Comments on: DIY Box Fan Air Cleaner Update

By: Deniz Erkan

Deniz Erkan — Tue, 24 Jan 2023 04:48:51 +0000

In reply to Terry.

Terry, I thought merv 13 captures >75% at .3 microns. Anyway, there are posts in this blog describing how filters actually work with smaller particles.

Here is an article from another site
https://smartairfilters.com/en/blog/what-is-pm0-3-why-important/

By: leslie

leslie — Tue, 24 Jan 2023 02:01:51 +0000

how often do you run it? all day or just a few hours? can you leave it in a room when it isnt occupied? i dont want to hear the fan when i’m in the living room.

By: Terry

Terry — Thu, 12 Jan 2023 21:28:39 +0000

Let us start with some basic math. 1 micron is 1000 nm. therefore .3 microns is 300 nm. The covid 19 virus is approximately 100 nm. A Merv 13 filter at best captures .3 microns and then only 50%. A study out of South Korea states that in to kill this virus with UV-C at 99% it needs a 30 seconds of exposure. and is linear in its kill rate. So the virus passing thru this box would be exposed to the UV-C at best 1 to 3 seconds and the likelihood of it being trapped by the filter and thus having the requisite exposure time is negligible. The anthology that often given is stopping a mosquito with a chain-link fence. In this case it must stop the mosquito for 30 seconds in order for our UV-C to kill it.

By: Andy

Andy — Thu, 03 Nov 2022 13:54:24 +0000

We have air heating in this house, so I got some HEPA/virus particle size grade HVAC filters and stuck them over the air intakes at the start of Covid to purify the air. But it costs money to run the electric fan and/or gas heating to suck air through those filters. A much cheaper/free solution can be to open one window each side of the house/room to create and airflow. You can unblock your chimney/open the log burner door to create a chimney effect of rising air if you have one. Changing the air is just as effective as purifying it (so long as the source of the pollution isn’t coming in from outside your house!) and it’s ‘free’. Of course it might not be free if it’s freezing cold outside and then you have to pay to heat your house more, or if the day is completely windless and you can’t get a breeze. With either method, powered or a through-wind/draft, you can still catch an airborne virus or pollution, but your’e less likely to and you’ll receive a lower dosage, or viral load.

By: John Weil

John Weil — Tue, 06 Sep 2022 18:34:06 +0000

Using the piece of paper test, I also found reverse air flow around the central disk in the front of the fan screen. Has anyone else found this with whatever brand of fan they’re using? It might have been due to running at medium speed with just one filter, my last one.

By: MY

MY — Mon, 28 Mar 2022 01:18:27 +0000

Thomas: could we please just stop with suggesting that millions of people just ‘throw away’ perfectly good fan units?

It’s bad enough we have been creating all this garbage with disposable PPE/filters/containers/medical supplies without adding further to the problem. A LOT of those products could be reused if someone would just sit them in a corner for a few days.

By: Allison Bailes

Allison Bailes — Wed, 16 Feb 2022 00:55:05 +0000

In reply to Russ Pagulayan. Russ: Yes, it will work either way you blow the air. By blowing the air into the box, though, you create more turbulence, which lowers the air flow rate and clean air delivery rate. It's also noisier. We've got one of each in our office.

By: Russ Pagulayan

Russ Pagulayan — Wed, 16 Feb 2022 00:25:04 +0000

With the fan blowing out from the filter, all of the particles will be trapped on the outside of the filter box. Could it work better if the fan blew into the box, thereby all of the particles would be contained inside the filter box?

By: Gary Atcheson

Gary Atcheson — Mon, 17 Jan 2022 04:43:36 +0000

In reply to RoyC. I agree it would be better to see it higher for trapping the virus. Sitting on the ground may help general IAQ by picking up dirt tracked by shoes, but feels less effective for the virus circulating up around our airways.

By: Allison Bailes

Allison Bailes — Mon, 10 Jan 2022 22:39:26 +0000

In reply to Rosscoe. Rosscoe: It depends on how much you use it, and how dirty the air is. One way to make the call would be to measure the initial pressure drop across the filters and change them when the pressure drop doubles. Another would be to change them when they're too dirty to look at anymore.