In the middle of a cold winter day, the last thing you want is for your furnace to stop working. Unfortunately, furnaces can malfunction when they're needed most, simply because their vents become blocked with snow, ice, or frost. However, there's a good reason why many furnaces shut off when their vents are blocked – it's a built-in safety mechanism. Without proper ventilation, carbon monoxide can build up inside the house, the consequences of which can, at worst, be fatal. As a result, many furnace manufacturers design their units so that they shut off automatically when the vent becomes blocked.

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Even if your furnace is running, there's a possibility that its vent could be partially blocked. Over the course of the cold winter months, frost can build up slowly in and around the vent, reducing your furnace's efficiency. A furnace vent can also become blocked by a buildup of snow or ice. So whether it's for optimal efficiency or protection from carbon monoxide, it's important to keep your furnace vents clear. Here's how to do it.

Dealing with Frost

If the temperature outside remains below freezing for a few days in a row, it's time to inspect the furnace pipe vent on the outside of your house. It's usually a white plastic pipe that comes out of the side of a house. If you find a thin layer of frost on the pipe, you can scrape it off with a plastic putty knife. Next, use a flashlight to look into the pipe vent to see whether there's any buildup on the inside.

If there's a heavier buildup of frost, you'll need a source of heat to get rid of it. One way is to plug a hair dryer into an outdoor extension cord. Turn up the dryer to its highest setting and use the hot air to melt frost inside the pipe. Remember to keep your hands safe and wear protective gloves while you use the hair dryer.

While the hair dryer is a handy tool for clearing frost, don't ever use it in the rain or during a snowfall, as it poses a risk for electrocution.

Clearing Snow

Check on your furnace vent during and after heavy snowfalls, and clear snow away from the vent's opening if it builds up. If you do notice a mound of snow blocking your furnace vent, clear it away by hand – don't use a shovel or a snow blower, as either could cause damage to the furnace vent pipe.

Don't Forget the Meters

Just as with a furnace vent pipe, gas and electric meters can malfunction if exposed to frost, ice, or a buildup of snow. A malfunctioning meter can cause your heating system to run less efficiently, or shut down altogether. While you check on your furnace vent, it's a good idea to have a look at your gas and/or electric meter as well, and ensure that it's free of snow, ice, and frost.

Restarting your Furnace

If your furnace shut off as a result of a blocked vent, restart it according to the manufacturer's instructions after you've deal with the blockage.

On average, fifty people a year die in Ontario unnecessarily from Carbon Monoxide poisoning. While it's mandatory to have carbon monoxide detectors in all homes now, they are not 100% reliable (they become unplugged, they might not be in the right room, etc). This is why it is important for you to take every step to ensure your furnace is being properly vented. Dryer vents also need to be checked too. During heavy snowfalls, be sure to check your dryer vent to ensure that it has not been covered with snow before you use your dryer. If it has, dig it out by hand and make sure the exhaust fumes can escape your home.