The 91-008 is the 15 inch x 15 inch x 2 inch replacement MERV 11 pre-filter for the Ultravation HEPA Whole House Air Cleaner model 93-001. The 91-008 is also the replacement pre-filter for the Ultravation Photronic Multistage Air Cleaner with true HEPA filtration models: 92-016, 92-017, 92-018 and 92-022.

The 91-008 replacement pre-filter uses Ultravation Progressive Media Filtration with Ultrastrand fiber technology, which meets and exceeds MERV 11 (ASHRAE 52.2) performance standards. Ultravation MERV 11 filters can capture particles as small as .3 microns in size. The specially shaped surface of an Ultrastrand fiber captures and holds particles far better than the typical round fiber.To increase capture ability still further, Ultrastrand fibers carry a permanent electrostatic charge that attracts particles like a magnet.

Ultravation Progressive Media design increases fiber density from the upstream to downstream side, gathering the largest particles in the first part of the filter, while progressively smaller particles are captured through the filter. As a result, the media becomes filled edge to edge, providing very high dirt holding capacity.

The manufacturer recommends you change the pre-filter every 6 months under normal operating conditions.