# Forum More Stuff Debate & Technical Discussion  Bloody Range Hood Pipes

## rrobor

You cant have a fire in a range hood pipe, the fire couldnt get through the filters. either you heard wrong or theres a villiage somewhere missing their idiot because hes writing regulations

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## Vernonv

> You cant have a fire in a range hood pipe, the fire couldnt get through the filters.

   Unless the filters catch fire. :Rolleyes:  
The villagers want you to come home? :Biggrin:

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## rrobor

Yes it seems someone has issues with their Physics so perhaps its your villiage. If the filters catch fire they will gain oxygen by dragging air down the flue and due to that and the other issue that a fire gains heat by extracting it from other places so causing the back of the filters to be very cold. Only after the whole place is involved will the pipe catch fire.  So please think before you plod your size 10 in it, shooting fish in a barrel is poor sport.

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## chipps

Got me stumped..... 
Thought plastic would melt  :Shock:  
Scenario: Turn on stove or oven but not rangehood, surley it's gunna do damage to plastic flue.

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## chipps

Disregard my above brain-fart....... 
Just poured boiling water down sink & the penny dropped  :Rolleyes:

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## rrobor

We are talking about a flue behind metal gauze in a range hood, to melt that you would have to have the temperature of the filters hotter than you could touch, as thats about 70cm from the stove top if you can achieve that then you will have more issues, and a melted pipe will be a minor problem compared to the other damage. Sorry pushed button before I saw your second post

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## chipps

> Sorry pushed button before I saw your second post

  Ta for the explanation & yep I type before thinking  :Biggrin:

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## Vernonv

What a load of rubbish.  

> Yes it seems someone has issues with their Physics so perhaps its your villiage. If the filters catch fire they will gain oxygen by dragging air down the flue...

  It will probably get more air from the kitchen then it will from down the flue.  

> ...and due to that and the other issue that a fire gains heat by extracting it from other places so causing the back of the filters to be very cold.

  How do you dream this crap up? I think you should test your theory for us. :Doh:  
You can sprout as much BS as you like, but the bottom line is that you can't unequivocally say that the filter will stop a fire entering the flue.

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## rrobor

Please dont do this, you are disregarding a few thousand years of the progress of mans understanding of how things work. Its not my ideas, look up the Davy lamp invented in the early 1800s I believe, there you find point 1 as to where you err. I could do the other points if there was a point but that seems pointless.look I even found you the site

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## Vernonv

Rob, you rattle off these "facts", but they rarely address the point and they rarely seem to have a point in their own right ... actually they seem more like an attempt the dodge a previously sprouted unproven/false "fact" and generally also contain some puerile attempt to belittle those who don't share your views. 
Now back to the point : 
You say "you can't have a fire in a range hood pipe" and that is not correct. Given the right circumstances, it is entirely possible. It's weird how many manufacturers specify metal flue ducting and/or fire retardant ducting be used with their range hoods ... but then again they don't have your wealth of knowledge in this area.

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## murray44

I find it entirely possible that a rangehhod flue could catch fire, not likely, but possible. The inside of them would coated in nice greasy flammable material. All you need is for the fan to go up in flames and the flue will follow. 
It's not going to drag oxygen down the flue from the top, it's going to draw air from the kitchen through the possibly flaming fan. That sounds like Chimney Physics 101.

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## rrobor

You are now all bending things to suit an arguement. If we are talking about a range hood it has a metal grille to catch fats the fan is above that and all fan motors are sealed. If we are talking as to some form of chimney with a fan then all bets are off, but only an idiot would fit that in a kitchen. Once the whole surface of the hood is alight, the only place the fire can get oxygen is down the chimney so please gentlemen read as to the Davy lamp and the temperatures created, because I dont believe I have to argue its principles in the 21 st centuary which were proven and has been used since 1806

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## murray44

Well I must have misinterpreted the original post which was inquiring about a flue for a rangehood. 
I didn't realise he wanted to put a miners lamp in his roof.

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## Vernonv

> You are now all bending things to suit an arguement. If we are talking about a range hood it has a metal grille to catch fats the fan is above that and all fan motors are sealed.

  That's what we are talking about ... what are you talking about?   

> If we are talking as to some form of chimney with a fan then all bets are off, but only an idiot would fit that in a kitchen.

