8 ms·

Heres my set up: - 20 inch box fan - 20x20x4 MERV12 filter. The 4-inch pleating is key here, to reduce the air resistance on the box fan. - 1 inch dust pre-f

by DeRock 5y ago

Heres my set up: - 20 inch box fan - 20x20x4 MERV12 filter. The 4-inch pleating is key here, to reduce the air resistance on the box fan. - 1 inch dust pre-filter. This is course, low air resistance, and is for increasing the life of the more expensive MERV12/HEPA filter (so it doesn't get clogged with easy to filter dust). - Both filters are on the intake side of the box fan. This means you don't need a bungee cord because the intake has negative pressure, the filters just "stick". It also means you keep your box fan flowing with only cleaned air. Heres a pic of my setup: https://imgur.com/a/O4I6Udx https://imgur.com/a/O4I6Udx And here's a graph this morning from my air quality sensor, after turning on the fan/filter: https://imgur.com/a/c5GMNcC https://imgur.com/a/c5GMNcC The peak at ~30ug/m^3 PM2.5 is approximately 100 AQI. The fan was on the other side of my 900 sqft house from the sensor.

chana_masala 5y ago
Thanks for sharing, that's neat how simple it is. What air quality sensor setup do you have?
- DeRock 5y ago
  HM3301: https://wiki.seeedstudio.com/Grove-Laser_PM2.5_Sensor-HM3301/ https://wiki.seeedstudio.com/Grove-Laser_PM2.5_Sensor-HM3301... Attached over I2C to an ESP32 running ESPHome: https://esphome.io/#air-quality https://esphome.io/#air-quality Which in turn reports to a raspberry pi running Home Assistant: https://www.home-assistant.io/installation/ https://www.home-assistant.io/installation/ Took about 20 mins to set everything up.
  - jve 5y ago
    > Took about 20 mins to set everything up. Given you have Home Assistant installed and have previously used ESPHome. And attached wires. Otherwise, you may be up to a journey that takes many hours/days. That's the difference experience makes :)
    - DeRock 5y ago
      The only thing set up was the raspberry pi having an OS installed. Had never used HA or ESPHome before. I was shocked how easy it was if you're comfortable with a terminal. I'd never even used docker before. My steps were: 1. Install docker 2. Install/run HA through docker 3. Install/run ESPHome through docker (there's a config wizard) 4. Edit the ESPHome .yaml from (3) to my preferences 5. Connect 4 wires from the ESP32 to the air quality sensor 6. Plug ESP32 USB to RPi 7. Run docker esphome on the above yaml. This compiles, flashes, and boots your ESP32, auto-connecting to your network 8. Add the ESP air quality sensor to HA through the web GUI
      - jve 5y ago
        That's (almost) exactly what I did and without prior docker experience. I must admin it was less hassle with docker, but still docs for particular containers had to be read to understand configuration options. + setting up for external access, letsencrypt and tying that everything within docker-compose. I didn't manage to do it in 20minutes, but more like full working day maybe? Anyway, HA is recommended. Haven't tried ESPHome, but Tasmota is an alternative that also does the job, if you someone ever wants to research the options.
    - jrockway 5y ago
      Turnkey microcontroller projects can be really quick. Adafruit and Sparkfun sell many of their breakout boards with special cables for I2C now, so you might not even have to solder anything. From there, you can drag a Python script to the microcontroller (which appears on your PC as a flash drive). Building enclosures for these projects used to be an annoyance, but everyone provides CAD models of their stuff now, so you just kind of lay it out in your CAD program, extrude a box around it, and print it out. Never been a better time than now to be building sensors and that sort of thing. (Even with the STM32 shortage!) As for the Raspberry Pi -- my rule is to treat embedded systems like hardware. Download a Linux image with the software you want on it, copy it to an SD card, plug that in, and go. I use this model for