undefined

points

[-]

You don't need to seperate the clean and dirty air. Mixing them isn't as efficient but it should still be roughly 63% efficient (1-1/e).

by hxtk17 minutes ago|

parent|

[-]

The point isn’t that the HEPA filter won’t work under those conditions, it’s that if you can get away with not separating the clean and dirty air, you can achieve better filtration overall with a higher flow, lower resistance filter at a lower noise level. HEPA filters shine in use cases where you need single-pass filtration, like vacuum cleaner output filters or clean room air filters. If you don’t separate clean and dirty air, the filter will still work, but you aren’t taking advantage of its main distinguishing quality, which is its single-pass filtration performance.

If you get to recycle the air through the filter several times, MERV-13 offers much better performance tradeoffs for a residential air purifier because you can recycle the air through it much faster at acceptable noise levels. My home air purifier recycles the volume of my home every 15 minutes or so, vs HEPA filters which produce totally clean air, but since it just mixes with the dirty air that doesn’t matter as much as the rate at which it cleans air.

by enquirewithin4 hours ago|

prev|

[-]

A reasonable compromise is achieved by an air purifier that has the outlet on top because it’s blowing the filtered air well away from the inlet side and generally circulates the air in the room.

I used to work in the cleanest room in the state, that wasn’t a lab, back when I lived in Adelaide, and top-inlet button-outlet in a raised floor data centre is how the air handling units in the main data hall worked, so you can simulate that to a certain extent.

> The more effective the filter the more it restricts airflow.

This isn’t the whole story. Surface area and flow rate are factors.

A residential home is aiming to improve air quality, rather than grow flawless silicon ingots etc.

by victorbjorklund3 hours ago|

prev|

[-]

What you wanna say is it might be more efficient with more CADR per minute with less filtration than less CADR an a higher filtration.

But a HEPA filter is better than no filter. Even if would be more effective with another.

(Also depends on size of hepa filter and room to clean. Large enough filter and small enough space and Hepa can clean all the air)

by adrianN5 hours ago|

prev|

[-]

Any air purifier should be able to cycle the air in a normal room often enough that it should be quite clean in a short time.

by tallanvor5 hours ago|

prev|

[-]

If the purifier can filter the air more quickly than air leaves the room it'll still reduce the amount of pollutants in the air. Most people aren't going to create a "clean side" and "dirty side" setup for filtering the air in a room.

by rcxdude4 hours ago|

parent|

[-]

I think that is what they're saying: the point is that if you're doing this, you don't want to optimize for the cleanest air leaving the filter, but more for throughput.

by OroPla1 hours ago|

prev|

[-]

If you only use 99% it means there are small particles you can't catch. Being faster is meaningless if you can never clean the air.

Air purifiers are designed to run 24/7 and all they do is catch particles. Eventually all the particles will be caught. The one I got also detects if there is a lot of particles and will spin faster accordingly.

by mrob1 hours ago|

parent|

[-]

>If you only use 99% it means there are small particles you can't catch.

Air filters don't work like sieves. The smallest particles are easier to block than the mid-sized particles. See:

https://en.wikipedia.org/wiki/Mechanical_filter_(respirator)

Clean Air Delivery Rate is often specified for specific pollutants. One is smoke, which is mostly small particles.