What is activated carbon?
HEPA filters are designed to capture particles like the small PM 2.5 particles. Activated carbon, though, captures odors and gases like volatile organic compounds (VOCs). VOC is a big category and includes harmful carcinogens like formaldehyde and benzene.
Does activated carbon really work?
To answer this question, we ran tests with an Industrial Scientific MX6 iBrid gas detector that can detect VOCs and a host of harmful gases. In an enclosed 4.14m2 porch, we lit three cigarettes (known to emit formaldehyde and benzene), turned on a Cannon fan with a carbon filter, and tracked VOC concentration. We also ran a control test of a fan with no carbon attached. The results (left) showed the carbon layer effectively reduced VOC concentrations.
Does everyone need a carbon filter?
Not necessarily. Not all homes have dangerous levels of harmful gases or VOCs that would call for a carbon filter. VOCs are more common in homes:
- with recent home renovation or repainting
- with smoke or other offensive odors
- near a source of gas pollution like a factory
If you have inflammation or asthma symptoms, you may also consider using a carbon filter.
Do I still need a HEPA and a Carbon?
Yes. Activated carbon is not very effective at filtering particulate pollution, the primary pollutant affecting cities in China. For that, a HEPA is still the best choice.
How do I install a carbon filter?
If you use a Cannon, you can install an activated carbon filter and a HEPA filter simultaneously. On the fan opening, first place the carbon filter then place the HEPA on top (as shown in the Filter Order diagram to the right). On our Original DIYs, we suggest not using a carbon and HEPA simultaneously. If VOCs are a problem you can use just a carbon on our Original DIY though!
Cannon users can install activated carbon and HEPA layers simultaneously using the stacking order shown above.