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

#301

Post by briandear » Wed, Nov 14, 2018, 4:16 PM UTC

Thlom wrote: post #225

adinobro wrote: post #155

Earlier quoted context omitted.

I know there is mould in my house. We do three things to deal with it: 1. Air Filter (more for pollution but it helps with mould) 2. Dehumidifier which we leave on 24/7 basically for the mould. This is the big one. 3. Wash any mould with vinegar to change the PH after it is wiped off to prevent it from growing back. The mould is still there but the dry air stops it from growing and sporing which is what makes you sti…

A house should be able to dehumidify on it's own by natural air flow. Maybe it's different in more humid areas?

Vastly more different. A place like Houston is going to have “sealed” houses far more frequently than Scottsdale for instance. Sealed meaning the air conditioner will keep the indoor environment manageable. I remember as a kid my grandmother would use that god-forsaken attic fan in lieu of her window-unit air-conditioners and it was pretty much the zenith of misery in a Houston summer.

Natural airflow with the outside at 90% relative humidity isn’t going to do a thing other than make the interior occupants ornery.

The natural airflow design of Apple Park for example, that works incredibly well, but that same design in Houston or New Orleans would be catastrophically ridiculous.

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

#302

Post by nvarsj » Wed, Nov 14, 2018, 4:17 PM UTC

kijin wrote: post #282

nvarsj wrote: post #245

Earlier quoted context omitted.

And open your windows a tad. It's the best way to keep indoor humidity under control during winter. Being in a basement room though, I'm not sure this would have helped.

As someone else mentioned downthread, you need to maintain a rather high temperature (around 25C/77F) in order to reduce the relative humidity enough. This might or might not have been feasible given OP's budget, heating arrangements, and general preference. I for one would not want to live in such a hot room for a whole season even if I could afford to. I keep my room cooler than that even in the summer!

Hmm, my house during winter is usually between 18-20. If I keep the window vents closed (most UK houses have vents above the windows specifically for this reason), I get a lot of condensation around the windows which gets mouldy. Leaving those vents open makes all the difference - no condensation, no mould. Also the house humidity seems to stay under 50% with the vents open.

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

#303

Post by rsync » Wed, Nov 14, 2018, 4:23 PM UTC

peferron wrote: post #130

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…

"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."

Why not have a filtered air ingress ?

That is, instead of sealing the house, why not install an air purifier in a window and have constant fresh air inflow ?

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

#304

Post by jly » Wed, Nov 14, 2018, 4:27 PM UTC

peepopeep wrote: post #22

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 bought one of these earlier this year: https://kaiterra.com/products/laser-egg-2-plus/

They are hard to find and buy in the US, but very popular in China where many cities have major air quality issues. I picked one up on ebay.

Most of these consumer-grade PM2.5 monitors seem to use the same basic laser scatter sensor that measures 0.3um+ particles.

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

#305

Post by stamps » Wed, Nov 14, 2018, 4:32 PM UTC

Elien237 wrote: post #269

I’ve been reading and following these comments now and I’m both impressed and horrified at the same time. As a mechanical engineer, product developer and developing air purifiers specifically for 5,5 years in combination of filter expert till just 6 months ago. I now work in another industry. You can ask me anything and I’ll do my best and be as unbiassed to brands as possible if you want me to. There are a few thing…

Thoughts on Photocatalytic Oxidation?

I have a Vornado's unit and the call it "Silverscreen."

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

#306

Post by rsync » Wed, Nov 14, 2018, 4:34 PM UTC

Scoundreller wrote: post #120

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…

When you can't get house parts, try auto and computer parts. Get some 120mm fans (or an array of 80mm, etc), and some engine air filters. Don't change the filters too often: "It is common, however, for servicing to occur when the filter appears dirty. Engine air filters are designed to actually increase their efficiency by using this initial layer of dust as an added filter layer. Initial filter efficiency is usually…

"Don't change the filters too often"

Thank you for bringing this up ... in industrial settings, filters are "seasoned" for some period before they can be expected to perform at their published ratings.

Many air and water filters' performance continues to rise over their lifetime - the downside being decreased flow rate.

If you are filtering infectious agents with a water filter, I would be reluctant to run them past their lifetime because you could have things living in the filter and filter housing, etc., but if you're just dealing with particles, your filtration should continue rising over time.

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

#307

Post by rsync » Wed, Nov 14, 2018, 4:36 PM UTC

CarVac wrote: post #272

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.

Mcmaster carr[1] is a wonderful commerce website and I am so happy I found them. I buy all of my fittings and hoses and so on from them.

[1] https://www.mcmaster.com/

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

#308

Post by 7000skeletons » Wed, Nov 14, 2018, 4:38 PM UTC

jklein11 wrote: post #283

appleflaxen wrote: post #273

Earlier quoted context omitted.

how do you prove the timing? that it happened at the time of construction and not after?

You get one of the people who did the installation to admit to it. I'm sure you could find someone who has a conscience or doesn't think they are personally at fault who would be willing to own up to it.

I can only speak for UK contractors/companies, but most of these guys will immediately close ranks on you if you try and pull this. The guys at the lower end of the chain won't want to say anything because it could affect their ability to get work at a later date. A lot of them are on temporary contracts, and these companies talk to each other. If they start making noise about these sorts of mistakes, they could well wind up on a blacklist.

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

#309

Post by brixon » Wed, Nov 14, 2018, 4:39 PM UTC

amelius wrote: post #252

peferron wrote: post #130

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…

How do you know you are measuring bad particles, and not good particles (like salts if you live nearby the sea)?

Why would you want to keep salt in the air? It will promote rusting.

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

#310

Post by LeoPanthera » Wed, Nov 14, 2018, 5:01 PM UTC

rsync wrote: post #303

peferron wrote: post #130

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…

"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." Why not have a filtered air ingress…

Most filters and purifiers rely on the air being recycled through the filter multiple times. They only remove some known percentage of particles with each pass.