Gas cookers and airtight houses

[1not24get]

Just wondering could anybody point me to a source that might be able to shed some light on this topic…..I will be building an airtight house (airtight to passive house spec <0.6 ach/hour at test pressure) but the Mrs loves cooking using a gas hob. I’ve done some reading on the internet and the main concern with using gas in any house is the accumulation of combustion gases (nitrogen dioxide and carbon monoxide). Studies done to date indicate that in many ‘houses’, levels of these gases exceed WHO safety levels. I suspect these studies were carried out on ‘traditional build’ homes and not airtight ones. My question is if I were to use a gas hob in an airtight house with MHRV would this be dangerous? It seems as soon as ‘airtight’ is mentioned people freak out at the thought of using gas when it seems before nobody ever paid much heed to combustion gases when building a traditional house. Would the MHRV make the house safer than a ‘traditional build house’ because with MHVR the air exchange is continual and not irregular or variable as with traditional build houses??

[Scaffolder]

I always thought a backup battery system for the MVHR like used on pc's would be a good idea for when the elec goes down, maybe with a small alarm with one of those annoying voices saying open a window. Especially for the elderly also, many people would not have the commom sense to open a window when the power goes.

[heinbloed]

When using gas cookers in a closed building then two major points has to be looked at: the cooker should have an automatic off-switch that would cut the gas suply in case the flame is stoped by over-boiling or an accidental turning of the switch. And the cooker should be equipped with a capeable extractor hood.
For CO (carbonmonoxyd) emissions there is not much of a problem with a proper installed cooker. As long as the flames are blue-clear in colour the combustion is "clean", there would be hardly any CO emissions with such a flame. But if they're yellow/orange then there is danger, ventilate!
My house is build airtight and I'm using an LPG cooker(4 flames, sometimes all paralel) and I have a CO detector installed next to it. I never had an alarm exept for test purposes. But I also have a cooker hood and a cat flap. When the cooker hood is turned on the cat flap automatically opens and avoids therefore a vacuum within the house created by the suction power of the hood.
So in general: as long as the ventilation is working you can use a gas flame.

[1not24get]

That’s good news Heinbloed…will keep the Mrs. happy! Yes I had a problem with our gas hob...a yellow flame blackening all the saucepans....couldn’t figure it out for months until my brother pointed out that there are different sized nozzles for the hobs using bottled gas (butane) and piped natural gas (we use bottled gas...cooker was set up for piped gas)....went back to the 'experts' in the shop were my wife bought the cooker (BTW we and the shop are in the north-west…no piped gas here for 200 miles!)…they claimed the correct nozzles had been fitted and wasn’t their problem etc. etc...so I had to buy the correct nozzles and fit them myself and since then blue flames and no more black saucepans....as with everything...if you want it done properly do it yourself!!


the cooker should have an automatic off-switch that would cut the gas suply in case the flame is stoped by over-boiling or an accidental turning of the switch.

What is this? Is it standard on gas cookers here in Ireland?


My house is build airtight and I'm using an LPG cooker(4 flames, sometimes all paralel) and I have a CO detector installed next to it. I never had an alarm exept for test purposes. But I also have a cooker hood and a cat flap

Do you have MHRV and how airtight is your house? Is the ‘cat flap’ a pet cat flap in the door or a little vent in the wall beside the cooker? Sorry for all the questions just trying to compare like with like.

[1not24get]

BTW I read on another forum about a guy who had a kitchen/toaster fire in an airtight house with MHRV…afterwards the fire officer pointed out that the MHRV system should be connected to the fire/smoke alarm so in the event of a fire, it cuts out so it does not keep supplying the fire with fresh air therefore making the fire worse.

[CCroly]

You can get a carbon monoxide sensor in B&Q for about €20 which also has a smoke detector in it. It has the added advantage of letting you know when the food is ready (at least it does when I'm cooking)

[1not24get]

You can get a carbon monoxide sensor in B&Q for about €20 which also has a smoke detector in it. It has the added advantage of letting you know when the food is ready (at least it does when I'm cooking)

Excellent......I like it

[heinbloed]

Hi 1not24get!
The automatic switch-off mechanism isn't standard/demanded by law-yet. But all major manufacturers have them in stock, some have only these cookers/stoves. In principle it works like a bi-metall, as long as it is heated up by a flame it opens the gas suply and if it cools down it closes the suply. Ask in the white ware shop for cookers with this safety feature, they have them in stock.
Check the manual or ask the suplier/manufacturer of your hob if it is present. Otherwise check it out:switch all electric apliances off(fuse box!)) and open the windows. Then turn on the smallest fire at the hob and blow it out, use your lung bellow(smiley). And then simply wait for a while. If the gas still comes out after 60 seconds then either there is no safety valve installed or it is defect.
The cat flap I have installed is a real one, for a real cat. It (the flap) has a magnetic lock, so a simple blow of the wind won't open it, making the house more airtight then just a flip-flap.This magnetic flap won't open at the lowest cooker hood setting either, it needs some force, setting "4" at the hood to open it, after that the hood setting can be reduced to"3".
How airtight my house is is hard to say, there was no pressure test done. But the phenomena of the opening catflap astonishes most visitors, incl. the cat.
For an average sized kitchen it will take hours of cooking on the gashob to make the air"thin", to reduce the O2 level down to a dangerous level. So even without a cat flap you should-in principle- be save. But when using a source of open fire it should be the rule to have a proper ventilation in place.CO2 from the combustion is without smell, accidents do happen.
All centralised air suply/exchange systems should have fire-flaps build in. By law they aren't demanded for single family homes, but for apartment buildings and all public buildings they are legally demanded.These fire flaps are either activated by smoke,heat or CO sensors. Usually they not only close the ducting and switch off the air pump but they also raise an acustical alarm.