You can increase the filtering efficiency of the Razaire MINI by adding one or more Primary Filter Expansion Kits. Each kit includes an Expansion Frame and a new Primary Filter. No tools required. To install simply remove the Top Cap from the unit and snap in the Expansion Frame. The extra filter can be set directly on top of the existing filter (be sure to remove the protective paper tabs from the new filter first). Snap the top cap back in place.
You can add as many extra Primary Filter stages as you want, however air flow through the unit will be reduced slightly with each additional filter stage you add.