Build a do-it-yourself home air purifier for about $25(uofmhealth.org)
uofmhealth.org
Build a do-it-yourself home air purifier for about $25
https://www.uofmhealth.org/news/sinus-hepa-0630
342 comments
I built my own air purifier in 2016, living in London, I was living in a basement and was having breathing problems due to mould. My landlady was gaslighting me at the time, so I built the air purifier. It worked for a while but mould spores cling to the paper filter and eventually grow into the filter material. I think Dyson uses glass fiber filter to stop this problem. My filter helped a lot, but eventually I had sclerosis infection on my brain and ended up in hospital with lung infection and brain lesion, still recovering after two years, and I will never be my old self again. I was subletting so had no grounds for complaint, I had to choose between homelessness or phoning a distant relative I hadn't spoken to for 24years, I chose the latter and I think it's the reason I'm still here.
Important tip: if you set up an air purifier in your home, make sure to plug all drafts around your house: windows, doors, etc. Even a DIY purifier with small airflow can make your indoor air excellent if given enough time to do so and no leaks to fight against.
If you want to get some fresh air in your home, do not leave a window half-open all day long—instead, open all your windows at once to cycle the air as fast as possible, then close them again and let the purifier do its job. If you do that in the morning (ideally just before leaving, if you aren't staying home), you'll have great air quality through the entire evening and night.
Since we're on HN, I'll also mention a toy project I built a while back [0]. It uses a Raspberry Pi to read particulate matter sensor mesurements over serial link from a Dylos 1100 Pro, then pipes it into Redis and InfluxDB and ultimately Grafana for presentation. I've used it to track the air quality in my home in for the past year or so and it's pretty fun. In my case, cooking is usually the biggest contributor to poor indoor air quality!
[0] https://github.com/peferron/air-quality
If you want to get some fresh air in your home, do not leave a window half-open all day long—instead, open all your windows at once to cycle the air as fast as possible, then close them again and let the purifier do its job. If you do that in the morning (ideally just before leaving, if you aren't staying home), you'll have great air quality through the entire evening and night.
Since we're on HN, I'll also mention a toy project I built a while back [0]. It uses a Raspberry Pi to read particulate matter sensor mesurements over serial link from a Dylos 1100 Pro, then pipes it into Redis and InfluxDB and ultimately Grafana for presentation. I've used it to track the air quality in my home in for the past year or so and it's pretty fun. In my case, cooking is usually the biggest contributor to poor indoor air quality!
[0] https://github.com/peferron/air-quality
Generally there are two classes of objects that you want to filter for.
Particulates and VOC (Volatile Organic Compounds). Think of particulates as specs of dust with varying size and VOC's as random chemical compounds such as spray paint, smoke, oders.
The general go-to clean room/industrial filter stack is Prefilter(F5 Bag)->HEPA->Activated Carbon. The pre-filter catches all the big particulates to prevents clogging the HEPA filter. The HEPA filter catches all of the really small particulates. The activated carbon captures most of the VOC's/oder/smoke.
The official way to monitor when a particulate filter is bad, is to measure the pressure drop across the filter, and compare to manufacture specs. For the carbon filters, you would install a gas sensor measuring whatever chemical your trying to scrub. When there is a spike in that particular gas compound from your sensor. You know the carbon filter is saturated, and should be changed.
It looks like the the filter mentioned in the article video,combines all the filter products into a single product. Nice! If your air handler can manage the increased pressure drops, please buy the most legit filters you can buy. It's literally the cheapest insurance you can buy.
Particulates and VOC (Volatile Organic Compounds). Think of particulates as specs of dust with varying size and VOC's as random chemical compounds such as spray paint, smoke, oders.
The general go-to clean room/industrial filter stack is Prefilter(F5 Bag)->HEPA->Activated Carbon. The pre-filter catches all the big particulates to prevents clogging the HEPA filter. The HEPA filter catches all of the really small particulates. The activated carbon captures most of the VOC's/oder/smoke.
The official way to monitor when a particulate filter is bad, is to measure the pressure drop across the filter, and compare to manufacture specs. For the carbon filters, you would install a gas sensor measuring whatever chemical your trying to scrub. When there is a spike in that particular gas compound from your sensor. You know the carbon filter is saturated, and should be changed.
