Rangehood Duct Material Requirement (Domestic)

Dommal on 05/04/2021 - 08:21

Hi all,

I have a general question about a fire standard in VIC for domestic buildings after experiencing what I see as a near miss of a serious house fire. In this case an oil fire on the cook top (gas) could have ended in a fire inside the wall cavity. More detail below.

Background:
Smeg Rangehood (stainless steel filter) - Flexible Plastic Duct (black inside/silver outside, feels like a bin-liner with wire mesh)
Smeg Natural Gas Stove
Wall exhaust 'grid'

Last week the oil in the frying pan caught fire and the flame went high enough to get sucked into the filter (fan was running). Since there was unusual noise afterwards I've removed the rangehood cover to find a completely disintegrated duct (only a remaining wire skeleton).
On top of that I've noticed that the duct was not attached to the wall, only placed near the wall outlet, so a lot of grease accumulated already inside the wall cavity around the insulation, which also looked slightly burnt.
Shortly after the 'thermal event' we had our one year inspection and I've raised the issue with the builder who just waved it off ass 'it's the standard duct that comes with Smeg appliances'.

I was skeptical enough to call Smeg and they've confirmed that they don't supply ducts with their Rangehoods…

So I'm trying to work out if there is a AS that clearly specifies which material Rangehood ducts are to be made of. The one in our case is definitely out of flammable material, as I've ignited a piece of it and it burnt to ashes 100%.

Side note: When I bought a replacement at Bunnings, I was told that the only option they sell is made 100% of aluminum with a fire rating of 4.

Maybe somebody with fire safety experience can help and clarify what the material for this case is supposed to be so I have a bit more leverage to ask the builder to cover the costs of the replacement duct and the tradesmen cost to fix the wall (had to cut a big hole).

Cheers

Home & Garden Rangehood

Comments

  • Austaurean on 05/04/2021 - 08:34

    While i don't have an answer, i do thank you for bringing this issue to the forum. It is good to know…

  • bloom on 05/04/2021 - 08:38

    My Bosch one came with the usual plastic foil duct

  • Jimothy Wongingtons on 05/04/2021 - 08:46

    My delonghi one came with a plastic foil duct too but now I too wonder the safety implications…

    Thankfully we no longer have house mates - we don't shallow/deep fry so i suppose the danger is low/non-existent…

  • Lexus101 on 05/04/2021 - 09:18
    +1

    I believe the plastic ones will melt when faced with high heat event as in OP's case.

    Would recommend using "Aluminium Semi Rigid Duct" which is way stronger and hopefully better flame or oil resistant.

    I re-ducted my hood with the Pacific Air branded aluminium ducts bought from Bunnings. Also remember to use only the aluminium collar extenders to join 2 ducts together if more length is required.

    Thanks for posting OP. Stay safe.

    (PSA Here: Winter is coming. Folks using old gas heaters. PLEASE get a Carbon Monoxide monitor. Life is Precious).

  • AndyC1 on 05/04/2021 - 10:07

    15 years ago the ducting that came with a Westighouse range hood was aluminum (no plastic anywhere).

  • Stewardo on 05/04/2021 - 10:37

    How high above the stove is the base of the rangehood? Should be 700+

  • Typical16-bitEnjoyer on 05/04/2021 - 11:23

    Ok, what is a "Wall exhaust 'grid'"

    Practically every range hood manual will tell you flues are not included and if an install is not properly flued that you need to buy charcoal filters.

  • errorius on 05/04/2021 - 12:53

    Flexible is ok for domestic. Usually it's blowing air in to the roof void unless you have dedicated kitchen exhaust system.
    Domestic has to be rigid connection off the rangehood.
    I personally would avoid semi-rigid if it's not blowing air directly outside of your house. Imagine it being full of grease and catching fire then shooting flames inside your roof void.

  • thatonethere on 05/04/2021 - 13:22

    the flexible aluminium tube stuff is only "fire resistant" but as any kid knows it will catch fire eventually and an oil/fat fire will set it on fire.

    Smeg actually say if you have a fire under your rangehood you will have a fire hazard: quote" Do not flambè under the range hood; risk of fire "

    What model of rangehood did you have? Was there no grease filter or equivalent to stop the flames going into the duct?

    I recently had to replace the motor in our rangehood (good old Aussie one) and noticed that it was all steel ducting - it was a real pain as you had to buy all the pieces from Quasair when we moved it for a reno but they were good guys to deal with. It was a little greasy when we moved it (was about 12 years old of fairly solid use - but I wasn't able to clear it).

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