CADR CALCULATOR

Usual disclaimers apply, such as clean air can't stop all near field transmission, efficacy of clean air depends on the number of infected people in a space and the amount of virus they are exhaling. A N95 or equivalent mask is the most cost effective and efficient way to prevent near field and far field transmission. Instructions on how to make your own sensor...https://docs.google.com/document/d/1VqQmpKjpsU_dGP52nNLSMSJ8Jj1FbcuBaTjk00IvkBM/edit?usp=sharing

Choose your venue. (Base outside air delivery rate in Liters Per Second (LPS))*

Choose an activity. (CO2 generation rate)*

Classroom of children under 12 (0.00385)Sitting - movie theater, lecture hall (0.004)Using a computer, eating, mostly sitting(0.00552)Moving around normal pace - shopping (0.00736)Low exertion quiet exercise - yoga (0.007)Moderate exertion exercise (0.001398)Maximal exertion exercise (0.0019)

Rank the vocalizations. (Factor score) This is basically a guess at how much to increase the ventilation/filtration to account for increased aerosols with talking.*

Normal talking for space (1)Singing, laughing, talking loudly such as a loud bar, concert with people singing along, group singing such as with a choir (2)

HOW MANY PEOPLE?*

ROOM CO2 IN PPM*

Measured Outside CO2 - or type in 400 if not measured*

Outside Air Delivery Rate per Person in LPS

Based on CO2 readings and the chosen activity level, and amount of outside air being supplied to the room, in liters/person/second.

The Goal

Recommended Outside Air Delivery Rate Equivalent based on Venue and Vocalizations in liters/second/person

The difference between the goal and what is delivered in Liters per Second per Person

The Number You Care About - total Clean Air Delivery Rate that your HEPA/CR boxes should deliver - LPS

CADR required in LPS

The Number You Care About if You Don't Like Metric Units - total Clean Air Delivery Rate that your HEPA/CR boxes should deliver - CFM

CADR required in Cubic Feet per Minute (CFM). LPS = CFM* 0.471

Step One - Look up your HEPA unit's CADR

https://docs.google.com/spreadsheets/d/17j6FZwvqHRFkGoH5996u5JdR7tk4_7fNuTxAK7kc4Fk/edit?usp=sharing. Be sure to pick your country at the bottom of the sheet. Thanks to CleanAirStars for creating this spreadsheet. The spreadsheet lists CADR in Metric, (LPS, Cubic meters/hour (M3/hr)) and in CFM, cubic feet per minute. It also provide information about energy use and filter replacement costs.

Step Two - Math

If the CADR of your HEPA is greater than the required CADR, you are good. Always run it at as high of level as you can tolerate sound wise since air mixing is important. If the CADR of your HEPA unit is less than the required CADR, you need additional units. If you are planning a gathering in your home, you might want to make a Corsi Rosenthal box. Large, very effective cheap filters can be made with a less than 10 year old box fan and 4 MERV 13 furnace filters and can be disassembled for storage. Smaller units can be made with Black and Decker 9 inch fans and 12 inch Merv 13 filters. Super quiet filters can be made with Arctic P14 computer fans. Putting filters up higher is better since exhaled breath is usually warmer than ambient air and keeps them out of the reach of children. More filters are better than few since they provide better air mixing in the room and when run at a lower speed, are quieter.

If the weather outside is tolerable, opening two windows will decrease CO2. A fan blowing out one window will increase air flow.

Calculator

Pick your HEPA's CADR L/S = CFM* 0.471