Build a Do-It-Yourself Air Purifier for About $40 

It it's on the internet, right? LOL!

It has his name and that he's an MD. What more do you want? They just chose a random room to do this in.

a doctor coat lol

Kris, he seems legit to me! www.uofmhealth.org/profile/280/jeffrey-evans-terrell-md

Pete Miller, Those are mostly internal medicine books. They're real.

I would suggest placing the HPA filter on both sides of the fan.

Demi God I suppose if you care about the tiny leakage, putting it on both sides can't hurt.

+dllexport- well I am planning to replicate this with filters on both sides once I find a cheap squirrel fan. I am growing some button mushrooms or Shiitake mushrooms cultures. Need this to be as sterile as possible.

I was wondering the same thing, maybe he did this as a demonstration example as his measurement tool might not be as effective with the filter on the back side with air leaks.

+Susan Stone Salas yes most likely.

thats fucked up if that is true

Downtime It was fucked up and it is true. I'm heading home for Thanksgiving and I'm making two of these for my Dad because the house is still not safe.

I'd recommend a Roomba

Did you place the filter on the front or on the back? And if on the front, how do you deal with the fans getting dirt? You just clean 'em? How often? Thanks. I've been coughing and hacking for the past month. Allergies me thinks

David Anthony sorry to hear about your mom dude.

the problem with this might be that the air would then be sucked through the edges of the fan on the outake side since it wold produce significant resistance to airflow on the intake. so it is just better to form positive pressure on one side instead of instantly retaking the air it just blew out.

Do the math. Buy a 24" fan, a roll of tape, and a 24" x 24" hepa filter all for $25 where? You can buy decent air purifiers for $50. If you buy a $3 filter it isn't going to filter out anything much you are in danger of breathing in. The doctor know this doesn't cost $25, that is why he said "about" $25. Like he had to guess because he lost his receipt.

The fan motor needs airflow to keep it cool. Thus the filter on the exhaust side.

@@lfrankow Most fans that plug into the wall use induction motors, which are (more or less) constant speed devices. So, if you reduce the load on the fan by decreasing the intake pressure, the motor will not spin faster like a brushed motor (e.g. the one in a vacuum cleaner), but rather will consume less power, and generate less heat. Placing the filter on the intake side does this. There will still be sufficient airflow to cool the motor, especially with the reduced power consumption. Placing it on the exhaust side increases the load on the fan, increasing power consumption and heat. This setup will move more air, but still significantly less than without the filter. The motor will run hotter and have a shorter life. It's a bit counter intuitive, and it's a trade-off. More flow for a shorter fan life, or less flow with the bonus of never needing to clean the fan itself. I've always preferred the intake side, but either will work.

@@BrettonFerguson When this video was made, home air purifiers were much more expensive, and MERV 13+ furnace filters were cheaper. It probably was about $25 at the time, compared to the $800 IQ air unit. You are correct that today it makes much less sense.

It COST YOU NOT COSTED YOU get a 2nd grade education before you post

@@kirkwatstien6979 So following your logic, how much education does it take to see that the comment you replied to is 5 years old? But honestly, it's okay to correct people, but you can do it without being a jerk.

@@kirkwatstien6979 you should get a heart sometimes, something a lot of people are missing these days

@@millenial90 lol underrated reply here. this dude is a true idiot commenting on 5 year old posts

@@millenial90 You can correct someone who says "costed" over and over but they will keep saying "costed". I know from experience.

Good thing the music at the end is both channels...

I spent half the video trying to fix my headphones until the end. Get a stereo recording set up UMICH and quit paying J. Harbaugh so much for mediocrity.

