How many filters does a furnace have?

Author: Coty Dickens  |  Last update: Saturday, November 15, 2025

Typically, a house will have 2 air filters in their intake vents. In some cases, there can be more or fewer depending on the square footage of the home or apartment and the number of floors that need to be supported by the central air system.

Does my furnace have two filters?

Yes, an HVAC system can have two filters.

How do I find where the filter is for my furnace?

The blower compartment's (bottom door) next to the cold air return is where you'll find this filter. After removing the top and then the bottom doors, you must replace them in order. Check that the bottom door is properly secured over the furnace frame and switches on the safety device.

How many filters does a furnace need?

Essentially, most homes will have at least two air filters, because most homes have a return duct to go along with their air handler.

Do I need both a furnace filter and a return air filter?

Do I need both a furnace filter and a return air filter? Most HVAC systems only require one filter, usually located at the return air vent, to capture particles before the air reaches the furnace or AC.

Furnace Air Filter - How to Change It Properly

What happens if you install furnace air filter backwards?

What problems can a backward filter cause? The most common thing you will notice is the inefficiency of the filter. It will be harder for the air to flow, which would take a toll on your system. More strain means spiked utility bills.

How often should furnace filters be changed?

For 1- to 2-inch filters, replace them every 1 to 3 months. For 3- to 4-inch filters, replace them every 6 to 9 months. For 5- to 6-inch filters, replace them every 9 to 12 months.

Will my furnace be OK without a filter?

Your furnace can, technically, run without a filter. However, we strongly recommend you don't run your furnace without a filter for any length of time. With air constantly moving through your furnace and your home, dust and debris can quickly build up, even in a matter of minutes.

How long does a 1 furnace filter last?

Our standard recommendation is as follows: For 1- to 2- inch filters, replace them every 1 to 3 months. For 3- to 4- inch filters, replace them every 6 to 9 months. For 5- to 6- inch filters, replace them every 9 to 12 months.

Do all return vents have filters?

While return vents don't always require filters, adding them provides additional filtration, improving indoor air quality and keeping dirt and debris out of your system. However, there are pros and cons to consider.

Do all furnaces have a filter inside?

Do All Furnaces Have Filters? Yes, all furnaces & heat pumps have filters. If your home uses another type of heating system, like a boiler which uses water to heat the home, you will not have filters, but for a furnace or heat pump, a filter is a vital component.

Where is my furnace filter carrier?

However, common places filters are found can include: within a small slit on the bottom of the unit, on an external rack usually off the side of the furnace, in the ductwork as a cutout, or in the return air vents. If you are unable to locate your filter, please contact your dealer or installer.

Why is my furnace blowing cold air?

With a furnace blowing cold air, the first question you should ask is if the furnace has been turned ON. Two thermostat issues that could cause your furnace to blow cold air include (1) your thermostat is still set to COOL, not HEAT and (2) your thermostat fan is set to ON, not AUTO.

How many air filters are in my house?

How Many Air Filters Does a House Have? Typically, a house will have 2 air filters in their intake vents. In some cases, there can be more or fewer depending on the square footage of the home or apartment and the number of floors that need to be supported by the central air system.

Is it OK to double up furnace filters?

In conclusion, while the idea of stacking two filters might seem like a shortcut to better air quality, it can lead to more harm than good.

How can I tell if my furnace filter needs changing?

Signs Your Furnace Filter Needs Changing
  1. There is noticeable discolouration on the filter.
  2. You can see the buildup of dirt and dust.
  3. You find your home needs dusting frequently.
  4. It seems your HVAC system is cycling longer.
  5. You realize it's been several months since you've replaced your filter.

Can I leave my furnace filter out for a day?

You can run the furnace without installing a filter, but only temporarily (such as overnight, awaiting a new filter). If you let it run very long without filtration, contaminants will build up.

Can I run my AC without a furnace filter?

The short answer: You can get away with running your AC without a filter for a short period of time. However, doing so for longer than 6-8 hours can hurt your system and decrease your home's indoor air quality.

Will my furnace shut off if filter is dirty?

If your filter becomes clogged, it can cause your furnace to shut off as a safety feature to prevent damage to the furnace. To fix this problem, simply replace your air filter on a regular basis. If you have pets, be sure to change your air filter more frequently.

Do I have to turn off my furnace to change the filter?

The first thing you'll want to do is shut off your HVAC system. You should always avoid changing furnace filters while running the heating system, as various types of debris can enter the furnace — and you certainly don't want that to happen.

What happens if you never change your furnace filter?

This leads to a variety of issues for your HVAC system including system inefficiency, higher energy bills, inadequate air quality, and ultimately failure. If you haven't been swapping your air filters as frequently as you should, there's no time like the present to start practicing this crucial maintenance step.

Do more expensive furnace filters work better?

The higher the MERV rating, the better the air filter is at removing particles. Cheap air filters typically have a low MERV rating of 6 or less, while expensive air filters can have a MERV rating of up to 13. This means that they can remove much smaller particles, like bacteria, viruses, and mold spores, from the air.

How many hours does a furnace filter take?

These particular types may not last as long as other individual components, but they can be cleaned and reused for a longer time frame. Replacement filters vary in their lifespan from model to model. However, these usually need replacement every three months or after 200 to 300 hours of usage.

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