Cannabis Air Filter for Smoke: HEPA and Carbon

Cannabis Air Filter for Smoke: Answer

Use a filter with two stages: a HEPA filter and activated carbon. HEPA captures smoke particles. Carbon captures odor and gases. A HEPA filter alone removes particles but leaves smell. A carbon filter alone leaves particles. Combine both.

read more

How Cannabis Smoke Moves

Smoke from cannabis contains particles from 0.1 to 1 micron. HEPA filters capture 99.97% of particles at 0.3 microns. That range covers most smoke. Smoke also carries volatile organic compounds (VOCs) and terpenes. Carbon adsorbs these compounds. The carbon weight matters. A filter with 2 pounds of carbon lasts longer than one with 4 ounces.

read more

Filter Specs That Matter

• True HEPA: meets HEPA standard, not "HEPA-like" or "HEPA-type".
• Carbon weight: measured in pounds or grams. More carbon equals more odor removal.
• Pre-filter: captures lint, dust, and large resin particles. Extends HEPA life.
• CFM rating: cubic feet per minute. Match to room volume.
• Air changes per hour (ACH): for smoke, aim for 4 to 6 ACH.

Size the Filter to the Room

Calculate room volume: length x width x height in feet. Example: 10 ft x 12 ft x 8 ft = 960 cubic feet. For 4 ACH, filter needs 960 x 4 / 60 = 64 CFM. For 6 ACH, 96 CFM. Add 20% for filter resistance. Choose a unit rated for at least that CFM.

related article

Placement and Maintenance

Place the filter near the smoke source. Do not block intake or exhaust. Run the filter during and after smoking. Replace pre-filters every 1 to 3 months. Replace HEPA every 6 to 12 months. Replace carbon every 3 to 6 months. Resin clogs filters faster in heavy use.

What to Avoid

Ozone generators produce ozone. Ozone irritates lungs. California bans ozone generators in occupied spaces. Ionizers may produce ozone as a byproduct. Avoid filters that use only ionization. Avoid "air purifiers" with no carbon. Avoid filters with no CFM rating.