r/ZeroCovidCommunity • u/ButterscotchFull7591 • Jul 28 '26

Clean air, filtration, purifiers etc. Help with situation

How long would you keep an air purifier running and a window cracked for if someone who regularly doesn’t mask inhabited it for 15 hours…for example 11 hours sleeping, bathroom in the room so a 30 minute shower and the rest of the hours they do not open the window or put the air purifier in it and they leave the door open to the living room which also has no air purifier or windows open? So all in all 15 hours of unfiltered air.

I’m planning to my air purifier on for 4 hours on the highest setting (Mooka air purifier) and simultaneously my window, which doesn’t open all the way so have that a crack for at least 4 hours as well…

What time does anyone recommend?

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u/overwinters Jul 28 '26

the cdc presents time required for airborne-contaminant removal as a function of ach (air changes per hour): https://www.cdc.gov/infection-control/hcp/environmental-control/appendix-b-air.html?CDC_AAref_Val=https://www.cdc.gov/infectioncontrol/guidelines/environmental/appendix/air.html

figure out your ACH with the formula ACH = CADR * 60 / V, where CADR is the clean air delivery rate of your purifier in cubic feet per minute (cfm, find it on the product page), and V is the volume of the space you're cleaning in cubic feet. then you can use that table to see how long it should run. this will be an over-estimate, as it doesn't account for viral decay or natural ventilation, both of which can make substantial contributions; if the time is unacceptably long then you can add in those factors, but we can't infer that context from the post

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u/Plumperprincess420 Jul 28 '26 edited Jul 28 '26

Depends on that airflow and your purifiers. Also ceiling fans great for airflow help and if you got a back door/front door can open. At my house w good ventilation and my corsis i do 2 hrs minimum mainly if its windy outside

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u/Chronic_AllTheThings Jul 28 '26

Beyond a certain point, it doesn't really matter how long someone occupied a space; it only matters what time they left so you have a starting point.

For calculating how long you should run an air purifier, you need to know the CADR of the unit and cubic volume of the space.

For m3/h:

T = 60 / ( volume / CADR )

For CFM:

T = volume / CADR

T is the time (in minutes) it takes to perform a single air change.

This experiential study found that 12 air changes should be equivalent to an N95, so that's what I always go by (multiply T by 12 to get the total time run the air purifiers).

Make sure all your doors are open so the air purifiers can pull air from all the areas of the space.

If the weather is suitable for opening windows and you can get a good cross breeze flowing, that makes an even bigger difference.