  It's quite a common thing to see in old houses that used to have a wood burning stove and now have a conventional stove in it's place (under the chimney with a fan in the chimney) ... but yeah, they must be idiots if they didn't consult you first on the best way to install it. :Roll Eyes (Sarcastic):    

> Once the whole surface of the hood is alight, the only place the fire can get oxygen is down the chimney

  So where did all the oxygen in the kitchen go? I don't know about you, but I don't live in a vacuum?

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## rrobor

Again you twist a fan in a chimney designed for a fireplace  is not the issue The guy asked as to a rangehood and piping please dont try to create issues as to how you can use a firplace, where do you need a pipe for that. As to not understanding the connection to the Davy lamp, Im not going into that as there is no point arguing with one who cant understand.

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## Vernonv

> Again you twist a fan in a chimney designed for a fireplace is not the issue The guy asked as to a rangehood and piping

  You're the one that introduced the whole chimney/fan idea.  :Doh:  For my own part, I was simply stating that the use of a chimney and a fan is a simple, non-idiotic solution for a particular situation.   

> please dont try to create issues as to how you can use a firplace, where do you need a pipe for that.

  Yes let's compare all this to a mining lamp instead ... that will surely clarify things. :Roll Eyes (Sarcastic):   
C'mon keep up Rob.

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## BRADFORD

Don't stop now guys I'm luvin this 
Bradford

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## rrobor

Sorry bradford I cant answer their questions as to the miners lamp, If people cant understand the principles involved then it comes down to insults, and do we all really want to start that. So no, Noel called a halt and Noel is correct. The options to this aguement are limited, and to force people with limited options into a corner is going to create resentment. As such I bow to the master, I am but grasshopper.

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## watson

No halt called at all.............its just moved in here so that the OP can see the advice he received. 
Seconds out..........go for it.

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## rrobor

Sorry Noel, I didnt intend to imply you shut it down. I just tried to hint perhaps it was best shut down as I could see people getting hurt and that was not my intent. Rob.

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## Vernonv

> Sorry bradford I cant answer their questions as to the miners lamp, If people cant understand the principles involved then it comes down to insults, and do we all really want to start that.

  Rob we are talking about whether or not a fire can start in a rangehood flue. You made a rash comment and then try and prove it using (of all things) a miners lamp. So rather than throwing up obscure references and insults to try an divert the discussion, you should instead address the original point.   

> The options to this aguement are limited, and to force people with limited options into a corner is going to create resentment.

  I'm sorry that you feel you have been forced into a corner by rational discussion, but rather than feel resentment, you should instead look on the positive side - by being wrong, maybe you actually learnt something. :2thumbsup:

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## murray44

Thanks for the concern, I did get hurt........fell off my chair laughing......hahaha

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## rrobor

Ah well I tried.Scientific fact 1/ In 1806 Davey proved that a flame could not pass through a grill and the grill would stay cool. This is the reason theres a grill in a rangehood and no area is allowed to be uncovered. When the whole area of the filter side is covered by flame, no air can get to the seat of the fire other than by going through the flame, which can not happen, or by entering by being sucked down the chimney, which can. Any reasonable person must understand that the air will be sucked down the chimney. Scientific fact 2/  E=MC squared. For every action there is an equal and opposite reaction, and other such facts tell us that that we can not gain or loose energy we can only transform it from one state to another. So where does the fire gain heat. It does so through the air it draws, Who has not set their hand alight with some fluid or other and was surprised at how cold their hand was as the flame burned. This is due to the need the fire has to gain heat, it draws it from your hand. So the back of these filters will be near freezing point as will the flue.
  That is simple science gentlemen, Isaac Newton, 1642    Humphrey Davy 1816 and Einstein 1900+ all gave as the simple facts as to why that is so, not me. So trying to make fun of me with rubbery logic that dont work and talking about a lamp in the ceiling does not reflect badly on me, I sincerely suggust you consider dropping this before you dig your hole deeper.

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## chipps

That is simple science gentlemen, Isaac Newton, 1642 Humphrey Davy 1816 and Einstein 1900+ *& Chipps 2009*   Stuff this, I'm gunna test it out on the stove meself !!!!!!!  
Now lets see,   1litre pot of petrol (boiled)1litre plastic bag of petrol suspended above filter.Vacuum cleaner sucking from plastic flue.Fat from last nights grilled lamb chops (smeared onto filter)Looooong match (I'll tape it to a fishing rod to be safe)
I'll be back soon

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## murray44

Rrobor, you're a legend,
You've jumped from Einstein's theory of relativity straight to Newton's 3rd law of motion. Nice work. Didn't Galileo have something to do with rangehood fans?
Davey's miners lamp is icing on the cake. 
And the Nobel prize for (insert category here), goes to......Rrobor. 
p.s. I've never been stupid enough to set my hand alight.