LUL

Same here

I had it on left

Rick, You are so right about the filter placement. The filters should always be the the first elements in the system. Starting with coarsest then finest filtration, if you are using more than one type of filter. Having the filters in front of the fan also means you won't be pulling dirty air across the fan motor and blades. This will result in less, if any, cleaning of the interior of the system. Sealing the filter seat/housing completely is also very important. No leaks that would allow dirty air to sneak by the filter housing. That would defeat the whole purpose. Duck tape it if necessary. In addition I think a box fan is NOT the best choice. I prefer a squirrel cage type fan. Even if you have to build a box around it to seat the filter. Squirrel cage type fans have a much higher flow rate. The more air you move the fast it gets clean or the more air you can clean.

thats how the store kind work, the filter goes on the back, with a pre filter behind the hepa. i get the pre filters at home depot, and just cut them to fit and use a little piece of tape to hold it on the back of the machine. the other filter snaps in place, they can be expensive - but i found that if you clean it every 3 months you can get it to last a year. i use bleach and dish soap water with baking soada, and then rinse in clean water with a little more baking soda - so the bleach kills all the germs and the dish soap gets rid of all the dirt and grease, it comes out nice and white, with a little tint. the soda just dissolves in the water, and stays in the filter, which is good as it absorbs odor. i use the smoke filters, as in the winter, its too cold to go outside, lol.

David Ybarra

David Ybarra Hmm, a "squirrel cage" type fan... I wonder what that is? Excuse me while I go ask a squirrel. Oh, and before I go, I'd just like to thank Dr. Terrell for his very clever idea - - I've always thought "air purifiers" were far too expensive, and the filters as well.

Harry Blowfish A squirrel cage fan is the kind of fan that looks like a snail.

Additionally, he really needs a clipboard.

@@stephanieluigon5192 and a pocket protector. But seriously, I have been using this system for years and it really works in my tiny apartment. I leave the fan on all day on low and you can really tell how fresh the air is when I come home.

💀💀💀💀💀

OMG! lmmfaoooo!!

Rotflol!

Same omfg

@@notreal291 ....Steve?

thanks for the zip tie tip

Congratulations on your new home fire starter kit. The motor does work harder on those Lasko bladed 20" fans when restricted and the amperage climb some. They are not squirrel cage blowers. Massively restricting 20" bladed fans like those Lasko's is a MAJOR fire hazard. That model Lasko is closer to 2,000 CFM and will drop to 50-150 CFM. The guy that posted this video is an idiot. Those motors are AIR cooled and taking away >90% of cooling is a fire ready to happen. Massively reducing the air cooling by dropping air flow 10-20 fold causes the windings to overheat. There were 20,000 House fires from 1990-1998 alone caused by portable fans. @t You need to use a properly designed squirrel cage blower made to handle the static pressure drop. When clogged the amps drop not rise like in bladed fans. I'm an ex Red Badge Nuclear Fire Safety Inspector at San Onofre.

@Manny LOL Radiation is spot on. You posted the dumbest post ever on RU-vid.. He pointed out a potential Fire hazard and referenced 20,000 fires and you say fire hazards are OK if you have many of them. ROTLF. You’re not the sharpest tool in the shed but you are a tool.

@Manny ImBeCiLe ...

@Ilir Cami you do realize that people are trying to create a box fan hepa filter because they dont have $100 spare to spend, dont you? Most people already own a box fan and are hoping to attach a filter to save $90. If you have $100 dollars to spend, then this video isnt for you obviously.

Placebo

@@123idontcareok Cool - you tried it with a particle counter? Do you have a link to your findings? It's weird because there are scientific studies on this that prove a fan and filter removes particulates from the air. Can you provide a scientific study that says it's placebo?

@@123idontcareok - Your life is a placebo.

No problem with the box fans dieing? Just wondering how much stress this would put on the fan? Also how much extra in electricity costs do you pay per month for the two approximately? I am try to figure out if I should do this or buy Honeywell air purifiers. Thanks for any help.🙂

Very informative response. It's much appreciated!!!

