Enter the real room dimensions, ceiling height and target air changes. Tecnobosque calculates the smoke CADR your room needs and how many purifiers are required to meet that clean-air target.
Results update as the room or target cleaning rate changes.
CLEANER × 1
What size air purifier do I need for wildfire smoke?
For a chosen target air-change rate, multiply the room volume by that rate. Keep the volume and delivery units consistent:
- CADR in cfm = room volume in ft³ × target ACH ÷ 60.
- CADR in m³/h = room volume in m³ × target ACH.
ACH means air changes per hour. For an 8-foot ceiling, EPA’s smoke-CADR rule of at least two-thirds of room area is equivalent to about 5 ACH. EPA guidance also cites the stronger wildfire-smoke sizing approach of a smoke CADR approximately equal to room area, equivalent to about 7.5 ACH when scaled by room volume. These are planning targets, not guarantees of safe exposure.
Example: a 300-square-foot room
With an 8-foot ceiling, volume is 300 × 8 = 2,400 ft³. At the selected 5 ACH, required clean-air delivery is 2,400 × 5 ÷ 60 = 200 cfm. Raising the ceiling to 10 feet, with the same floor area and target, changes the calculated requirement to 250 cfm.
Example: a 20-square-metre room
With a 2.5 m ceiling, volume is 20 × 2.5 = 50 m³. At 5 ACH, calculated clean-air delivery is 50 × 5 = 250 m³/h. There is no division by 60 here because the output is already per hour.
Is the product’s advertised room area enough?
Check the ceiling height, air-change assumptions and smoke CADR behind the coverage claim. EPA advises sizing for the served space, accounting for higher ceilings and open layouts. It also notes that CADR is usually measured at the highest fan speed. Read EPA’s guide to air cleaners.
CADR describes particle cleaning, not removal of every gas or pollutant. Actual results also depend on leakage, filter condition and operation.
Use published smoke CADR, power and noise. Model indoor PM2.5 →
Add infiltration, CADR and room volume. Size backup battery →
Estimate purifier runtime during an outage.
From required smoke CADR to backup battery
The room requirement comes first. Choose a purifier configuration that meets the calculated CADR, confirm its electrical load, then size battery capacity for the outage duration you want to cover.
Power-station examples screened against this requirement
These are two affiliate-linked examples already available through Tecnobosque, not a whole-market ranking. Technical pass/fail is calculated from capacity and continuous AC output.
Open the full purifier specification comparison → · Open the full battery-runtime model →
Keep the purifier running during a power outage
Once you have sized the clean-air delivery, check the electrical load at the fan setting you intend to use. CADR and watts describe different things: a longer battery runtime does not establish adequate filtration.
How long can a power station run an air purifier? Work through 12-hour and 24-hour battery sizing, runtime tables and a purifier-plus-router example.
Clean Air Delivery Rate represents the volume of filtered air delivered over time. A larger room or a higher target air-change rate requires more clean-air delivery.
When a manufacturer provides separate CADR values for smoke, dust and pollen, use the smoke CADR for wildfire-smoke particle planning.
The tool divides the calculated clean-air requirement by the smoke CADR entered for one purifier and rounds upward to the next whole unit. It also shows the resulting theoretical ACH from that number of purifiers.