It looks like the the filter mentioned in the article video,combines all the filter products into a single product. Nice! If your air handler can manage the increased pressure drops, please buy the most legit filters you can buy. It's literally the cheapest insurance you can buy.
Huh! I independently "invented" this myself a couple of days ago when the Camp Fire blanketed the bay area in smoke. I got a 20x20 filter and some duct tape from Home Depot and a box fan from Target. (After discovering that Home Depot only sells fans in the summer.)
I don't think I was the only one, though. HD was doing a brisk trade in 20x20 filters, and I think I bought the last box fan at any Target in the entire bay area.
My "creation": https://i.imgur.com/jeJfqeW.jpg
I don't think I was the only one, though. HD was doing a brisk trade in 20x20 filters, and I think I bought the last box fan at any Target in the entire bay area.
My "creation": https://i.imgur.com/jeJfqeW.jpg
Can we talk about Molekule? Their team and some SF tech community folks have been plugging it all over Twitter during this tragic wildfire crisis. But it seems like snake oil to me. It’s $800. Certainly for smoke particles it can’t possibly offer any more protection than a standard HEPA filter. But even for its claimed ability to nuke VOCs, the claim seems ridiculous. While particles can deterioriate under prolonged exposure, the airflow must be too high and the exposure too short to make much of a difference.
What gets me is how these guys misuse “science marketing” to play on people’s fears about germs. Add the shameless exploitation of a real tragedy here.
What gets me is how these guys misuse “science marketing” to play on people’s fears about germs. Add the shameless exploitation of a real tragedy here.
Note that restricting airflow on a radial fan can cause the motor to heat up. Make sure you get a 20-inch fan with a fuse. To reduce heat, increase air flow by making a box with three filters and by using 2 inch deep filters. Also, when I built my three filter "box" last fall, I was able to order a set of three MERV-13 20x20x2 filters directly from Nordic Pure for less than what they cost on Amazon. Finally, to make a cube, cut the remaining sides from the filter box. Then roughly tape it together with small pieces of duct tape. When the filters and panels are in the right spots, seal it completely with duct tape. Remember to put the box of filters on the "pull" side of the fan with right sides of the filters facing outwards.
I spent the weekend researching, implementing, etc. air filtration as one of those affected by the CA fires. It was worth it!
The first step for me was getting a device to measure particles in the air. The air quality index (AQI) is an aggregate score that is made up of contributions from several harmful components. Of these, the quantity (weight/volume) of small particles (<2.5um) is often the large contributor. This is called the PM2.5.
Directly measuring PM2.5 is very hard, requiring a device that eliminates the larger particles from the air (typically a cyclonic separator it seems) combined with some way of capturing and weighing of the very small quantity of remaining particles (we're talking ug/m^3).
Many home air quality sensors instead measure the count/volume of particles larger than 2.5 um and call that the "2.5um measurement". You can see the problem. I bought a laser particle counted called Dylos DC1100 Pro. The Dylos measures particles counts larger than 2.5um as is common, but also counts particles larger than 0.5um. Of these two numbers, the 2.5 count is only vaguely correlated with the actual PM2.5 measure, but the 0.5um count is highly correlated.
A bit of internet research (it seems many people have used the Dylos meter in various projects) and I was able to construct a scale to correlate 0.5um+ counts to PM2.5, and therefore AQI. (0.005*count~=ug/m^3)
OK, all that done, to the filtration. First, I installed 3M 1550 MPR furnace filters (~MERV11). The "1550" is a measure invented by 3M 'MicroParticleRating' (or something) and is supposed to speak to how well the filters remove small particles. However these furnace filters don't really knock down very small particle counts in once pass. Sure enough, putting the particle meter at an air duct, the large (2.5+) particle count was way down, but the small particle count was only down a little bit (15-25%?) from the ambient air. Net effect is that after running for several days my house numbers are about 1/3 of the outside air counts.