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## rrobor

Bad science chips, heat from flames  could heat up the edges of the hood travel up the sides  and the gas off the petrol (petrol doesnt burn only petrol vapour does) in the canopy could reach flash point near the bottom edge and you built a bomb

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## murray44

I missed an obvious thing there. He obviously cooks his steak and chips in petrol. mmmm.........I should have realised that.

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## Vernonv

> Ah well I tried .... blah ..... blah .... blah .... blah ....  reflect badly on me,

   Sorry, but all that hot air does not prove that the flue can not light up given the right circumstances.    

> I sincerely suggust you consider dropping this before you dig your hole deeper.

   If I'm digging a hole, it is only to get to your level .... but I'm thinking of giving up, as I don't have the energy or desire to dig a hole that deep. 
PS - I also have never set myself on fire. But please, you keep playing with those matches, you hear.

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## rrobor

Murray 44 and Vernov. you miss each and every obvious point, why stop now. You keep trying to make a fool out of me by making rediculous points. Please stop, I dont want to go any further with this as stated because nonsence science is being used. Chips had fun and great stuff, thats fine, but you are trying something else and its only you opening yourself up to ridicule.

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## Vernonv

> Murray 44 and Vernov. you miss each and every obvious point, why stop now.

  Well I'm sure I wouldn't miss a point relevant to the topic ... now you just need to make one.   

> You keep trying to make a fool out of me by making rediculous points.

  You're the one making a fool out of yourself. Maybe your points should address the topic, instead of trying to twist the topic to align with some scientific trivia.   

> I dont want to go any further with this ...

   Fine ... stop then.   

> ... as stated because nonsence science is being used. Chips had fun and great stuff, thats fine, but you are trying something else and its only you opening yourself up to ridicule.

  You should re-read the posts and then you may truly see who is opening themselves up to ridicule ... but somehow I doubt you will be able to see past your own ....

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## watson

This morning I Googled Range Hood Fires.........Range hoods.....Range Hood Pipes.
I shouldn't have bothered.
Google points straight back to this thread  :Doh:  
How embarassing

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## rrobor

Ok Vernov Ill make a few  Point 1 the chamber above a rangehood is a sealed unit with a flue and a fan. The fan is a sealed unit so there is no chance of that catching fire, It may have a lamp, that is made for a hood and has to pass certain specs, so its remote that thats going on fire so where is the fire coming from. Point 2 The Davy lamp, Davy proved that if you put a grill up gas could travel through that but flame could not so there is no method of getting flame to pass through a grill. Einstein and Newton proved that energy is never lost only transformed. Flame is pure energy it is a material transforming from one state to another. With Chips if he didnt explode, its his Sunday roast fat turning into ash. To do that it requires to be able to rob energy from somewhere, that is done by two methods. It transforms oxygen to co2 so it needs air and 2/ it uses heat and like the principles in fridges it draws heat from the chamber above so that will become colder. It is only after the whole area is involved will the flue catch fire and more than likely it will be the top of the flue first or the intensity of the flame below melted the plastic clps holding the grills in and they fell out and then yes then its a chimney. This is first year school science so please stopTrying to disprove it, You wont.

