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All About Central Air Filters
Why Does My Central Air Have Two Filters?

Let’s say you just moved into a new house 3 months ago, and it is time to change out your air filters. You go to look in the usual spots for air filters, and to your surprise, you find filters in multiple locations! Confused?

How Central Air Systems Work

If you have a central furnace and/or AC system in your home (as opposed to ductless systems), then your system is composed of multiple parts:

Understanding the parts matters because it can explain cases of multiple air filters being used

When You Need Two Air Filters

There are multiple cases when multiple air filters are needed:

When Two Air Filters Is a Bad Idea

Lastly, while this is not a common scenario, it’s worth calling out this piece of advice from a Houzz forum discussion – if you see a return duct that can accommodate a 2 inch or 4 inch air filter, but has multiple 1 inch filters stacked on top of one another to fit the slot, get rid of this setup immediately. It is questionable if it works the same way as one 2-inch or one 4-inch air filter in terms of filtration effectiveness in working with your central air system. Additionally, its more expensive to buy Air filters this way. For example, a 16x25x1 air filter costs $22.66* if you buy two filters – by contrast, buying one 16x25x2 air filter costs $17.58* - a much better deal.

* pricing is current as of 8/16/20 – prices may have changed since the publishing of this price

Changing Your Air Filters

Now that you know where you must look to find all your air filter replacements, you are on your way to breathing freely in your home. If you find you need multiple air filters, you don’t need to buy from multiple stores – simply find your sizes and your central air system brand on our site to buy the type and quantity you need. If it’s your first time installing air filters, make sure to read up on these resources to buy the right products and get it working correctly: