4 ms·

The University of Michigan made an instructional video showing how you can easily make an air purifier out of a box fan and a HEPA-rated furnace filter for $25:

by Qub3d 6y ago

The University of Michigan made an instructional video showing how you can easily make an air purifier out of a box fan and a HEPA-rated furnace filter for $25: https://www.youtube.com/watch?v=kH5APw_SLUU https://www.youtube.com/watch?v=kH5APw_SLUU It won't be as good as a purpose-built machine, but it will be far better than nothing at all. TheWirecutter found it reduced particulate matter in a room by 87%, if you do it right. They also make clear important caveats about this method -- in short, this works in a pinch, but probably should not be used in place of a purpose-built filter if you want one for year-round use. https://www.nytimes.com/wirecutter/reviews/best-air-purifier/#what-if-you-just-put-a-furnace-filter-on-a-box-fan https://www.nytimes.com/wirecutter/reviews/best-air-purifier...

ALittleLight 6y ago
I have two of these running right now. According to my air quality meter, PM 2.5 has fallen from about ~250 indoors to ~40. (My meter shows ~600 outside, which is about 3x what the government website shows for my area)
- meristem 6y ago
  Government website most likely using an algorithm that pools data and takes into consideration multiple readings, sometimes lagging by a few hours. Your sensor gives the instant value in your immediate environment (assuming it is well-calibrated and installed outside of local influences such as kitchen fans, dryer lint etc etc)
- koolba 6y ago
  What do you use to measure air quality?
  - ALittleLight 6y ago
    I use this thing: https://www.amazon.com/gp/aw/d/B0787Z5DK9 https://www.amazon.com/gp/aw/d/B0787Z5DK9 I'm not sure how accurate it is or isn't. It reacts to the filters, for example, or if I hold it in front of the filter it'll reach a very low number, conversely if I take it to other parts of the house or outside it'll increase. I've done a few trials like that and it seems directionally accurate, but I can't speak to the numerical accuracy. It measures PM 2.5 and 10 and has a button to show graphs over time for ~12 hours. Battery life is pretty good, I usually leave it detecting on the charger, but I've had it in handheld mode for several hours and stayed above 80%. It's super simple to use. One thing I don't like about it is that it has a cheap plastic hinge that is supposed to let it stand up, but it broke on me after a couple uses. It doesn't seem to matter though if it's standing up or laying down, it still reads pretty much the same. I wish it had a way to export data to my computer or maybe an app.
blendo 6y ago
Even easier: just place the 20”x20” filter BEHIND the box fan. The vacuum will keep it in place nicely. Be sure to note the airflow direction arrows on the filter.
- y-c-o-m-b 6y ago
  I put it behind the fan as well, but now I'm curious if there a difference in air quality between the two methods?
  - netcraft 6y ago
    if the filter is the same distance from the fan, there really isn't much of a difference. Filter after the fan is perhaps a bit better from a turbulence and noise perspective. https://www.quora.com/Where-should-an-air-filter-be-placed-relative-to-the-fan-for-best-efficiency https://www.quora.com/Where-should-an-air-filter-be-placed-r... One thing to keep in mind though is most filters have an expected direction of airflow, which does matter both to its efficacy and efficiency.
    - shard 6y ago
      I put the filter behind the fan, the reason being that the filter will be sucked onto the fan, thus providing a better seal between the fan and filter than it would be if the filter was in the front and being actively pushed away from the fan by the air.
  - proee 6y ago
    Putting the filter behind the fan ensures you have clean air contacting the fan blades. This prevents contaminants from accumulating on the fan blades over time and reduces cleaning.
UncleOxidant 6y ago
Portland burbs here: box fans and filters of all types sold out days ago. A lot of people here doing the box fan filter.

by Qub3d 6y ago

ALittleLight 6y ago

I have two of these running right now. According to my air quality meter, PM 2.5 has fallen from about ~250 indoors to ~40. (My meter shows ~600 outside, which is about 3x what the government website shows for my area)

meristem 6y ago
Government website most likely using an algorithm that pools data and takes into consideration multiple readings, sometimes lagging by a few hours. Your sensor gives the instant value in your immediate environment (assuming it is well-calibrated and installed outside of local influences such as kitchen fans, dryer lint etc etc)
koolba 6y ago
What do you use to measure air quality?
- ALittleLight 6y ago
  I use this thing: https://www.amazon.com/gp/aw/d/B0787Z5DK9 https://www.amazon.com/gp/aw/d/B0787Z5DK9 I'm not sure how accurate it is or isn't. It reacts to the filters, for example, or if I hold it in front of the filter it'll reach a very low number, conversely if I take it to other parts of the house or outside it'll increase. I've done a few trials like that and it seems directionally accurate, but I can't speak to the numerical accuracy. It measures PM 2.5 and 10 and has a button to show graphs over time for ~12 hours. Battery life is pretty good, I usually leave it detecting on the charger, but I've had it in handheld mode for several hours and stayed above 80%. It's super simple to use. One thing I don't like about it is that it has a cheap plastic hinge that is supposed to let it stand up, but it broke on me after a couple uses. It doesn't seem to matter though if it's standing up or laying down, it still reads pretty much the same. I wish it had a way to export data to my computer or maybe an app.

blendo 6y ago

Even easier: just place the 20”x20” filter BEHIND the box fan. The vacuum will keep it in place nicely. Be sure to note the airflow direction arrows on the filter.

y-c-o-m-b 6y ago
I put it behind the fan as well, but now I'm curious if there a difference in air quality between the two methods?
- netcraft 6y ago
  if the filter is the same distance from the fan, there really isn't much of a difference. Filter after the fan is perhaps a bit better from a turbulence and noise perspective. https://www.quora.com/Where-should-an-air-filter-be-placed-relative-to-the-fan-for-best-efficiency https://www.quora.com/Where-should-an-air-filter-be-placed-r... One thing to keep in mind though is most filters have an expected direction of airflow, which does matter both to its efficacy and efficiency.
  - shard 6y ago
    I put the filter behind the fan, the reason being that the filter will be sucked onto the fan, thus providing a better seal between the fan and filter than it would be if the filter was in the front and being actively pushed away from the fan by the air.
- proee 6y ago
  Putting the filter behind the fan ensures you have clean air contacting the fan blades. This prevents contaminants from accumulating on the fan blades over time and reduces cleaning.

UncleOxidant 6y ago

Portland burbs here: box fans and filters of all types sold out days ago. A lot of people here doing the box fan filter.