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## rrobor

Hey Noel Should I do a Wiki thingy. Ah no second thoughts perhaps not

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## Bleedin Thumb

> Ok Vernov Ill make a few  Point 1 the chamber above a rangehood is a sealed unit with a flue and a fan.  Sorry its not sealed 
> The fan is a sealed unit so there is no chance of that catching fire, sorry its not sealed either.
>  It may have a lamp, that is made for a hood and has to pass certain specs, so its remote that thats going on fire so where is the fire coming from. Point 2 The Davy lamp, Davy proved that if you put a grill up gas could travel through that but flame could not so there is no method of getting flame to pass through a grill. Einstein and Newton proved that energy is never lost only transformed. The grill is made from thin aluminium with a polypropylene filter fabric matrix sandwiched inside that, if saturated with fat and exposed to a fire would soon burn out.
> Flame is pure energy it is a material transforming from one state to another. With Chips if he didnt explode, its his Sunday roast fat turning into ash. To do that it requires to be able to rob energy from somewhere, that is done by two methods. It transforms oxygen to co2 so it needs air and 2/ it uses heat and like the principles in fridges it draws heat from the chamber above so that will become colder. Thats just over simplistic rot  why would it draw air form above when the it has warm air being drawn into the flame from below? It is only after the whole area is involved will the flue catch fire and more than likely it will be the top of the flue first or the intensity of the flame below melted the plastic clps holding the grills in and they fell out and then yes then its a chimney. This is first year school science so please stopTrying to disprove it, You wont. Well if you don't want to debate something don't bother to offer your misguided opinions.

  Keep up the voodoo science rrober, great stuff. :2thumbsup:

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## Vernonv

Well I think BT put it pretty succinctly. 
Rob, if you want to use science to prove something, then please find the science that fits the application we are talking about. 
BTW, I find it quite amusing that it has taken you 3 pages to admit that the flue can actually catch fire   

> It is only after the whole area is involved will the flue catch fire

  ... so at long last, thankyou.

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## murray44

At first I thought he was pulling our leg, then I thought, no he's serious, then i thought maybe the first scotch of the day was earlier than most.
It's not fun anymore.

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## rrobor

Im done with trying to teach elementary science. To bleeding thumb yes I tried to oversimplify you are correct but you are incorrect in as much as when the entire thing is going to that extent the question as to the flue is moot. So my final post  is my wee poem
  When it comes to the day when you curl up your toes
dont look for me at your final repose
A bad choice again is the choice of this gate
like me quietly ponder burning fat in a grate. 
If you ask me again I might just let you through
So stop this nonsence about a burning flue
Theres more to life than the fats from chippys roast
So please, then think and drop this post.

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## Master Splinter

The mechanism of the Davy lamp - the flame arrestor screen - is not a generic, one size fits all solution.  The screen mesh has to be selected according to the temperature and composition of the expected flame front, otherwise the depth of the mesh can be too small to effectively stop flame propagation. 
There have been cases where even correctly sized but badly maintained flame arrestors have failed: http://www.csb.gov/completed_investi...inalReport.pdf 
With a typical filter, I would expect the major cause of fire in the ducting to be caused by the fat on the filter (or the filter itself for those plastic filter mediums) catching fire, rather than flame passing through the filter. 
According to the spec sheets for most PVC pipes, the pipes themselves are self-extinguishing - so again it would be the fat residue doing the burning.   
Since most pipes vent directly into the roofspace, I recon the material of the pipe would play very little part in the spread of a fire - by the time it got hot enough to melt or burn, you would already have a raging fat fire filling the roofspace with partially burned combustion byproducts just waiting for flashover. 
And...sealed fans in a domestic range hood?  Don't make me laugh!!!!

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## rrobor

I will reply to that as it is correct science and I did make a mistake by calling the fan a sealed unit, I obviously meant the motor was not open  but sealed in its housing, and harking back to the start it was about did the flue matter and the answer as MS states is no, once the filters are breeched, evacuate.

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## Bleedin Thumb

> I will reply to that as it is correct science and I did make a mistake by calling the fan a sealed unit, I obviously meant the motor was not open  but sealed in its housing,

   
Correct science.....love it.... :Biggrin:  
You really have a problem eating humble pie....The fan motor in range hoods is an open electric motor, the only housing is the motors casing - you can hardly have a motor without one....its hardly sealed - its air cooled you nong!   
I think that not only should you eat your hat, its about time you ate your shorts. :Biggrin:   
What other correct bsciense

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## rrobor

Now did I insult you or call you names, no. When I saw I stated the fan was sealed I admitted that as an error as such, The motor is sealed it is not an open motor with brushes so forgive that error. Now your errors which were triflng and not brought up but lets do so now for fat to burn the seat of the fire needs a supply of air if the whole area is on fire the only place the air can come from because it can not come through flame is through the grill. Go experiment if you dont believe me, it happens to be fact The box of a range hood is or should be sealed in as much as it does not allow flame through. The grill in the range hood will last till the stage that the fire is out of control. Once that grill gives way the house will be well lit. So no sorry no humble pie I erred in one section as did you, how about you having a slice

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## murray44

Hey Bleedin, 
Guess what? Rrobor is right. I put a miner's lamp above my stove and set fire to some cooking oil. 
The whole kitchen went up in flames, the only thing left was the flue!!!

