Is My Air Filter Too Small?

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How to determine if your air filter is the correct size for your unitIs the air filter I have too small for my unit? We hear this question from a lot of our customers. Each air conditioning system or HVAC unit has a certain size filter that allows the filter to perform correctly by protecting your heating/ac system. The filters don’t need to fit with an “air tight” seal, but you should be able to easily install and uninstall your filter without a struggle, plus the filter shouldn’t be so small that it moves freely within your unit. Your filter should be a bit smaller on each side of the filter housing slot, thus allowing you to slide the filter in with ease. Most AC and HVAC units use standard sized filters, but some do require a custom size air filter.

Some Signals that Your Air Filter is Too Small:

1. The air filter moves around too much inside the filter housing slot.
2. When your unit turns on, you hear noises such as knocking, whistling, or rattling.
3. Once installed, the air filter does not completely cover the vent or duct opening.
4. You notice that the air filter does not seem to get dirty.

Consequences of Using an Air Filter That is Too Small:

1. The filter can be sucked into the ventilation if it is much smaller than it should be.
2. Dust, allergens and pollutants will not be filtered from your indoor air, as the air is bypassing the filter and entering into the ventilation and is returned back.
2. The filter will be unable to protect your AC/HVAC unit and the unfiltered air will collect on internal components of your system, such as the coil and fan, which can lead to expensive repairs.

If you are questioning whether or not your filter is too small, here are a few suggestions on how to check:

Measure the air filter housing slot, but only the usable space where the filter can fit into. Make sure to take into consideration any overlaps or recessed edges that may obstruct installing or uninstalling the filter. For most systems you can use a standard sized filter within 5/8-in smaller than the air filter housing. If you are not able to find a standard sized filter within that parameter, you will need to order a custom sized air filter.

There are also air conditioning/HVAC units that are open-ended, meaning you don’t close a door or panel over the air filter housing. In these cases, you have more flexibility in selecting your filter size, as you can choose one that is longer than the size of the opening. This also gives you a pseudo “handle” that sticks outside the opening that allows you to grab onto for ease of removal when it’s time for the filter to be changed.

An excellent resource to help you is the US Environmental Protection Agency (EPA) Guide To Air Cleaners in The Home.

How to Choose Your Air Filter Size for Each Unit Type:

1. If your unit has wall and ceiling vents that do not have clips or brackets that secure the filter you want to find the closest fit possible (within 1/8-in. smaller than the opening) that prevents movement or noises as mentioned above.
2. If your unit has wall and ceiling vents that has clips or brackets that secure the filter you can select a filter size within a 1/2-in. smaller than the opening.
3. If your unit has a standard filter slot (typically located near the blower unit) you can select a filter size within 1/8-in – 5/8-in. smaller than the two longest sides. As mentioned above, you can also choose a longer filter as there is no door or cover that needs to be closed over the filter.
4. If your unit has a filter cabinet or drawer/large housing compartment you will need to select a specialty Whole House Air Filter (filter depth should be over 4 inches). Look  for the part number or model number on the door/panel/housing or the reference number on the air filter to find the actual filter size.

Order now from US Home Filter and receive FREE SHIPPING on your order!

Selecting the filters that are just right for your home can be difficult and confusing at times. At US Home Filter we understand this, which is why we offer an experienced staff to help answer any questions you may have. For personal assistance with your air filter needs, please contact us now online or call us at (855) 237-1673 and we will do our very best to assist you in selecting the right filter for your individual needs. We carry humidifier filters and pads for all major manufacturers (including Air King, American Standard, AprilaireGeneralAire and Honeywell). We want to earn your business and we guarantee your satisfaction! Take advantage of our quality products, vast selection, low prices, and enjoy FREE SHIPPING on every air filter order within the Contiguous USA.

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