21x21x1 MERV 13 AC & Furnace Filters (6 Pack)

MERV stands for Minimum Efficiency Reporting Values and is an industry-created standard that evaluates the efficiency of air filters. The MERV rating of any particular air filter ranges on a scale of 1 to 16, with a filter rating 1 being the least efficient and a filter rating 16 being the most efficient.

However, it is not always as simple as buying a filter with the highest MERV rating. Highly-rated MERV filters have very small pores, which creates more resistance against air flow that may put too much pressure on the fan in your unit.

We recommend a MERV rating between 8 and 11 for most residential furnace and AC units to adequately remove airborne contaminants. Filters with a higher MERV rating must be replaced at least every three months to avoid restricted air flow and negative effects on your furnace’s performance.

How often should I change my filter?

Actual replacement times will depend on a variety of household conditions, including running time on the furnace or air conditioning unit, the type of flooring in the house, and the presence of kids and/or pets. Generally, air filters should be replaced about every 2-3 months for optimal performance.

How do I find the dimensions of my air filter?

Air filters use two sets of dimensions: actual and nominal. The actual dimensions are the exact height, length, and width measurements. Most filters are sold under nominal dimensions, which are rounded off to the nearest 1" measurement. For example, if your air filter measures 10 ½“ x 20 ¾” x 1¼”, the nominal dimensions will typically be 11” x 21“ x 1”. To find your filter size, we recommend measuring the actual dimensions of your existing filter and choosing the closest match in nominal dimensions.

Filters should fit snugly without having to be forced into place. Forcing in a filter that is too large can cause tearing or buckling and results in a loss of efficiency. If you notice air leakage around the sides after installation, you may use gasket tape around the edges of the filter to create a tighter fit.

What is the benefit of using a carbon air filter?

The Odor Eliminator filter uses a carbon filter media to efficiently remove household odors without reducing air flow. Carbon media granules create more outer surface area for odors, fumes, and other contaminants to adhere to, and are resistant to moisture and microbial growth. The filter fits into existing filter housings to provide efficient, guaranteed odor control at a price that competes with standard pleated air filters!