Octopi and while I might have changed the password and uploaded a profile for my printer file, that's it. If the RPI blows itself up, $35 and 5 minute fix. What version of systemd is running? Don't care. How close is the clock to Coordinated Universal Time? Don't care. It's an appliance and the time on the front is blinking :P (I spent most of my free time this week unbreaking my Beaglebone that I ostensibly don't treat that way -- I log in and fuck with shit. Though when debugging failed I just blew everything away and copied over what I saved in the project's Git repo. It was enough to be back up and running with no loss of functionality. I guess the key is: don't let it run away from you -- it can be an endless time and energy sink.)
5h 5y ago
What air quality sensor are you using?
5e92cb50239222b 5y ago
You seem to have relatively clean air already. I probably wouldn't even bother with air purifiers in such a situation. Where did you buy air filters? I live in a third-world country and couldn't find them anywhere, so I had to buy a factory-built purifier. It really struggles to keep up when it's 1000+ µg/m³ outside. I'd like to add a second one (preferably DIY).
- DeRock 5y ago
  Sure, air quality is relative, but 100 AQI is the point where I start getting headaches. Obviously it can get much worse. I got the air filters on Amazon, which can be US centric, but usually you would get them at a home/hardware store. They are made for slotting into a furnace/HVAC set up. For places where that is less common, they may be harder to find.
- dynm 5y ago
  > You seem to have relatively clean air already. I probably wouldn't even bother with air purifiers in such a situation. By my estimates, a lifelong exposure to 33 µg/m³ rather than 0 µg/m³ would on average result in a loss of around 1 disability adjusted life year. https://dynomight.net/air/#a-heuristic-to-quantify-harms https://dynomight.net/air/#a-heuristic-to-quantify-harms Obviously this is very hard to estimate and you shouldn't trust this as anything more than at most a rough order of magnitude estimate. But it does suggest that the ambient levels they are experiencing are worth reducing if you can do it easily.
  - fighterpilot 5y ago
    Might those numbers might be exaggerated a bit due to confounders? Specifically, the high density and traffic causing stress.
    - dynm 5y ago
      It's entirely possible! But my perspective is that there's a very one-sided risk. It's extremely unlikely that particles are beneficial. Thus, given the uncertainty I think it's good decision theory to run a purifier, especially given how easy it is relative to other lifestyle changes that could plausibly have a benefit of the same magnitude.
sosuke 5y ago
I've been doing this wrong all along then? I've got my filter on the outtake side. What is the difference I wonder.
- SamBam 5y ago
  From my understanding the biggest difference is the blades not getting covered in grime, because you're pre-filtering the air. I've also heard airflow dynamics arguments, but I feel like I've heard them argued in both directions.
  - ncmncm 5y ago
    You can use two fans, one on intake, one on exhaust. Or three, if you have a particularly fine filter. But building another whole unit to run in another room might be better. With a #9, one-inch filter, a single fan does fine.
- tejtm 5y ago
  The difference is your "fan/blower" will not function as well as a "compressor". You want to vent towards the largest, least constrained volume available, from higher constraints towards lower constraints.
- MrStonedOne 5y ago
  Outtake muffles agitation from the airflow. Intake still allows the air coming out to be more turbulent, mixing with the existing air better and giving it more "throw" in larger spaces.
- sreedhark 5y ago
  You should be fine, here is the comparison https://www.youtube.com/watch?v=zE4qmN_EOXw https://www.youtube.com/watch?v=zE4qmN_EOXw edit1: exact time of the result https://youtu.be/zE4qmN_EOXw?t=250 https://youtu.be/zE4qmN_EOXw?t=250
