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

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

#51
post #49

When and for how long should I leave this turned on to be effective in removing dust particles in my small bedroom?

For my air purifier, it generally reports better air quality in less than ten minutes of running at full speed. But, if you're in an area affected by the wildfires, then new particles will also be entering your home / bedroom, so you may want to keep it on low or run it in cycles.

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

#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 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?

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

#56
post #49

When and for how long should I leave this turned on to be effective in removing dust particles in my small bedroom?

Are you ok with white noise while you're sleeping and air flowing in the room? If you're ok with those things, run it while you're at home and sleeping. If you go to work during the day turn it off then, and turn it back on when you get home. It should rapidly clean up the air in a small bedroom.

The only real issue is any continual air flow into the room. There will be a big impact from what kind of air system you have in the greater building. For example, central air without a good filter on that system will make your fan-filter's job a lot harder.

The filters are relatively cheap to replace and will last a long time filtering a small bedroom. I get a solid year out of the filter on my central air system and it's filtering an entire home (non-smoking, no pets). Outside of the small electrical cost or annoyance from having the fan running, there's no reason not to run it very frequently if you derive a benefit. If you don't desperately need purified air for eg allergy purposes and your small bedroom isn't receiving inbound air (eg from a central air system), run it for 20-30 minutes, a few times per day, and that should easily do the job. If that's a hassle, just let it run more often than not.

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

#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 bay area.

My "creation": https://i.imgur.com/jeJfqeW.jpg

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

#58

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 imagine it would help with particulate matter (such as smoke, whether visible or not), but I do not think it would have any effect on gases such as ozone, sulfur dioxide or nitrous oxide.

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

#59

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 don't know about 0.3 micron, but all the different sizes tend to come together. Presence of PM2.5 implies PM0.3

I've got a foobot, I like it. It was benchmarked by some gov't agencies and found to track pretty well.

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

#60
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 (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.

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