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## elkangorito

My comments in blue.   

> Ah well I tried.Scientific fact 1/ In 1806 Davey proved that a flame could not pass through a grill and the grill would stay cool. What kind of grill exactly? 
> This is the reason theres a grill in a rangehood and no area is allowed to be uncovered. The reason for the "grill" is that it is not a grill...it is a filter. 
> When the whole area of the filter side is covered by flame, no air can get to the seat of the fire other than by going through the flame, which can not happen, or by entering by being sucked down the chimney, which can. Any reasonable person must understand that the air will be sucked down the chimney. The above paragraph is totally absurd, given that chimneys work in the opposite way. 
> Scientific fact 2/  E=MC squared. For every action there is an equal and opposite reaction, and other such facts tell us that that we can not gain or loose energy we can only transform it from one state to another. How does E=MC squared explain, "for every action there is an equal and opposite reaction" ?  I can't be bothered to comment upon the remaining drivel.

   I'll try to correct your below statement. Corrections are in red. BTW, maybe this is why you are misunderstood? Your English is not all that good.  

> Now, did I insult you or call you names? No. When I saw that I had stated that the fan was sealed, I admitted that I was in error as such. The motor is sealed...it is not an open motor with brushes so forgive that error. Now your errors were triflng and not brought up but let's do so now. For fat to burn, the seat of the fire needs a supply of air. If the whole area is on fire, the only place the air can come from (because it can not come through flame) is through the grill. Go & experiment if you dont believe me, it happens to be a fact. The box of a range hood is (or should be) sealed in as much as it does not allow flame through it. The grill in the range hood will last till the stage that the fire is out of control. Once that grill gives way, the house will be well lit. So no humble pie. I erred in one section as did you. How about you having a slice?

   rrober, please don't think that I'm "having a go at you". Seriously, I have trouble deciphering your English. Sometimes, I have to guess at what you are trying to say. 
Back to the topic.
As a former Facilities Manager, I can tell you that it is a mandatory regulation in N.S.W. for all kitchen air extraction systems (which incorporates the duct), to be cleaned annually. There have been numerous fires in Sydney that were created by grease catching fire in the duct. The amount of grease taken out of these ducts is unbelievable.
Also, the aluminium filters MUST be replaced fornightly by an approved company. 
The above paragraph applies only to commercial installations. A domestic installation may not have as much potential to build up grease quickly but nonetheless, the same principal applies. 
Almost all of your "laws" do not apply. If there is a flue & its output is higher than the input, there will be suction "UP" the flue. A suction fan excaberbates this situation.
The "grills" in question, function as filters, not as a "fire stops". Aluminium burns very well & it is extremely difficult to extinguish. 
I feel that you about to eat your second hat. Also, please develop a thicker skin...you are leaving yourself open to even more insults if you can't take the minor flack you have received so far. 
Have a fantabulous day etc. :Biggrin:

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## Vernonv

Rob, you try and baffle people with your confused ramblings and "correct science" BS and when that doesn't work, you resort to poetry. :No:  
Now you have all but admitted (on a couple of occasions) that there can actually be a fire in a flue, but yet you still try and argue your "correct science".  
Maybe you should give up before you become the honorary Renovate Forum village idiot.

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## rrobor

OK lets answer  both at once, first Vernov. I didnt want to answer you because you dont seem to understand concepts so it would result, as I suspected, in a match of trading insults, now as you have traded the first, I shall simply ask you to try and understand that Davy didnt invent the lamp first, he invented a concept that fire would not travel through a grill. Elkangorito I thought your science was better than that, you are the only one to come up with the thought that the only reason for the grill is to act as a filter. If we  take that absurd conclusion and say we remove the grill then have an oil fire on the stove  within seconds flames would be up the chimney and into the roof, Please think Next Everybody has this wierd idea that air can travel through flame io get to the seat of a fire. Now I cant tell you who descovered this is wrong  and invented a grate to sit fire on but I suspect His next invention was the wheel. Please think of what temperatures air would reach trying to pass through flame. The point was in a domestic range hood could he use plastic pipe.
Now the science is that the filters act as a barrier to flame in as much as they will stop it passing. If we take the reality of the thing, it will not be a fire on the filters it will be a fat fire or oil fire on the stove. If you dont stop the fire by the time the filters are breeched you will have a major house fire and the flue material will make little difference. As to air being sucked down the chimney, that again is correct the slight pressure of the flue as per chimney effect is nothing compaired to the suction the fire creates. Want the theory of that, The Rocket , the jet engine, They all display the power generated by heating air. So as long as the filters are not breeched due to fire on the stove the chimney will aid cooling the filters. So please if you want to create wooly science, then blame me, sorry no that dont work. Prove your science if you can, personal attacks however well you try to disguise it , is usually the result of not being able to answer to the theory.

