Activated Charcoal Standard 30% Efficient (gray) filter.
Most often used as a second stage to reduce many odours like burning wood, antler and eggshell. Recommended as a second stage as it will require frequent replacement if used alone. Note: This filter does not eliminate odours. It has proven effective in reducing airborne odours and works best at low fan speed settings.
About Razaire filters. There are 4 different filters available for the Razaire. While they work fine as single stage filters, they are best used in pairs (stacked). Adding an extra filter stage increases both the performance and the life of the filter, with little to no discernible drop in suction. All filters are approximately 9.75" x 10.5" x 2".