Very cheap, very easy to produce and a very effective tool.

So Jason's going to set it up in a minute.

He's got his fuel in there.

So you can see he's got his fuel in the corner there.

And I think he's got some little pellets in there to help keep the fire going.

What we'll do is we'll light the fire up and we'll guide you through the stages of development.

So in the early stages you're going to see a fuel controlled fire.

You'll see air flowing in towards the base of the fire, setting up the convection current, the heated smoke.

And air will start, will move up the top of the container and will flow out through the top.

It'll move across the ceiling and flow out through the top there.

So what you want to see is a typical bi-directional laminar air track or flow path.

As the fire starts to develop the thickness of the smoke will start to increase.

The neutral plane will come down and eventually we'll get to the stage of the competition between the fire's need for air and the amount that's being blocked off by the smoke.

So as the pressure plane increases it starts to block off the inlet.

And eventually we'll get to the stage where the fire needs more air than that opening will allow.

And you'll start to see the neutral plane will go turbulent, moving into a ventilation control profile there.

You'll see all that.

You'll start to see, you won't see a typical flashover but you'll start to see flames coming down from the ceiling area.

That's getting pretty close to flashover.

There'll be a rollover.

And sometimes we'll put a little prop in here and you can see it actually starting to pyrolyse.

So once we do that we'll start playing around with the air.

So we'll build it up to a certain stage.

We'll exclude the air and the fire will go out.

We'll have to re-ignite the fire.

And then as the fire gets hotter and hotter, as we close it off, it's going to re-ignite.

And we'll get to, eventually, we've got to get the temperature right.

There's a bit of a skill between the durability of the box and how long it lasts and getting those backdraft conditions.

Once you get that temperature you can just do backdraft after backdraft after backdraft after backdraft.

We got up to about 50 or 60.

We used to have competitions so you'd get the most backdrafts.

But if the box burns through before that, you start to get leakage.

You won't even get one.

We'll also, what Nick Jason started up.

The other thing that, with this fuel it's a little bit damp.

So it's going to be interesting to see how much steam we get out of it right away.

Generally when you're doing these it's really important not to get in the smoke.

Tell your students to stay out of the smoke.

We're really lucky here.

We've got the ability to sort of put the smoke out.

We're not being affected by the wind.

If you haven't got the luxury of this sort of facility, you have to think very carefully about where you do this demonstration.

Because you do not want smoke blowing down into the student spaces.

It's not good stuff.

And if you have to, put a breathing apparatus on.

If we were outside now, I'd get the lead instructor to put a breathing apparatus on.

Another thing I want to show you, to reach a certain point.

When it gets hot enough, we'll put a mat or something over the top here to see if we ignite the smoke.

In the early stages it won't ignite.

Nothing will happen.

And as the fire starts to develop, as you start to get more fuel, you'll be able to ignite that flame.

You take it away, it'll go out.

And eventually, it'll be hot enough, so as soon as you actually see it, if you stick that opening enough, the fire will actually go out inside.

And we'll have smoke discharging and auto-igniting outside.

That's a really cool phenomenon to show you guys.

We've got our fire lit in the corner.

You can already see we're starting to develop a neutral flame.

In the early stages of a fire, the first thing to come off is water at about 100 degrees Celsius.

And what happens coming off now will actually be water vapour.

We've got a little bit of wind coming through here.

So in the early stages, white smoke, that's probably a bit of steam coming off there.

The smoke will start to pyrolyse.

We'll start to get some yellow or even brown smoke coming off.

That's the lignin and the tar breaking down in the timber.

When we start to get the black of smoke, we know we've got flaming combustion, active flaming combustion involving the linings itself.

So really, we've got a very small fuel load.

What's going to be burning is the contents, the actual linings themselves, the actual structure itself.

You can see the level of neutral flame.

It's just around about there.

It's nice and lazy.

It's a nice laminate or smooth neutral flame.

Yep, starting to get a little bit of change of smoke colour.

The volume of smoke is increasing.

If you've got a good view of the front there, you'll see the white smoke will sit at the bottom of the neutral flame.

That's the pyrolysis products.

It's sitting down low because it's denser.

It's actually quite heavy.

It's a lower temperature.

The flame's starting to roll the ceiling there in the box.

Just starting, so it's not actually a rollover yet, but the flame's bending.

That's pretty common when you've got a fire located in the corner of the room.

If you put the same fuel load in the middle of the room, that flame won't link because it's got air coming in from 360 degrees.

Developing nicely.

Starting to get a little bit of change of smoke colour.

See that nice smoke just sitting at the bottom there?

You'll see that in the container too in the demos today.

You'll see that white colour of smoke.

If you get the lighting right, you'll see it coming out of the back of the board, just sitting there.

When that ignites, it's almost a transparent flame.

