thing that the science of fire teaches us

is that the fire will always win.

So get out.

(dramatic uplifting music)