sokoloff 5y ago
> Both filters are on the intake side of the box fan. This means you don't need a bungee cord because the intake has negative pressure, the filters just "stick" I agree with putting them on the intake side, but I still want them to stay put when the fan is turned off (with the switch or to move it to another outlet or in a power outage).
- matmann2001 5y ago
  There are large rubber bands you can buy specifically to hold the filter in place on the box fan. I've seen them on Amazon.
sdze 5y ago
Is such device useful to minimise dusting of objects in the room? Like plants, cupboards etc. ? Do you still have to clean dust in the room?
- 5e92cb50239222b 5y ago
  After using a purifier for two years pretty much non-stop (close to 24/7) I am pretty certain they don't help with dust at all. That's not why we install them, though.
  - jaytaylor 5y ago
    Re: home dust filtration How can you even search for this? Google results are not relevant to dust at all: https://www.google.com/search?q=diy+air+dust+filter https://www.google.com/search?q=diy+air+dust+filter This is a really strong example of how bad goog sucks for long-tail queries. SEO spammed: https://www.google.com/search?q=home+dust+filtration+old+house https://www.google.com/search?q=home+dust+filtration+old+hou...
    - hawtkey 5y ago
      I've found that tacking 'pdf' onto search queries gets through some of the SEO garbage. For instance I did 'home dust filtration pdf' and found this pdf: https://www.epa.gov/sites/default/files/2018-07/documents/residential_air_cleaners_-_a_technical_summary_3rd_edition.pdf https://www.epa.gov/sites/default/files/2018-07/documents/re... which cites this paper about deposition rates of different particle sizes: https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=860943 https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=86094...
    - IncRnd 5y ago
      > How can you even search for this? Google results are not relevant to dust at all: Try this: https://www.google.com/search?q=diy+air+%22dust+filter%22 https://www.google.com/search?q=diy+air+%22dust+filter%22
- malfist 5y ago
fighterpilot 5y ago
How strong is the air flow with the filter attached? Is it a slow trickle or can you really feel a decent amount coming out? Also, 4 inches is quite a lot of depth for a MERV filter, could you elaborate on this point?
- amluto 5y ago
  4 inches is deep for a standard dimensioned MERV-rated filter. It’s normal for a high quality but sadly usually proprietary fancy HVAC filter (Aprilaire, Lennox, etc).
  - fighterpilot 5y ago
    That's true, but I want to know what they meant when they said the 4-inch pleating is designed to reduce air resistance. Since it's an unusually large amount of depth for a MERV filter, I would expect the opposite to happen?
    - rootusrootus 5y ago
      Air resistance goes down with thicker filters because filter area goes up.
      - fighterpilot 5y ago
        Ok, yes. Do we know how the air resistance/air flow varies as a function of surface area? Is it almost linear? I'm wondering how important it is.
        ncmncm 5y ago
        Feel the air coming out, vs without a filter. The slower the air is, the fewer opportunities you get to trap each dust grain. Overall miss rate improves exponentially with airflow speed.
        5y ago
agumonkey 5y ago
thanks, do you have a website to put updates ? I'd love to know how it goes long term wise (filter changes, average air quality, your health)
justinzollars 5y ago
How do you measure your air quality? What sensor do you use? I have a similar setup and I'd like to measure the results. I know its working because I don't smell smoke, but I'm curious to see a measurement
j0e1 5y ago
Nice setup! Could you also share the names (brands/model, e.g. 3M Filtrete 20x20x4) of the three components? I see a few options out there but rather go with something that is vouched for here.
bitcoinmoney 5y ago
What sensor do you use?
FullKirby 5y ago
Thank you for sharing !