I also bought a BlueAir HEPA filter for my bedrooms. HEPA is supposed to be 99+% effective for particles 0.3um and up. This filter is in a whole different league. The particle counter placed on top of the filter returns near-zero small particle counts and does a much better job eliminating smells. The room they were in got down to 1/10 of outside levels.
Overall I'm glad I got both types of filters, we are sleeping better, and the meter was very helpful to understand what was going on.
The first step for me was getting a device to measure particles in the air. The air quality index (AQI) is an aggregate score that is made up of contributions from several harmful components. Of these, the quantity (weight/volume) of small particles (<2.5um) is often the large contributor. This is called the PM2.5.
Directly measuring PM2.5 is very hard, requiring a device that eliminates the larger particles from the air (typically a cyclonic separator it seems) combined with some way of capturing and weighing of the very small quantity of remaining particles (we're talking ug/m^3).
Many home air quality sensors instead measure the count/volume of particles larger than 2.5 um and call that the "2.5um measurement". You can see the problem. I bought a laser particle counted called Dylos DC1100 Pro. The Dylos measures particles counts larger than 2.5um as is common, but also counts particles larger than 0.5um. Of these two numbers, the 2.5 count is only vaguely correlated with the actual PM2.5 measure, but the 0.5um count is highly correlated.
A bit of internet research (it seems many people have used the Dylos meter in various projects) and I was able to construct a scale to correlate 0.5um+ counts to PM2.5, and therefore AQI. (0.005*count~=ug/m^3)
OK, all that done, to the filtration. First, I installed 3M 1550 MPR furnace filters (~MERV11). The "1550" is a measure invented by 3M 'MicroParticleRating' (or something) and is supposed to speak to how well the filters remove small particles. However these furnace filters don't really knock down very small particle counts in once pass. Sure enough, putting the particle meter at an air duct, the large (2.5+) particle count was way down, but the small particle count was only down a little bit (15-25%?) from the ambient air. Net effect is that after running for several days my house numbers are about 1/3 of the outside air counts.
I also bought a BlueAir HEPA filter for my bedrooms. HEPA is supposed to be 99+% effective for particles 0.3um and up. This filter is in a whole different league. The particle counter placed on top of the filter returns near-zero small particle counts and does a much better job eliminating smells. The room they were in got down to 1/10 of outside levels.
Overall I'm glad I got both types of filters, we are sleeping better, and the meter was very helpful to understand what was going on.
Nifty idea, but I'm not sure I agree with the technique used to prove effectiveness:
https://www.youtube.com/watch?v=kH5APw_SLUU
The narrator puts a particle counter in front of the fan and notes the 90% reduction. So far so good.
The problem is extrapolating this result to the entire room. Yes, maybe you'd get close to 90% if the device were allowed to run a few days.
On the other hand, it could leave the situation worse (by blowing existing particulates around) or unimproved (by failing to filter room air efficiently enough.
Either way, I'd like to see see a controlled study. Two identical rooms with identical usage. One gets a homemade filter. The other gets just a fan of the same make and model, maybe with a dummy filter to baffle airflow.
What's the average particle count in both rooms after, say one week?
https://www.youtube.com/watch?v=kH5APw_SLUU
The narrator puts a particle counter in front of the fan and notes the 90% reduction. So far so good.
The problem is extrapolating this result to the entire room. Yes, maybe you'd get close to 90% if the device were allowed to run a few days.
On the other hand, it could leave the situation worse (by blowing existing particulates around) or unimproved (by failing to filter room air efficiently enough.
Either way, I'd like to see see a controlled study. Two identical rooms with identical usage. One gets a homemade filter. The other gets just a fan of the same make and model, maybe with a dummy filter to baffle airflow.
What's the average particle count in both rooms after, say one week?
I do this and it works wonders if you have pets.
Tips:
- run this homemade air purifier when you are vacuuming, as that tends to agitate particulates a lot
- get 2 filters, a cheap low grade and a premium, high-HEPA-rated filter. Stack them together and you can replace the cheap one frequently and the expensive one less frequently.
