Build a do-it-yourself home air purifier for about $25 • Hacker News Board

Re: Build a do-it-yourself home air purifier for about $25

#81

Post by jchrisa » Wed, Nov 14, 2018, 1:16 AM UTC

LeoPanthera wrote: post #57

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…

The future is already here, it's just not evenly distributed.

Re: Build a do-it-yourself home air purifier for about $25

#82

Post by abalone » Wed, Nov 14, 2018, 1:19 AM UTC

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.

Re: Build a do-it-yourself home air purifier for about $25

#83

Post by ocdtrekkie » Wed, Nov 14, 2018, 1:23 AM UTC

Insanely simple idea when you think about it. Side perk: My furnace uses the same size filters, so it won't even be a hassle to stock ones that fit a box fan.

Re: Build a do-it-yourself home air purifier for about $25

#84

Post by csours » Wed, Nov 14, 2018, 1:27 AM UTC

blattimwind wrote: post #70

ed_balls wrote: post #52

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 gr…

> I wonder if you'd put cotton wool, how effective it would be. Not very. Wet wool is better, but only as long as its wet and clean. > XIAOMI Mi Air Purifier 2 straight from China Interesting question. Does the removal of particulates offset the health impact of its cheap plastics?

Does anyone know what the actual smell of "chinesium" comes from? The smell of artificial rubber products from china, like remelt and cancer.

Re: Build a do-it-yourself home air purifier for about $25

#85

Post by benbojangles » Wed, Nov 14, 2018, 1:29 AM UTC

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.

Re: Build a do-it-yourself home air purifier for about $25

#86

Post by asdff » Wed, Nov 14, 2018, 1:29 AM UTC

cheunste wrote: post #26

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.

Skip the pi, just grab an outlet timer from the hardware store for a couple bucks.

Re: Build a do-it-yourself home air purifier for about $25

#87

Post by mynameishere » Wed, Nov 14, 2018, 1:30 AM UTC

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.

Re: Build a do-it-yourself home air purifier for about $25

#88

Post by user764743 » Wed, Nov 14, 2018, 1:35 AM UTC

You could also buy a plant.

Re: Build a do-it-yourself home air purifier for about $25

#89

Post by akeck » Wed, Nov 14, 2018, 1:37 AM UTC

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.

Re: Build a do-it-yourself home air purifier for about $25

#90

Post by apo » Wed, Nov 14, 2018, 1:38 AM UTC

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?