by DeRock 5y ago

chana_masala 5y ago

Thanks for sharing, that's neat how simple it is. What air quality sensor setup do you have?

DeRock 5y ago
HM3301: https://wiki.seeedstudio.com/Grove-Laser_PM2.5_Sensor-HM3301/ https://wiki.seeedstudio.com/Grove-Laser_PM2.5_Sensor-HM3301... Attached over I2C to an ESP32 running ESPHome: https://esphome.io/#air-quality https://esphome.io/#air-quality Which in turn reports to a raspberry pi running Home Assistant: https://www.home-assistant.io/installation/ https://www.home-assistant.io/installation/ Took about 20 mins to set everything up.
- jve 5y ago
  > Took about 20 mins to set everything up. Given you have Home Assistant installed and have previously used ESPHome. And attached wires. Otherwise, you may be up to a journey that takes many hours/days. That's the difference experience makes :)
  - DeRock 5y ago
    The only thing set up was the raspberry pi having an OS installed. Had never used HA or ESPHome before. I was shocked how easy it was if you're comfortable with a terminal. I'd never even used docker before. My steps were: 1. Install docker 2. Install/run HA through docker 3. Install/run ESPHome through docker (there's a config wizard) 4. Edit the ESPHome .yaml from (3) to my preferences 5. Connect 4 wires from the ESP32 to the air quality sensor 6. Plug ESP32 USB to RPi 7. Run docker esphome on the above yaml. This compiles, flashes, and boots your ESP32, auto-connecting to your network 8. Add the ESP air quality sensor to HA through the web GUI
    - jve 5y ago
      That's (almost) exactly what I did and without prior docker experience. I must admin it was less hassle with docker, but still docs for particular containers had to be read to understand configuration options. + setting up for external access, letsencrypt and tying that everything within docker-compose. I didn't manage to do it in 20minutes, but more like full working day maybe? Anyway, HA is recommended. Haven't tried ESPHome, but Tasmota is an alternative that also does the job, if you someone ever wants to research the options.
  - jrockway 5y ago
    Turnkey microcontroller projects can be really quick. Adafruit and Sparkfun sell many of their breakout boards with special cables for I2C now, so you might not even have to solder anything. From there, you can drag a Python script to the microcontroller (which appears on your PC as a flash drive). Building enclosures for these projects used to be an annoyance, but everyone provides CAD models of their stuff now, so you just kind of lay it out in your CAD program, extrude a box around it, and print it out. Never been a better time than now to be building sensors and that sort of thing. (Even with the STM32 shortage!) As for the Raspberry Pi -- my rule is to treat embedded systems like hardware. Download a Linux image with the software you want on it, copy it to an SD card, plug that in, and go. I use this model for Octopi and while I might have changed the password and uploaded a profile for my printer file, that's it. If the RPI blows itself up, $35 and 5 minute fix. What version of systemd is running? Don't care. How close is the clock to Coordinated Universal Time? Don't care. It's an appliance and the time on the front is blinking :P (I spent most of my free time this week unbreaking my Beaglebone that I ostensibly don't treat that way -- I log in and fuck with shit. Though when debugging failed I just blew everything away and copied over what I saved in the project's Git repo. It was enough to be back up and running with no loss of functionality. I guess the key is: don't let it run away from you -- it can be an endless time and energy sink.)

5h 5y ago

What air quality sensor are you using?

5e92cb50239222b 5y ago

You seem to have relatively clean air already. I probably wouldn't even bother with air purifiers in such a situation. Where did you buy air filters? I live in a third-world country and couldn't find them anywhere, so I had to buy a factory-built purifier. It really struggles to keep up when it's 1000+ µg/m³ outside. I'd like to add a second one (preferably DIY).

DeRock 5y ago
Sure, air quality is relative, but 100 AQI is the point where I start getting headaches. Obviously it can get much worse. I got the air filters on Amazon, which can be US centric, but usually you would get them at a home/hardware store. They are made for slotting into a furnace/HVAC set up. For places where that is less common, they may be harder to find.
dynm 5y ago
> You seem to have relatively clean air already. I probably wouldn't even bother with air purifiers in such a situation. By my estimates, a lifelong exposure to 33 µg/m³ rather than 0 µg/m³ would on average result in a loss of around 1 disability adjusted life year. https://dynomight.net/air/#a-heuristic-to-quantify-harms https://dynomight.net/air/#a-heuristic-to-quantify-harms Obviously this is very hard to estimate and you shouldn't trust this as anything more than at most a rough order of magnitude estimate. But it does suggest that the ambient levels they are experiencing are worth reducing if you can do it easily.
- fighterpilot 5y ago
  Might those numbers might be exaggerated a bit due to confounders? Specifically, the high density and traffic causing stress.
  - dynm 5y ago
    It's entirely possible! But my perspective is that there's a very one-sided risk. It's extremely unlikely that particles are beneficial. Thus, given the uncertainty I think it's good decision theory to run a purifier, especially given how easy it is relative to other lifestyle changes that could plausibly have a benefit of the same magnitude.

sosuke 5y ago

I've been doing this wrong all along then? I've got my filter on the outtake side. What is the difference I wonder.