***** There isn't a big difference in principle, both are centrifugal and work on fluid dynamic properties. If you throttle your water pump too much, there won't be enough cooling for the pump itself, EVEN THOUGH IT IS USING LESS POWER. In other words, a pump at 1000 watts could be throttled down to 100 watts, but you still have to get rid of 100 watts of heat in the coils of the motor. A box fan is so leaky around the edges, you could completely seal off the back side with plastic and it would use less power but still wouldn't overheat because air leaking in around the front edges. Just say that it is like the cheapest pump ever made. Just look in the HVAC industry, a simple blower (not a ECM blower that compensates for pressure drop!!!!) a SIMPLE blower will draw less amps when the filter becomes clogged. It will have to run longer to get the same heating/cooling effect, but it does so at a lower amperage. For a box fan, it is a simple motor and throttling it will make it draw less amps and it is running 24/7 anyway. Each filter drops about 90% of the dust from the air. If you stack two filters, air flow goes down, power goes down slightly, and you filter at 90% twice, therefore it becomes a 99% filter at about 100-125 cfm on low. And slower air means smaller particles are filtered better through "diffusion" filtering. This means you would filter at over 99%. The little Honeywell is only 95% and about 55 cfm. I have one and it doesn't really do much unless you have a small room...less than 10x10. You said ".do an experiment for me....i want the ppm from a box fan air system....do an air quality test before and after..get back to me and lets open the floor for debate." Isn't that what this video just did? Did you actually watch the video?

Richard Lewis Hi Richard. I'd appreciate it if you could answer a question for me. I got the same fan (Lasko) but it's an older model. I taped the filter to front of the fan and with correct orientation (air flow going same direction as fan). When I do this my fan motor smells like it's burning. I was thinking that maybe there is too much resistance with the filter attached like that. Could that be possible. Does it make more sense to move the filter away about six inches so that the fan blows into it but it's not obstructing it as much? I also think you'd get less blow back and more clean air going into the room.

The Lasko fan is driven by magnetic coil, as far as I can tell. It has 3 settings which alternate between 3 separate resistor circuits to produce 3 separate speeds. When the switch is in one position then the fan will be allowed to draw X amount of current. Since it is the resistance to the voltage and not the air resistance to the fan which controls current, then I don't see how it could possibly be true that adding resistance to one could possibly reduce another. The coil is the motor which exists around the magnets surrounding the axle which holds and spins the fan blades. The coil will use the same amount of power regardless of how fast the fan is spinning simply because the coil is the end of the electrical (or electronic) circuit. Even if you remove the fan land magnets then the coil will still draw all the energy the circuit allows it to draw. Therefor, I don't see how it could consume any more or any less under any circumstances. I am open to explanation. I do have a watt meter somewhere, though it's unlikely that I'll find it anytime soon :-)

***** moving the fan further from the filter, without building a tunnel to contain the air intake, will simply result in the airflow bypassing the fan. Airflow is similar to electricity in that it will always seek out the path of least resistance. A fan filter is big resistor basically. Your fan shouldn't heat up from the any sized filter unless you have fabricated a shroud to prevent in flow from the front corners. You can place your fan flat on the ground and it will simply go from taking the air from the rear to taking the air from around the edges of the face. Which is why someone here mentioned noticing cat hair sticking to those areas on the front. The filter is creating enough resistance to make taking the air from the front and easier option for the fan. Just like a vehicle's radiator fan...you need a shroud to block off those areas around the blade path.

You're welcome! Glad it helped.

That is what I did. You must be an engineer. Where did you put the filter - intake or exhaust?

+buddyroach Damn that is one ugly ass profile pic you have there!

+buddyroach bahahahahahahaha I'm (o-fish-ali) DED!!!!! bwahahaha

+buddyroach Yes, but do you own a lab coat?

lmao I do for gay sex foreplay reasons lol

At least I'm not the only one...

When I read most of these 'ideas" , I wanna kick bitch slap someone!

@@JeanneCulbert Me too!

I hope you've kept hugging 6 years later!

We don't care miss stuck up you and doc are a quink

lol what did he say

Not really a genius move when it's just plain common sense lol

if ur husband thought u were dumb than hes kinda silly

@@supa4ys843 if its common sense why doesnt everyone do it. thtas what makes something common sense, it being common. ive never seen any1 do this

also, I haven't felt the motor but it seems to me that any time you add resistance to a motor then it will heat up. Has anyone been running one of this long term and witnessed any burn outs or fire hazards?