It actually goes down seeking the oxygen.

Quite distinctive from the flames you'll see running the ceiling.

Take a look at the volume now.

Rapidly increasing.

We're starting to get some darker coloured smoke there.

The flame almost right across the ceiling level.

Now we're starting to restrict the oxygen supply.

It's still in the fuel controlled mode.

Fairly laminar neutral flame.

What I normally do is I'll just let this build pretty close to the point where it goes into ventilation control.

Did you show that transition from fuel control to ventilation control?

Look at the change in condition.

Just by turning that switch on, you can see that it's going from fuel control to ventilation control.

You can see that it's going from fuel control to ventilation control.

Look at the change in condition.

Just by restricting that air supply a little bit, there's a massive change in condition.

Neutral flames are in about here, much darker.

It's just becoming turbulent.

Of course, we've restricted the size of the opening.

Of course, we've restricted the size of the opening.

We're starting to get a competition.

The fire's still not real big, so it's able to draw enough air in reasonably well.

If you lowered that occlusion a little bit more, would you start to get some pulsing?

Yeah.

Just let it go to ventilation control.

It's not quite flashover, but in this scale it's about as close as we're going to get to flashover.

Just about put the fire out there by restricting the oxygen supply.

I think we can go full back.

It's good to have a bit of paper or something to actually start playing with the smoke now.

What we normally start doing now is see if we can ignite that smoke.

The answer should be no.

Okay, there you go. Look at that.

Perfect.

So what's happening there?

Wow.

There's a smoke burn.

That's fairly clean-looking smoke.

Very early stages we've already got enough flammable fuel causing the mat to ignite it.

If we go back, let the mat control the gas.

This will do it.

This will force it.

It'll go off.

Changing cover of the smoke.

Volume of smoke's changed.

So it's disconnected right now.

Or it was for a second.

Did you see that?

Yeah, yeah.

What I like to do sometimes is cut it off that way because I can actually start to see that pulsing.

I make it, you know, I can see it pulsing.

I can see it pulsing.

Cut it off that way because I can actually start to see that pulsing.

I make it, you know, much more ventilation controlled.

What I'm trying to do now is get a separation.

There we go.

Oh, yeah.

So, you see that?

Yeah.

So, you see inside there was practically no flaming combustion.

But it was hot.

Above the auto-ignition temperature.

Just needed to get outside.

See, that's just on the edge.

Right on the edge.

Now, some of these techniques we'll show you involve putting water above the doorway.

Cooling that down.

So, when the smoke comes out, superheated, instead of meeting a preheated surface, it meets a cold, moistened surface.

Reduces the chance of the ignition occurring.

So, Jason's actually cooling above the box there.

He's trying.

No pressure, no pressure.

Look at that.

The separation there.

That's auto-ignition.

Look at it.

We've put it out.

So, you can really show the relationship between air and fire.

We'll have to crank it, mate.

So, at this point in time, the box is not hot enough to backdraft, so it's going out.

So, the challenge now, when you're doing a demo, is to get the temperature of the box up without burning the outside or without getting it breaking through there.

Because once you do that, you can't demonstrate the backdraft.

So, it's a bit of a balancing act now.

What we also try to do to preserve the box.

Just a little bit of water above that area there.

That extends the life of the box.

Look at that.

Didn't quite do it.

Sometimes you can push it back and get it to backdraft.

Look at that.

Let's get the temperature pulled up a little bit.

So, basically, you know the big trucks you've got outside, you don't need them.

You'll be used to one of these.

The person will show you what all your problems are.

You can do a lot just with that.

Here we go, the backdraft.

Now, that's really coming out pretty fancy.

Look at the pressure.

It's right on the edge there.

So, we've got the temperature there.

Just got to keep the integrity of the box together and we can start demonstrating some backdrafts.

Let's get the temperature up.

It's a temperature-driven event.

For auto-ignitioners anyway.

It's not quite hot enough to auto-ignite.

It's not hot enough to auto-ignite.

Pull it up a little bit more.

You might have a better, better look.

Going back to a white smoke, indicating pyrolysis.

Pyrolysis, relatively low temperature.

Middle is 300 degrees Celsius.

Flaming combustion, 600 degrees Celsius or more.

Just one thing, guys.

We've never not backdrafted one of these things.

No pressure show.

Actually, sometimes it's good to actually not put water above there, because it becomes an ignition point for you.

Pull it up a little bit.

There's a number of ways you can trigger a backdraft.

One of them is through auto-ignition.

One of them is from the original fire rekindling.

And we're trying to use the auto-ignition method here.

And what we've actually been doing,

Jason's been lighting it up when we haven't got the auto-ignition.

He's been helping it.

And that could be, the mechanism could be steering up of an ember from the air-trap into the building.