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Why should you care about your Furnace Air Filter?

Updated: Aug 20, 2019



If you own a house, you've probably encountered the furnace filter before. Easily forgotten, and yet an incredibly important part of the system, the filter protects dust, hair, and debris from entering the furnace blower fan. It's easy to tune out your furnace, but we'll talk about why it'll save you money, and possibly your life, by just giving it the attention it needs.

Depending on the quality of your air filter,it will have a different effect on the air travelling through your house. Filters have a MERV, which stands for Minimum Efficiency Reporting Value, that tells use how well they catch dust, pollen, and dirt. MERV values begin at 1 and go up to 16, but these higher rated filters are generally used moreso in high allergen situations, and aren't necessary in your average home.

Another thing to take note of, your filter can create a dangerous, and costly situation. It can lead to the destruction of your furnace or even a death. As your furnace blower fan pulls air from your return duct, down through your air filter, over time the filter will allow less and less air through it, as it becomes more clogged with dirt, etc. What most people don't know is that when your furnace is running, and the filter hasn't been changed in a while, it may have a hard time moving air past the furnace, which makes the furnace get incredibly hot to the touch, which is bad. Usually as the furnace warms up and prepares to heat your house, it pulls air from the return duct, and blows it past the furnace heat exchanger, keeping the furnace at a warm and controlled temperature, while heating the air in your house.


Remember we are literally playing with fire inside of this metal box in your basement, let's not forget that.


If the furnace filter becomes clogged, and goes unnoticed, the furnace will begin to "Short Cycle" which means that it will ignite the gas, heat up, but not be able to move enough air (because our filter is clogged) which will cause the furnace heat exchanger to get very hot.


Too hot. If this process is allowed to repeat multiple times, there is a high change that the heat exchanger will develop a crack. Once there is a crack in the heat exchanger, your furnace is basically garbage. It's costly to replace just a heat exchanger and in your average residential home, you would most likely replace the entire furnace to benefit from the 10 year warranty.




There is a safety called a "High Limit" switch. This switch will automatically trip when the temperature gets too high inside of a furnace. Any part can fail though, and if this "High Limit" decides to stop working, now we have a very unsafe situation. As we've already discussed, a dirty filter can lead to a crack in a heat exchanger, and without the proper measures in place such as a CO (Carbon Monoxide) detector, a dirty air filter could actually lead to the death of a yourself or a loved one. Every home should have several CO detectors. One on every floor at the very least. It is mandatory in Ontario. You can get models that plug into an outlet, or that are hard wire in, like some smoke detectors.





You can purchase higher quality filters that will do a better job of preventing more dust and hair from spreading for people that suffer from severe allergies.


So which filter should you buy? Most people have the standard 16" x 25" x 1" air filter rack installed with their furnace. The best place to buy them is online, as you can buy in larger groups and save money. But you really can't go wrong even with Canadian Tire or Home Depot. You will find the prices of filters range anywhere from $10 or $25 each, all the way up to over $50 each. For the average person, you just need a basic filter, don't worry too much about price and quality.


It's much more important you either set a reminder, or remember to check on the filter every month. Once you get into that routine of checking the filter, you will start to notice a pattern of when you need to change it. Rule of thumb is if you hold the filter up to a light source and can see the light fairly clearly through it, then it's still good. But if you are every unsure, for the cost of a filter versus your safety or furnace replacement, it would probably be smart to change it anyways to be sure.

Below are a few links to different filters on Amazon. You can see based on the different prices, and MPR (Micro Particle Performance). I would recommend buying a couple different MPR rated filters, and trying them out. But in the end, I think you'll find the less expensive versions are just as good as their expensive counterparts.


Filtrete Pleated MPR 2200 16 x 25 x 1 - $52 for pack of 2 - CLICK HERE

Filtrete Pleated MPR 300 16 x 25 x 1 - $48 for pack of 6 - CLICK HERE

Filtrete Pleated MPR 1500 16 x 25 x 1 - $99 for pack of 6 - CLICK HERE

Filtrete Pleated MPR 1900 16 x 25 x 1 - $146 for pack of 6 - CLICK HERE

Aerostar Pleated MPR 600 16 x 25 x 1 - $45 for pack of 6 - CLICK HERE

Nordic Pure Pleated MPR 1700 16 x 25 x 1 - $54 for pack of 6 - CLICK HERE

United Filter Pleated MPR 600 16 x 25 x 1 - $89 for pack of 12 - CLICK HERE


Hopefully this helped shed some light on the importance of changing your furnace air filter, it will make your system last long, will make your house safer, and save you money!


Have you been ignoring your filter?



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