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## Vernonv

> ... try and understand that Davy didnt invent the lamp first ...

   Who cares. It has has little relevance to what we are discussing, but you seem to keep harping on about it ... let go of it and move on.   

> The point was in a domestic range hood could he use plastic pipe.

  No it wasn't (not directly anyway) - what started this discussion was that you said "You cant have a fire in a range hood pipe" and I said that was rubbish. So I repeat (again) - given the right circumstances it is entirely possible to have a fire in the rangehood flue (do you need me to type slower so you can keep up?). 
No withstanding all your harping on about "correct science", you have basically admitted multiple times that you can have a fire in the flue. Here, this is from your last post  

> ... say we remove the grill then have an oil fire on the stove within seconds flames would be up the chimney and into the roof,

  and   

> If you dont stop the fire by the time the filters are breeched you will have a major house fire and the flue material will make little difference.

  Sorry, but I don't need science to see that you are contradicting yourself.

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## rrobor

Im sorry your answer is incorrect and your science is incorrect. It was you who stated that the flu could catch fire. Now to do that you need A the motor catching fire. Its all in a case there are no open parts thats not likely. 2/ the lamp catching fire, thats not likely. So you are left with the third option that the bottom was left open or the bottom is breeched. If that happens it doesnt matter one snuff what the flue was made of. Now if you can argue any fact whatsoever as to that being incorrect please do so, but please stop behaving like a little dog yapping at my heels with no facts to back up your growls.

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## Vernonv

> Im sorry your answer is incorrect and your science is incorrect.

  What? ... I'm not talking science, I'm talking common sense.  

> It was you who stated that the flu could catch fire.

  Yes, but only to correct your inaccurate statement ... so what is your point?   

> Now to do that ... blah ... blah ... blah ... clap trap ... clap trap ... growls.

  You have agreed numerous times with my point (read you own posts if you need to refresh your memory) and have admitted that a flue can actually catch fire. But every time I point that out, you have a hissy fit, go off on a tangent and go over the same ground again and again ... are you a goldfish or do you just like to hear/see yourself pontificate?

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## murray44

> Now to do that you need A the motor catching fire. Its all in a case there are no open parts thats not likely.

  Why is it not likely the fan motor could catch fire? People neglect to clean their filters, the motors get clogged and dirty, it's entirely possible the motors could catch fire.

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## murray44

Rrobor. 
Your arguments are based on generalisations (comparing a rangehood to a Davey lamp), gross assumptions and outlandish claims (air will be drawn DOWN the flue into the kitchen). 
Am sending you a ladder to enable you to get out of that hole you've dug.

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## rrobor

OK Murray look at the sense in that. No one leaves the fan motor on when not cooking, it makes a noise and you get up and switch it off. Now if you block the motor it makes a loud noise and chances are it shorts inside and blows the fuse. And yes if we searched records you may find 1 instance. I had a deaf lady leave a bad transformer in a TV till that went on fire, but that was an open transformer. So scratching into the depth of reality the chances of you winning tats lotto 2 weeks running are about as good. As to Vernov and his flue catching fire as stated the flue will catch fire when the whole house is ablase, I have never altered from that, so if that satisfies his need great stuff. As to your other post its trying to insult, there is no science innvolved in it, but that from you has to be expected

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## Vernonv

> No one leaves the fan motor on when not cooking, it makes a noise and you get up and switch it off.

  And your point is?    

> Now if you block the motor it makes a loud noise and chances are it shorts inside and blows the fuse.

  I've had a few motors blow and they generally spark/burn/smoke and DON'T take out the fuse. It's certainly a possibility that a motor could burn out and start a fire. It is also possible that a stove fire could breech the filters. It's also possible that the filters weren't refitted properly after a clean and are not seated correctly (hence leaving a gap). 
I can see many possibilities. You unfortunately have dug yourself into a rather deep hole and are too pig headed to admit that for all the "science" you espouse, reality reigns and flue fires can and do happen.   