I wonder if you'd put cotton wool, how effective it would be. Here is my set up:
- I bought XIAOMI Mi Air Purifier 2 straight from China for $137.00 and spent 1 euro on a EU plug. It's so quiet that I can sleep next to it, looks nice and it's quite compact, so doesn't take up much space. It has a particle detector to adjust the fan speed. The app is useless, so a cheaper version without WiFi and bluetooth would be great.
- Buy some HEPA filters to put into window ventilation. You may want to remove some plastic inside to increase the flow http://img.archiexpo.com/images_ae/photo-g/69621-5895915.jpg
- Buy roomba like vacuum cleaner https://www.goodcheapandfast.com/articles/best-robot-vacuums
It will cost you less than 500$ to buy these and about 55$/year for new filters. It is worth the money. The air quality is much better (I'm allergic and I haven't had any problem with my sinus since).
What is more, is it worth it. It will save you time cleaning your place (about 10h/year)
Anyone has tried robot vacuums with mop or automatic dirt disposal function?
- I bought XIAOMI Mi Air Purifier 2 straight from China for $137.00 and spent 1 euro on a EU plug. It's so quiet that I can sleep next to it, looks nice and it's quite compact, so doesn't take up much space. It has a particle detector to adjust the fan speed. The app is useless, so a cheaper version without WiFi and bluetooth would be great.
- Buy some HEPA filters to put into window ventilation. You may want to remove some plastic inside to increase the flow http://img.archiexpo.com/images_ae/photo-g/69621-5895915.jpg
- Buy roomba like vacuum cleaner https://www.goodcheapandfast.com/articles/best-robot-vacuums
It will cost you less than 500$ to buy these and about 55$/year for new filters. It is worth the money. The air quality is much better (I'm allergic and I haven't had any problem with my sinus since).
What is more, is it worth it. It will save you time cleaning your place (about 10h/year)
Anyone has tried robot vacuums with mop or automatic dirt disposal function?
I made a custom wooden computer case with 8 120mm fans and a furnace filter over the intake. The computer side is positive pressure and is as clean as the day I built it 4 years ago.
I buy filters in bulk from McMaster Carr for $5 apiece.
I buy filters in bulk from McMaster Carr for $5 apiece.
Check out the blog
http://particlecounting.tumblr.com/
The writer has tested a lot of combinations of fans and filters (Simple, HEPA, Activated Charcoal). It's astonishingly easy to build a combination that costs way less than a "professional" Air filter.
The writer has put his findings into a "social startup" that builts these simple, but very effective airfilters in some developing countries:
https://smartairfilters.com/cn/en/product-category/diy-air-p...
http://particlecounting.tumblr.com/
The writer has tested a lot of combinations of fans and filters (Simple, HEPA, Activated Charcoal). It's astonishingly easy to build a combination that costs way less than a "professional" Air filter.
The writer has put his findings into a "social startup" that builts these simple, but very effective airfilters in some developing countries:
https://smartairfilters.com/cn/en/product-category/diy-air-p...
If anyone is looking for general air purifier recommendations. I'm a huge fan of Coway systems.
I have pretty bad allergies purchased a Coway Airmega 300 for my 850sq ft studio. I've had it for about 6 months and been incredibly happy with it. I wrote some initial thoughts about it here.
https://productdork.com/t/coway-airmega-300-vs-400/56
It has to be the best looking air filter on the market—I wanted something that would look good in my place when I have people over. Beyond that it is extremely well designed and the pre-filters are super easy to clean. I got mine on sale for about $400.
For smaller rooms the Coway mighty is a better and more affordable pick. It doesn't look as nice, but it is currently at the top of The Wirecutter's air purifier recommendations. You can find it on sale for around $180.
https://thewirecutter.com/reviews/best-air-purifier/
I have pretty bad allergies purchased a Coway Airmega 300 for my 850sq ft studio. I've had it for about 6 months and been incredibly happy with it. I wrote some initial thoughts about it here.
https://productdork.com/t/coway-airmega-300-vs-400/56
It has to be the best looking air filter on the market—I wanted something that would look good in my place when I have people over. Beyond that it is extremely well designed and the pre-filters are super easy to clean. I got mine on sale for about $400.
