Carbon Minoxide and the Home Part 3

In late January of 2012 the Globe and Mail ran a far too short article on a family of 5 who died from CO poisoning in Whitehorse Yukon.  The reporter gave sparse details, only mentioning that the home had a wood/oil furnace. But that really says nothing.  Some might assume that the heat exchanger was cracked. This may allow CO gas to enter the home via the duct system.  But that really does not always lead to CO tragedies when that crack is small.  This kind of furnace is not so effcient when it does burn its fuel so some CO is being manufactured.  CO is only manufactured when the process of combustion of a carbon based fuel is incomplete.  But this would not necessarily enter the home via a duct work.  CO can be leaked out of the vent stack.  Such an accident took 5 lives in Woodstock Ontario last year.  There also might not have been enough combustion and dilution air in the basement to burn the flame cleanly, and to cause a draft to pull the exhaust fumes up the metal vent.  There could also be a depressurization of the house that caused some backdrafting and sent CO gas into the living quarters.  The point of stating some other possibilities is that we do not in general know enough about CO and the home to be adequately educated about CO and home safety.  The reporter only hazarded a lame trial balloon that said nothing.  And too many people really do not know about the sources of CO, and what to do about it.  

There are plausible sources of CO.  Any open flame can release CO as a byproduct. The more obvious ones in the home are just about any kind of furnace that is not electrically fueled.  So gas conventional, mid and hi efficiency funaces are the obviouce choices.  It also includes propane, solid fuel, and oil or combination furnaces of solid fuel and oil usually.  But fireplaces, wood stoves, and all gas appliances: stoves, dryers, and hot water heaters if they are not electrically fueled have CO manufacturing possibilities.  Space heaters that are not electric can produce CO as well.  To confuse things appliances like smoking BBQs where we see no flame, and smouldering fireplaces  are more dangerous CO producers than flames that we can see. The Key here is that CO is produced by incomplete combustion.

The metal vents and chimney flues can release CO if they are cracked or rusted, or displaced.  What we have done is try to identify plausible mechanical sources.  It should be noted that a smouldering flame in a fireplace or a BBQ system is far more dangerous than a hot flame licking the air with gusto.  Hvac( Heating/ventilation/air conditioning) TSSA ( Technical Safety Standards Association) people and WETT( Wood Energy Technology transfer) technicians approach CO home safety largely from a mechanical appliance; and exhaust and intake vent perspective.  Vents that are plugged by nests, vermin, debris, lint can also cause CO to be built up.  In a gas dryer lint can cause CO to be manufactured as there is not a clear air way exhaust release.

Firefighters have CO knowledge from their portable CO monitors, their knowledge of increasingly dangerous CO levels in PPM, and health effects from a variety of health organizations that weigh in on CO and the air we breathe.  They also know a lot about human physiology and how CO is carried into our bloodsteam and impinges on health. That can lead to death through asphixiation when enough CO enters into our bloodstream.

There is a third body of knowledge that is neccessary here.  Besides the mechanical appliance and its venting, and CO levels of health  and warnings, the actual physics of a home: building sciences plays an important role.  Not all HVac pesonnel may carry a complete body of knowledge on building science, and Fire Fighters are perhaps less likely to integrate this sector that needs to be addressed in assessing CO poisoning potiential and the home.

Hvac personel can tell you that if you have older conventional natural draft furnaces and water heaters( older high efficiency furnaces also relied on air brought in from the outside but it was not sealed or fan induced so they were in some ways affected by the pressure differences between the inside and outside) for each 1000BTU you need a certain amount of ambient air available to create clean combustion and exhaust updraft.  They may also tell you that larger fans in the kitchen can create pressure depressions that can cause exhausted air to re-enter the bulding envelope or living quarters.  But there are also other considerations.  Temperature differences between inside and outside and wind blowing on an exposed house create leeward walls that draw air out of homes rather than cold air into a home on the leeward side of the home.  This causes utility rooms that are to supply air for natural draft furnaces and hot water hearters to empty causing the combustion process to suffer and poisonous exhaust air to renter the bulding through backdrafting and combustion spillage. 

Are there tell tail sings of CO. Older conventional furnaces have draft hoods that will show blackened, sooty or scorching signs.  Hot water tanks will have similar signs on the tops surface immediately below the vent intake.  Fireplaces may have similar markings on the top of the brick work of the screen of glassed cover.  Ceilings may also be discoloured.  Living quarters may smell a bit smokey.  But leaks in chimneys and metal vents will show nothing.  Built up CO2 from a space heater has less Oxygen available so when it starts to produce an escalated CO because of compromised combustion we see nothing as well.  You will not also see if a gas stove element is producing CO.  Remember CO is a "silent killer".

When a home inspector looks into a furance where a heating chamber can barely reveal 5% if that of the heat exchanger, seeing a crack is about as likely as winning a lottery.  And its sigificance needs a referral to a TSSA qualified technician.  The most responsible thing for a home inspector to do is to have a portable CO monitor that tells the client about CO, and if it is detected in other parts of the house, room by room.  As a client, you should ask for it.  The body of knowledge that is required here begs for an education process similar to fire safety plans for the home. And home inspectors may be the only people who should know the various components of CO production and the Home to do this.

We will tackle CO detection itself next.  And this too has its controversies.

Remember:  A home inspector is a Good Looker!... and a good educator. They should carry a portable CO monitor and be able to educate you on CO safety in your home.

Kurt Weinberger: home inspector for EnerGREEN Home Inspection Services - serving Kitchener, Waterloo, Cambridge, Guelph, Brantford, Milton and Mississauga and surrounding areas. Contact me through kitchenerwaterloohomeinspector.ca, 519-888-0852, kjweinberger@rogers.com