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In the thread on humidifying your home, Fred got bashed because of his warning about the possible dangers of CO poisoning in your home. Somewhere during the discussion, personality clashes overshadowed the message. The MESSAGE is that this is a growing problem and we have to be alert for situations that could endanger building occupants.
I am aware of at least three instances recently, where occupants of homes and small office buildings were sickened by CO being backdrafted out of gas burning appliances. All of these occurred after extensive remodels, where the building was tightly sealed to the standards we see in most new homes. The problem occurred with natural draft venting (as opposed to power vented appliances). With the installation of new fans in bathrooms, kitchens etc., or leaky return ducts, it is very easy to depressurize a structure and backdraft out of flues.
The areas where I work now require a 6″ makeup air duct with a balancing damper on it in all new construction to help prevent this problem. The irony is that the problem is not nearly as serious in new construction where almost all gas burning equipment is power vented, but in remodeled buildings with existing older draft vented heaters.
My advice….If you have recently done a lot of air sealing on your home and still use the older heating units, close all your windows etc., turn on your fans and have someone check the draft in your appliances while they are running. It could save your life!
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I agree. In reworking the flue for our water heater & furnace, I was surprised at how fragile the balance is that will assure proper venting. A miscalculation (or, as is more often the case, failure to calculate at all) could lead to serious backdrafting. A poorly tuned or oxygen-starved appliance will produce a lot of carbon monoxide. Oxygen starvation prevents complete burning of hydrocarbons (CH chains and rings) to the stable CO2 and H2O waste products. CO is highly reactive and poisons your blood by permanently deactivating hemoglobin, binding more tightly than CO2. The only way your body has to recover from CO poisoning is to dump the old cells and produce more red blood cells.
Besides natural draft and power vent (sealed) appliances, there is also a class of "fan-induced" draft. Our mid-efficiency furnace is one -- basically it relies on the fact that heat rises for its draft, but has a fan to nudge things in the right direction. These appliance too are vulnerable to backdrafting.
Realistically I think backdrafting happens all the time, usually intermittantly depending on variables such as the speed/direction of the wind, the temperature of the flue, which doors are open, etc. In a leaky house the CO is more likely to be flushed out, the appliance room is not depressurized, and the appliances are less likely to be starved for oxygen. And of course people can take a certain amount of poison without effect, though you don't really want to do it. The CO detectors sound only after lengthy exposure to low levels of CO, levels that are nonetheless mildly toxic.
Don't forget about cracked heat exchangers, too! The former landlord here had to buy the new furnace when a busted exchanger drove the renters out into the street in the middle of the night (fortunately some people, myself included, get sick to their stomachs when exposed to carbon monoxide -- others just pass out quietly).
*Thanks for the post! This is a subject that has been ignored too long.It is just becoming widely known just how toxic the interior of a home can be. There are a wider variety of gases vented into the home from appliances, furnishings, building materials, etc than what the general public knows.Carbon monoxide is one of the most immediately deadly and can also come from an attached garage.Your recommendation to Test and Monitor is right on target.
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In the thread on humidifying your home, Fred got bashed because of his warning about the possible dangers of CO poisoning in your home. Somewhere during the discussion, personality clashes overshadowed the message. The MESSAGE is that this is a growing problem and we have to be alert for situations that could endanger building occupants.
I am aware of at least three instances recently, where occupants of homes and small office buildings were sickened by CO being backdrafted out of gas burning appliances. All of these occurred after extensive remodels, where the building was tightly sealed to the standards we see in most new homes. The problem occurred with natural draft venting (as opposed to power vented appliances). With the installation of new fans in bathrooms, kitchens etc., or leaky return ducts, it is very easy to depressurize a structure and backdraft out of flues.
The areas where I work now require a 6" makeup air duct with a balancing damper on it in all new construction to help prevent this problem. The irony is that the problem is not nearly as serious in new construction where almost all gas burning equipment is power vented, but in remodeled buildings with existing older draft vented heaters.
My advice....If you have recently done a lot of air sealing on your home and still use the older heating units, close all your windows etc., turn on your fans and have someone check the draft in your appliances while they are running. It could save your life!