For smaller rooms the Coway mighty is a better and more affordable pick. It doesn't look as nice, but it is currently at the top of The Wirecutter's air purifier recommendations. You can find it on sale for around $180.
https://thewirecutter.com/reviews/best-air-purifier/
I wonder: if one is generally healthy and the air quality is unproblematic, should one get an air filter? Does air filtration potentially lower long term immunity and make us less tolerant to particulates?
I worry about the long term effects of being “too clean”, that is, I think there’s something to hygiene theory of disease. The body needs small stressors and perturbations in order to thrive.
I worry about the long term effects of being “too clean”, that is, I think there’s something to hygiene theory of disease. The body needs small stressors and perturbations in order to thrive.
I built a similar model over the weekend: https://twitter.com/valarauca1/status/1061362369702445056
Used an existing box fan. I had to buy duct tape ($3) and the filter I used one rated for 0.1micron pollen and viruses cost me $17 (rounding up after tax). I cut up a plastic safeway bag to make the seal around it. Seeing as most smoke particles is around 2.5-.5 micron I figured it'd be okay.
I threw this together at about 7am on Saturday after I woke up coughing my lungs out at 6am (I live in the bay area). Just a quick trip down the the Homeless Despot to get the parts and throw it together.
All things consider it works great. The air in my apartment is easy to breath, but if I leave without a respirator (even today) I cough uncontrollably.
---
As of Tuesday evening it has been running for 4 days straight (no overheating). And has started to become noticeably brown. Needless to say I'm thankful for it.
Used an existing box fan. I had to buy duct tape ($3) and the filter I used one rated for 0.1micron pollen and viruses cost me $17 (rounding up after tax). I cut up a plastic safeway bag to make the seal around it. Seeing as most smoke particles is around 2.5-.5 micron I figured it'd be okay.
I threw this together at about 7am on Saturday after I woke up coughing my lungs out at 6am (I live in the bay area). Just a quick trip down the the Homeless Despot to get the parts and throw it together.
All things consider it works great. The air in my apartment is easy to breath, but if I leave without a respirator (even today) I cough uncontrollably.
---
As of Tuesday evening it has been running for 4 days straight (no overheating). And has started to become noticeably brown. Needless to say I'm thankful for it.
Where do you get these parts in the UK?
The MERV 13 20" filter is 140GBP on amazon.co.uk and 20" box fans are 40-50GBP.
The MERV 13 20" filter is 140GBP on amazon.co.uk and 20" box fans are 40-50GBP.
Is there an advantage to attaching the filter to the front of the fan so air is blown through it (as shown in the video) versus taping it to the back of the fan so air is sucked through it? Just curious if that would make any difference. It might be easier to get the filter to stay if it's getting sucked to the fan.
I used a very thick (4") filter rated for smoke particles when the wildfires this year blew their smoke down to Seattle. The filter went from white to a very interesting shade of grey in 3 days. Wife was able to sleep again though, so it does work very well in my experience. (20x20 fan, filter on intake side)
I been pondering about this solution for months since my air purifier died back early summer. I also have an additional idea to make it more automatic by using a raspberry pi, hooking it up to a powerswitch tail (essentially cutting power to a fan) and have it automatically turn on and off depending on time of day, etc.
Repurpose this device as a jerky dehydrator too:
https://altonbrown.com/beef-jerky-recipe/jerky-blowhard-3000...
They used to sell these--box fans with connections for furnace filters. I found it strange that they never caught on, and now you can't find them anywhere.
I was looking up air quality monitors but can't seem to find any on amazon with a calibration certificate that will accurately measure 0.3 micro particles. Am I the only one who thinks this is a great opportunity for a smart product with an app that has the features of a professional air quality monitor and simple UI / UX? If such product exists, does anyone know where I can find it?
I've been running a 3M Filtrete MPR 2800 in my furnace filter. https://www.purpleair.com/ confirms it works. There house averages maybe 60 PM 2.5 vs 200 outside.
Don't know how good it is for furnace, but it hardly runs otherwise in Northern CA.
Edit: plants do nothing to particle matter in air they can soak up co2, benzene, formaldehyde etc but do ample resesrch before placing plants in your bedroom. Typically snake plants are fine in bedroom as they don't give out CO2 at night.