SamBam 5y ago
From my understanding the biggest difference is the blades not getting covered in grime, because you're pre-filtering the air. I've also heard airflow dynamics arguments, but I feel like I've heard them argued in both directions.
- ncmncm 5y ago
  You can use two fans, one on intake, one on exhaust. Or three, if you have a particularly fine filter. But building another whole unit to run in another room might be better. With a #9, one-inch filter, a single fan does fine.
tejtm 5y ago
The difference is your "fan/blower" will not function as well as a "compressor". You want to vent towards the largest, least constrained volume available, from higher constraints towards lower constraints.
MrStonedOne 5y ago
Outtake muffles agitation from the airflow. Intake still allows the air coming out to be more turbulent, mixing with the existing air better and giving it more "throw" in larger spaces.
sreedhark 5y ago
You should be fine, here is the comparison https://www.youtube.com/watch?v=zE4qmN_EOXw https://www.youtube.com/watch?v=zE4qmN_EOXw edit1: exact time of the result https://youtu.be/zE4qmN_EOXw?t=250 https://youtu.be/zE4qmN_EOXw?t=250

sokoloff 5y ago

> Both filters are on the intake side of the box fan. This means you don't need a bungee cord because the intake has negative pressure, the filters just "stick" I agree with putting them on the intake side, but I still want them to stay put when the fan is turned off (with the switch or to move it to another outlet or in a power outage).

matmann2001 5y ago
There are large rubber bands you can buy specifically to hold the filter in place on the box fan. I've seen them on Amazon.

sdze 5y ago

Is such device useful to minimise dusting of objects in the room? Like plants, cupboards etc. ? Do you still have to clean dust in the room?

5e92cb50239222b 5y ago
After using a purifier for two years pretty much non-stop (close to 24/7) I am pretty certain they don't help with dust at all. That's not why we install them, though.
- jaytaylor 5y ago
  Re: home dust filtration How can you even search for this? Google results are not relevant to dust at all: https://www.google.com/search?q=diy+air+dust+filter https://www.google.com/search?q=diy+air+dust+filter This is a really strong example of how bad goog sucks for long-tail queries. SEO spammed: https://www.google.com/search?q=home+dust+filtration+old+house https://www.google.com/search?q=home+dust+filtration+old+hou...
  - hawtkey 5y ago
    I've found that tacking 'pdf' onto search queries gets through some of the SEO garbage. For instance I did 'home dust filtration pdf' and found this pdf: https://www.epa.gov/sites/default/files/2018-07/documents/residential_air_cleaners_-_a_technical_summary_3rd_edition.pdf https://www.epa.gov/sites/default/files/2018-07/documents/re... which cites this paper about deposition rates of different particle sizes: https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=860943 https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=86094...
  - IncRnd 5y ago
    > How can you even search for this? Google results are not relevant to dust at all: Try this: https://www.google.com/search?q=diy+air+%22dust+filter%22 https://www.google.com/search?q=diy+air+%22dust+filter%22
malfist 5y ago

fighterpilot 5y ago

How strong is the air flow with the filter attached? Is it a slow trickle or can you really feel a decent amount coming out? Also, 4 inches is quite a lot of depth for a MERV filter, could you elaborate on this point?

amluto 5y ago
4 inches is deep for a standard dimensioned MERV-rated filter. It’s normal for a high quality but sadly usually proprietary fancy HVAC filter (Aprilaire, Lennox, etc).
- fighterpilot 5y ago
  That's true, but I want to know what they meant when they said the 4-inch pleating is designed to reduce air resistance. Since it's an unusually large amount of depth for a MERV filter, I would expect the opposite to happen?
  - rootusrootus 5y ago
    Air resistance goes down with thicker filters because filter area goes up.
    - fighterpilot 5y ago
      Ok, yes. Do we know how the air resistance/air flow varies as a function of surface area? Is it almost linear? I'm wondering how important it is.
      - ncmncm 5y ago
        Feel the air coming out, vs without a filter. The slower the air is, the fewer opportunities you get to trap each dust grain. Overall miss rate improves exponentially with airflow speed.
        5y ago

agumonkey 5y ago

thanks, do you have a website to put updates ? I'd love to know how it goes long term wise (filter changes, average air quality, your health)

justinzollars 5y ago

How do you measure your air quality? What sensor do you use? I have a similar setup and I'd like to measure the results. I know its working because I don't smell smoke, but I'm curious to see a measurement

j0e1 5y ago

Nice setup! Could you also share the names (brands/model, e.g. 3M Filtrete 20x20x4) of the three components? I see a few options out there but rather go with something that is vouched for here.

bitcoinmoney 5y ago

What sensor do you use?

FullKirby 5y ago

Thank you for sharing !