> As to your other post its trying to insult, there is no science innvolved in it, but that from you has to be expected

   :Kissyou:

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## rrobor

Just look at your reply. point 1 is that someone switches the fan on there is someone there . A person hears this thing howling what other way can I say this. point 2 all wires etc are within a case of the motor it would be on for some considerable time before the case could get to the heat to cause a flash. The rest of your post is reiteration of  all the rest. If dopey Daisy dont fit the grill yes the flue is a danger If she dont switch off a howling motor. If she sticks a match up to see if it will catch fire. Or if she leaves a fire on the stove till the filters are breeched. The question is not can the flue burn but what needs to happen for it to burn. Im not trying to tell anybody that after the house burns down, suspended in mid air is a flue

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## Vernonv

> Just look at your reply. point 1 is that someone switches the fan on there is someone there . A person hears this thing howling what other way can I say this.

  You are assuming that it will start howling before it goes - I've seen two motors actually get quieter (they slowed down) before they went. Even if it did make a noise, maybe nobody is in the kitchen to hear it - my wife, who does most (all :Blush7: ) of the cooking in our place, is quite often not in the kitchen when she has things on the stove.   

> point 2 all wires etc are within a case of the motor it would be on for some considerable time before the case could get to the heat to cause a flash.

   Incorrect. Most blower/fan type motors are open and are cooled by the very air they are moving. Sparks from the open motor could quite easily ignite a grease/fat covered motor housing and the associated ducting.   

> The rest of your post is reiteration of all the rest. If dopey Daisy dont fit the grill yes the flue is a danger If she dont switch off a howling motor. If she sticks a match up to see if it will catch fire. Or if she leaves a fire on the stove till the filters are breeched.

  So again, you are saying that it is certainly possible for the duct to light up. Why do you keep arguing when you agree with the general consensus?

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## rrobor

Please think before you post again. If the motor was an open brush type motor let us say your wife could smell gas, what does she do, she turns the range hood fan on to clear it.  Now there could be a pocket of gas is in the range hood so the spark of the motor brush would ignight that and the hood the flue and your wife would take a trip very quickly. If you have built such a unit I advise you to get rid of it.

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## plum duffer

As a bloke who regularly reads this forum for some heads up action and also faced with a range hood install this week I am utterly confused... First I thought I would contact the manufacturer and ask if they could remove the 2 spot/down lights at the back of the unit and replace them with davy lamps.. then for the flue well clearly asbestos pipe of some kind can be the only way.. then all the talk of science and explosions has got me buggered - the safest install for a rangehood is at the bottom of a pit covered in a sarcophagus of concrete. No danger of flames down there.. unless some kind of science proves otherwise. Cheers Plum

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## Vernonv

> Please think before you post again. If the motor was an open brush type motor let us say your wife could smell gas, what does she do, she turns the range hood fan on to clear it. Now there could be a pocket of gas is in the range hood so the spark of the motor brush would ignight that and the hood the flue and your wife would take a trip very quickly. If you have built such a unit I advise you to get rid of it.

  Maybe you should think before you post. You obviously don't know what you are talking about :
1. I don't think I have ever seen a brush type motor being used in a domestic blower or fan - they are normally shaded pole motors.
2. My wife is obviously smarter than you give her credit for - she would know that LPG is heavier than air and sinks and as such turning on the range hood would do little. If we had a gas leak (LPG as we use or NG if is was available) she would shut off the electricity and gas, and open all the windows and doors.  
I enjoy a good debate as much as the next person, but your responses are becoming quite tedious. So do you have any valid points to argue or are you just clutching at straws?

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## murray44

Plum, 
Beware, apparently a new style of 'inverse chimney' which drawers air from the top (not the bottom) has been invented.
Rrobor will be able to fill you in on how it works. 
Murray

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## watson

Its me again.........
This is going around and around....and as I've got to read each post.....well........
I'll leave you with this pleasant interlude......by Taj Mahal/The Nitty Gritty Dirt Band and lots of friends 
Will The Circle Be Unbroken............  My Bloody Oath! 
[ame="http://www.youtube.com/watch?v=GJpCKi1RWLs"]YouTube - Will the Circle be UnBroken pt 3[/ame]

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