Rigid Cell Box Filters

Rigid Cell Box Filters

A rigid box style filter is often used as secondary air filter or as the final filter, in an air system. Often referred to as a box filter, these filters are designed to work best in Variable Air Volume (VAV) systems, where air speed volumes can change.

Box filters can be used to replace pocket bag filters, however a bag filter should not necessarily be used to replace a box filter.

Box filters are available in 65, 85 and 95% efficiencies, or MERV 11, 13 and 15 ratings. Box filters are usually paired with less efficient cardboard pleats, typically a MERV 8.

A standard size 24x24x12 box filter can have up to 58 square feet of media, within that frame. For comparison, a high capacity 24x24x2 cardboard frame pleat, has about 18 square feet of media. Generally, a larger surface area will give you better Dust Holding Capacity (DHC) and longer service life of the filter.

Pairing a lower rated pre-filter pleat, such as a MERV 8 with a higher efficient MERV 13 box filter, for example, will help extend the service life of the rigid box style filter.

Changing the pre-filter pleats 3 or 4 times a year, may extend the life of the secondary filter up to a full year, depending on the application.

Box style filters are very versatile in their application because they have few restrictions. Box filters can be used in constant air volumes (same as bag filters). But box filters are increasing in presence because of the increasing VAV motors we see more of today.

Energy consumption and awareness are a big part of modern buildings budgets. Operators realize the costs involved, pushing conditioned air through a system, and the flows of volume vary depending on conditions.

Some operators slow down air speeds on weekends or even overnight. These buildings use VAV to save energy costs and box style filters are designed best for these applications. For these reasons, some applications of a box filter might include a large modern building, shopping malls, theatres and sporting venues.

The box, or rigid style is always “open” with, or without air passing through. Unlike bag filters, no off loading or damage can occur to a box filter.

Once you decide which secondary filter you need, bag or box style, you will need to choose an efficiency. Our box filters are offered in MERV 11, 13 and 15 to accommodate almost every application you may require.

These box style filters are offered with or without a header on the filter frame.

United Filter can assist in helping you decide what is best for your application.


  • 24 gauge galvanized steel frame with reinforced corners
  • synthetic double density media laminated to an expanded wire 95% open
  • used in side or front access housing for 2nd stage filtration
  • standard and custom sizes in 6" and 12" depths (with or without header)
  • commercial and industrial applications.
  • variable air volume units
  • medium to high efficiency


  • 60-65% MERV 11
  • 80-85% MERV 13
  • 90-95% MERV 15

Let us know what your requirements are and we will get back to you within one business day with pricing and delivery.