Buy a two-part setup instead of one miracle device: a sealed air purifier that pairs true HEPA filtration for smoke particles with several pounds of activated carbon for odor, plus a ventilation path that moves air out of the room. Recirculation alone clears haze, but without exhaust the smell migrates through doorways and shared HVAC. Size the purifier to turn the room over four to six times per hour, keep the carbon stage fresh, and reject any unit that produces ozone. That combination is what actually answers how to filter cannabis smoke indoors without wrecking the rest of the house.
CADR: aim for a smoke CADR at least two thirds of the room's floor area in square feet for fast clearing, or equal to the area for heavy daily smoking. Carbon: 5 to 15 pounds of activated carbon for a room used several times a day, replaced every three to six months under heavy load. Air changes: four to six per hour for smoke, which you can estimate by dividing total CFM by room volume in cubic feet and multiplying by 60. HEPA replacement: six to twelve months in a smoke-heavy room. HVAC: a MERV 13 filter or better if your system can handle the pressure drop. Exhaust: enough CFM to swap the room's air once or twice per hour while smoking.
It removes the particles that carry much of the odor, but the volatile compounds need carbon. A HEPA-only unit reduces haze and leaves a lingering scent.
With a properly sized unit, visible haze drops in about 20 to 30 minutes. Odor takes longer and depends on soft surfaces in the room.
Yes. Exhaust stops smoke from spreading to other rooms. The purifier cleans what stays behind.
No. Regulators treat ozone as a lung irritant and advise against devices that generate it in occupied spaces.
Rinse the pre-filter monthly, replace HEPA every six to twelve months and carbon every three to six months in a room used daily.