There is no need for an air purifier if you have ample light in your room. Just plant a few indoor plants
Peace lily
Rubber plant
Snake plant
Spider plant
Aloe vera
Money plant
Orchid
NASA has done a study in the 80s and these plants have purified a lot of harmful gases including Benzene, formaldehyde, CO etc
Please use more plants!! And on top of that few plants like Snake, Aloe give oxygen during day and night so they are refreshing (as in they don't just clean air they give oxygen as well) and plants are cheaper and require just water and fertilizer every once in a while.
I own 40+ plants in my balcony garden itself. I've experienced these effects first hand!
There is no need for an air purifier if you have ample light in your room. Just plant a few indoor plants
Peace lily
Rubber plant
Snake plant
Spider plant
Aloe vera
Money plant
Orchid
NASA has done a study in the 80s and these plants have purified a lot of harmful gases including Benzene, formaldehyde, CO etc
Please use more plants!! And on top of that few plants like Snake, Aloe give oxygen during day and night so they are refreshing (as in they don't just clean air they give oxygen as well) and plants are cheaper and require just water and fertilizer every once in a while.
I own 40+ plants in my balcony garden itself. I've experienced these effects first hand!
So I did this with a cheap $15 box fan and a MERV 13 filter. It performs very poorly, the filter impedes the airflow too much and the fan actually will intake most of the airflow from the front corners of the output side because it's less resistance. Axial flow fans only operate efficiently at low static pressures. This is why your home forced air system uses a centrifugal blower, which is more efficient at high static pressures.
tl;dr I'd use a MERV 11 or less on a cheap box fan. You aren't going to make a Class 100 clean room out of your house with this kind of setup.
tl;dr I'd use a MERV 11 or less on a cheap box fan. You aren't going to make a Class 100 clean room out of your house with this kind of setup.
Similar items are commercially available:
"The Fan Buddy is an electrostatic washable fan filter that attracts and captures airborne dust, pollen, dust-mite debris, lint, mold spores and pet dander. It will also help reduce smoke and smog. This Fan Buddy fits on most 20 in. box fans... "
https://www.homedepot.com/p/Fan-Buddy-20-in-x-20-in-x-1-in-W...
"The Fan Buddy is an electrostatic washable fan filter that attracts and captures airborne dust, pollen, dust-mite debris, lint, mold spores and pet dander. It will also help reduce smoke and smog. This Fan Buddy fits on most 20 in. box fans... "
https://www.homedepot.com/p/Fan-Buddy-20-in-x-20-in-x-1-in-W...
Might be a stupid question but does this work for external air pollution? I live at the 20th floor in a city with terrible air quality and we open the windows once or twice a day.
I've been using a setup like this for the past year.
I use a 4" think filter to reduce strain on the motor though (it's pleated, so a lot more surface area to pull air through than the thinner ones), the idea being reduced strain on the motor.
I also stick a carbon pre-filter in front of it.
I get smoke wafting in from outside via window air conditioner - and I think my neighbor occasionally smokes in his room.
I'm planning to setup another to better cover my open floorplan.
I get smoke wafting in from outside via window air conditioner - and I think my neighbor occasionally smokes in his room.
I'm planning to setup another to better cover my open floorplan.
In case you're curious how this does with wildfire smoke -- Oakland 1 bedroom, put a 14"x20" MERV 13 (filtrete blue) filter on a box fan (covering the extra 6" with paper). Had a PMS5003 from adafruit monitoring before and after. In the span of 3 hours indoor PM2.5 dropped from 25 to 5 ug/m3 and has stayed low since.
https://imgur.com/IxdxhV2
https://imgur.com/IxdxhV2
I have the ~$800 pro version early in the video. It's an IQAir. I bought it when I bought my house. We were refinishing the hardwood floors and have a small child. My goal was to knock down the VOCs to make the room safe for him prior to move in.
It runs 24/7 in my bedroom now. Huge improvement in sleep quality. I've only had to change one of the filters once for about $100 after 1.5 years of run time.
It runs 24/7 in my bedroom now. Huge improvement in sleep quality. I've only had to change one of the filters once for about $100 after 1.5 years of run time.