Is that little fan really effective? I just duck taped a furnace filter to a 20 dollar box fan. No 3d printer needed.
Just did this recently actually here's a pic https://mobile.twitter.com/jonathanfly/status/12155378275654...
A small DIY air purifier
31–40 of 178 posts
Re: A small DIY air purifier
#32Air quality test before and after or it doesn't work. I am very suspicious with regards to air purifiers. Have you ever seen real HEPA filter? It is thick and it is quite difficult to push air through it. I can't imagine small PC fan that is designed to push air through UNOBSTRUCTED space will make any significant flow of air. I have spent some time with the guys who build PCs and who know great deal about fans and o…
> Because they are designed to be quiet and still provide good flow of air they produce almost no pressure differential to speak of and the flow can be halved by a wire mesh that is a bit too dense There are high static pressure fans which address this problem, specifically designed to work with pressure differential, usually used to blow air through radiators for water cooling. The fan linked in the github page (Noc…
> it provides a static pressure of 7.63 mmH2O
If anyone else is wondering, that's about 0.8 mbar (roughly 8 ten-thousands of an atmosphere), or 80 Pa of over-pressure.
To put this into perspective, my local atmospheric pressure varied about 2000 Pa in the last 48h due to weather changes.
Re: A small DIY air purifier
#33Do air purifiers really work? I always have impression they're just sham, or at least placebo.
Yes they do. But you need a sufficiently powerful one to be able to circulate the air in the room enough times per hour, more that the circulation that occurs through the doors, windows and even walls.
Eco-rated houses have a circulation of about 2-3 times per hour. Older houses that are well insulated are about 5-6 times per hour. The purifier needs to be powerfull enough to spin the entire air volume couple of times faster than the natural circulation.
If your windows and doors leak too much, or if you open them too much, or if you burn oil / light up cigars too much and produce smoke then it might be pointless.
I live in one of the cities where the pollution is regularly at the top 10 in the world, and the unit I have is able to reduce the pollution inside to a level that is 5-6 times lower than outside if it runs constantly in a mode that is like 30% of the power. It could do better, but it would be too loud for me.
Re: A small DIY air purifier
#34I would say that there are electronic schemes and plans to build DIY ion air cleaners. They works nice to remove dust or tabacoo from air. Also, ozone air purifier make wonders to keep at bay smells and fats (wonderful to have on the kitchen), and kills bacterias, spores and fungus.
Ozone is harmful.
It also smells bad too
Re: A small DIY air purifier
#35Pollution sensors for indoor use that can be plug via USB to the mobile phone are really cheap, you can find laser ones like Nova SDS for $17 and some that are not so precise come even cheaper than that.
So unless the author buys a real PM2.5 sensor and does a test in a true room and not a box of the size of a Desktop PC, with the sensor on the opposite side of the room, and proves that the pollution drops to below 8micrograms/m3, in a reasonable time frame, than we can say that it is working.
Until than we can only say that the purifier is only able to purify a desktop PC.
Re: A small DIY air purifier
#36if you don't mind a noise you could buy a 2nd hand vacuum cleaner with a built-in hepa or water filter (ideally also with adjustable speed to make it less noisy) and just let it run without a hose, sucking the air and pushing it through the filter...
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Re: A small DIY air purifier
#37Static pressure is important as well as airflow! Some info:
https://www.engineersedge.com/filtration/hepa_filter_pressur...
Re: A small DIY air purifier
#38Air quality test before and after or it doesn't work. I am very suspicious with regards to air purifiers. Have you ever seen real HEPA filter? It is thick and it is quite difficult to push air through it. I can't imagine small PC fan that is designed to push air through UNOBSTRUCTED space will make any significant flow of air. I have spent some time with the guys who build PCs and who know great deal about fans and o…
> Because they are designed to be quiet and still provide good flow of air they produce almost no pressure differential to speak of and the flow can be halved by a wire mesh that is a bit too dense There are high static pressure fans which address this problem, specifically designed to work with pressure differential, usually used to blow air through radiators for water cooling. The fan linked in the github page (Noc…
https://noctua.at/en/nf-f12-pwm/specification
Static pressure 2,61 mm H₂O <-- according to the vendor
Re: A small DIY air purifier
#39Air quality test before and after or it doesn't work. I am very suspicious with regards to air purifiers. Have you ever seen real HEPA filter? It is thick and it is quite difficult to push air through it. I can't imagine small PC fan that is designed to push air through UNOBSTRUCTED space will make any significant flow of air. I have spent some time with the guys who build PCs and who know great deal about fans and o…
>The larger the surface of the filter the easier time the fan will have to push the air through it and more efficient it will be. This is quite true. Assuming the media in your particle filter is of sufficient quality, the most important metric to look at is the aggregate surface area. The larger the surface area, the more air you will be able to move through it and the more particulate matter it will hold before req…
The quality of the filter is important if you want to remove very fine particles.
Even good filters do not typically remove all particles, only particles above certain size. If you have cheap filter it may not even capture a portion of the particles you are interested to remove, it may remove none no matter how many times you cycle the air.
Re: A small DIY air purifier
#40Air quality test before and after or it doesn't work. I am very suspicious with regards to air purifiers. Have you ever seen real HEPA filter? It is thick and it is quite difficult to push air through it. I can't imagine small PC fan that is designed to push air through UNOBSTRUCTED space will make any significant flow of air. I have spent some time with the guys who build PCs and who know great deal about fans and o…
> Because they are designed to be quiet and still provide good flow of air they produce almost no pressure differential to speak of and the flow can be halved by a wire mesh that is a bit too dense There are high static pressure fans which address this problem, specifically designed to work with pressure differential, usually used to blow air through radiators for water cooling. The fan linked in the github page (Noc…
> it provides a static pressure of 7.63 mmH2O, which is very high.
Actually, it depends on the specific HEPA filter if that is enough or not. If it's not enough, the air will find the path of less resistance and circulate in and out thru the fan blades, but not thru the filter.
For some HEPA filters you can find specs. These (https://www.airclean.co.uk/download/4724) are spec to 250 Pa which would be about 25 mm H2O if I am correct.