The Accordion paint baffle captures particulates on the back wall of the pocket. As the pocket fills, air velocity increases and particulates are captured at a greater rate (efficiency increases with increased static pressure). The Accordion can withstand pressure drop greater than 1 inch w.c.
When using The Accordion, the fan capability is the limiting factor in determining how long the filter will last. If the fan motor is capable of moving air at a high rate of static pressure, then the filter will last until 100% efficiency is achieved (at which point, of course, the filter is 100% loaded and airflow has ceased). Per OSHA regulations, “the average air velocity over the open face of the booth (or booth cross section during spraying operations) shall be not less than 100 linear feet per minute.”
To achieve the absolute longest filter life, change your filters at the point just before the fan unloads. Using a manometer or magnehelic gauge, mark the meter when clean filters are installed and the blower is on. Then use cardboard to cover the filters and mark the meter again when the fan unloads. This is the maximum increase in pressure your fan motor can handle. Change your filters when the pressure approaches the upper mark.
Older fans may only be able to achieve 0.5 inch w.c. but new fans are typically equipped with motors than can achieve an increase in pressure that is greater than 1 inch w.c.