HRV and fire spread

Excellent idea... well done!
I agree that we should all read the draft documents and make comments, to the Building Standards Section where necessary.

By the way there was an issue raised on another Forum, as regards Heat exchanger and house fire.
It was felt the heating & ventilation exchanger might spead smoke around a dwelling unless they could be automatically turned off, once the fire alarm activated.

Would it make sense to maintain the extraction function of the unit?
Extracting toxic smoke from the dwelling. Maybe increased suction could be activated by the smoke alarm. Surely it could be done electronically without much alteration to the unit ( I'm no expert in this field ):)

I can only agree with sinnerboy's warning. On the continent ALL air containing ducts, no matter what their original pupose is, must be equipped with fire proofing material and fire/heat/smoke detectors if they connect two or more separate apartments/houses . Not only they have to have alarms and emergency switch-offs build in they must contain as well so called "fire-flaps" which close automatically.If there are rooms supplied with both-airducts and open chimneys- then more specificated precautions have to be taken. The min. fire ratings of materials must not be altered with. These fire ratings are the only "life boat" in single homes/appartments where stricter building regulations are not in force-yet. EN standards are propably already being upgraded to deal with the European wide increasing number of air duct installations. Be prepared and don't put money into an installation that might be outdated tomorow.

Good Point sinnerboy, in commercial buildings ducts going through fire resisting construction, wall / floors etc have to be fire stopped and have fire dampers, there's a large section of B3 in the TDG B dealing with it. HRV ducts and any other system that is passing through fire resisting construction in a dwelling house should be dealt with accordingly. Any fire officer I've talked to over the years has always siad they'd like more power / controll in relation to dwellings as most of the fatalaties from fire in this country are in dwellings.

You're right, with a standard HRV system the two flows are seperated by the heatexchager. Larger installations as in shopping centers doe however mix the fresh air with a certain amount of stale air to save on costs for cooling or heating.
Blowing fresh air into a fire spreads the fire of course, oxigene is THE fuel for a fire. As a general rule the doors and windows in a burning building should be kept close to hinder the fire by eliminating oxigene as well as hindering the fire/heat spreading from one room to the next. As well the smoke should not be allowed to spread.
Most ducting in household aplications is not fire prof, so hot gases not saturated enough with oxigene sucked up by the HRV and then mixed with air(oxigene!) at the next junction can lead to a flash-trough phenomena, highly explosive gases will ignite by adding oxigene and flash through all the ducting. Shooting down into all rooms connected to, igniting all rooms at once like a flame gun held into the ducting.
This is the major risk when no fire flaps are build in. The fast,sudden spreading of heat and smoke.These flaps close automatically, either triggered by heat, smoke or by the sudden pressure increase of the flash-through (an explosion!) itself.

Hm, I'm not sure what you mean by "better products"?In principal an airsuply/ventilation system should be checked or comissioned by a fire inspector, someone who is actually trained. On the EU continent every larger city/community has one available to be called out.I supose if you call to the local firebrigade they'll will have a number for you to call.Civil engineers might be able to help as well.In larger buildings-where ducts are passing several independant units/rooms-airsuply ducts in new buildings must be explosive proof, propably fitted with an emergency outlet opening if a flash-through/explosion happens. Otherwise the entire ducting system might be ripped apart and the whole building will be set on fire at once.Ducts should be made as well of a fire proof material in larger buildings, not only air ducts but sewers as well. Steel, fibre cement etc..

One detector for the unit to switch it off-that is the logic solution. Having a dozen or more dampers in the house all connected to the ventilation unit via wires makes the system very expensive and unsafe in itself. The dampers themself are an obstacle in the air transport system b.t.w., the system has to work harder to get the necessary amount of air passed. But with dampers the build-up of combustable gasses and their sudden ignition within the ducting can't be stopped.And this would mean a flame thrower/-gun hitting into all rooms incl. the (ventilated!) rescue paths at the same moment . Setting the entire house ablaze within a second. Consuming all present oxigen.Blowing out the dampers like champagne corks.Gases don't have to be hot or soot enriched to be explosive.So neither room dampers or smoke sensors or heat sensors will hinder the ignition of a gas filled duct. This simply can't be avoided. But the consequences of this ignition can be calculated and influenced. One can't use the cheapest live vest of course. Only a fire proof ducting material capeable of withstanding a sudden increase of pressure which includes self-triggering flaps (triggered by vibration and gravity)in combination with overpressure outlets at the building (we're talking about a gas explosion within the ducting after all!) are a halfways safe method to avoid a sudden ignition of the entire building.And if smoke alarms are installed all the better.Using the cheapest available gimmic and adding it to a cheaply constructed ventilation system is certainly not the best available method. And certainly not safest as well.

This thread has ended up a 2 horse race. I cant see any good reason to leave it open as I think the "arguments" will only end up being repetitive and dare I say it - boring when it gets to that stage.

Thread locked.