We rate our filters at “one event.” If you have nuclear, biological, and chemical event in your neighborhood and you turn on your Safe Cell, you need to change the filters as soon as you get the all clear.
The particulate filters (the pre-filters and the HEPA filter) actually filter more effectively as they load up. We’ve tested our filters with 14 pounds of smoke particulates and they had almost no effect on the airflow.
To ensure the particulate filters last as long as possible, we designed the bottom end bell to have the proper standoff depth so the airflow is diffused and hits the particulate filters over their entire surface. The airflow needs distance to slow down and spread out as it goes from the 4 inch round intake port (12 square inches) to the 12 inch square HEPA filter (144 square inches).
The carbon adsorber attracts and traps gases, molecule by molecule onto the surface of the carbon. Water vapor is one of the gases the carbon adsorbs. Because of this, we recommend keeping the Safe Cell sealed with the shipping caps when not in use so that the performance of the carbon is not degraded by adsorbing water vapor from the atmosphere.
If not used and kept in the original packaging in a climate controlled environment, we recommend replacing the HEPA after six years and the carbon adsorber after three years. See our replacement filter page for more information.
One more note on replacement filters: after the nuclear incident in Japan in 2011, we were sold out of filters within a couple of days. If there is a nuclear event anywhere in the world, we will probably be back ordered on Safe Cells and replacement filters. Every Safe Cell installation should have a complete set of replacement filters.