A fans static pressure is the measurement of pressure it can push against. Box fans have extremely low static pressure and are not good at pushing against any force. Assuming your static pressure is high enough, a filter is always going to collect and *hold* more particles if it is on the blowing side. However box fans have very low static pressure therefore they should have it on the intake side.. I would wrap tape around the whole edges of the fan because as you said path of least resistance. You can cover it so it won't have the air holes. If you're worried about too much resistance you can half the resistance by simply placing two filters in a triangle formation on the back of the box fan. This will be shaped like

Why would the fan work harder? How hard an electric motor works is a function of its design and the current and voltage of the electricity supplied to it. The fan's motor doesn't "care" about how much air the fan blades move.

@@The_Komzik How long have you been using this setup? You tape the filter to the intake side? Thanks!

@@Marmocet Current isn't "applied" - it is drawn, and the current a motor draws is dependent on the torque the motor is generating. More mechanical load = more torque = higher current. Most obvious extreme case - completely stall the motor. A stalled motor without any form of current limiting is likely to burn out quickly.

Be careful. It's easier to detect if it's working with the filter on the front, as you can feel the air being blown through the filter, whereas on the back, it can be harder to tell how much air is going through the filter vs. being sucked in the front. Incorrect. Air resistance is related to filter surface area. The better the filter the higher the surface area needs to be to compensate. I would strongly recommend not giving safety advice when you don't know what you're talking about.

yup, had that problem. took another filter on the back to equalize it

I know this is an 11yo comment and you may not even have this account anymore but what merv rating do you use for your pre-filter?

@@shauns5278 I am now using 4" filters with a merv of 13-15. I run my fan constantly and the filter lasts almost a year.

Will you please elaborate on your technique

The older I get it actually traps finer particles.

You replace the filter as needed. They get dirty just the same as using them the regular way. This works great and is similar to what they have done in Hong Kong for filtering their smog. You need a fan that can produce a lot of pressure to filter a lot of air though. This is totally worth doing if you cannot filter your air any other way.

​@Nipha Ahtlantashah I'm just using it at home but I bet it has many uses like that. I saw another video on these that takes it to another level and fixes many of the issues this design has. Instead of using one filter on the front of the fan you can take 2 filters(still 20" high to match fan size but whatever width you want really) and create a triangle in front of the fan with them. Then seal the top and bottom with a piece of carboard cut to size. This is a much better design I think. It gives the fan room to "breathe" and doubles the filter surface area so it is easier for the fan to push air through. Less air is blown back away from the filter and wasted.

Yes, our air purifier clearly shed some material which we could smell when it was first switched on. Then after a day it was fine.

Works the same as a house furnace filter

Has your box fan air purifier held up after a year of use?

@@honkbeforeitstoolate587 it held up, but it was NOT efficient for any type of larger room, and its loud. I also had to get a lesser filter, because the better filters (that filter out more particles) could not circulate the air. So overall, it was a short term solution, not a long term, in my opinion.

@Silly Goose FICK YOU U MICHIGAN PEACE OF SHIT! WHAT THE FUCK ARE YOU DOING IN MY GODDAMN OHIO STATE COMMENT SECTION. See you tommorow at noon (:

@Silly Goose im here what about you? Ill message you back when we win EDIT: touchdown already, fuck good job. You guys missed a extra point so. Ha. In ur face EDIT 2: TOUCHDOWN OSU! Guess who got the extra point mwahahH. EDIT 3: GODDAMN. Thats a 35 yard pass touchdown 6-14 hahHaha EDIT 4: good touchdown MICH i see you i see you. 13-14

@Silly Goose NO FUCK YOPU [e] wd wdwd

@Silly Goose what is that some 4chan crappypasta

December 10

hahahahahahaha!!!

2022: Other than the inflation when looking at the price approximately doubling, if not more than. Thankfully, you can find an old box fan used and restore most likely with some oil to lubricate the bearings and not having to clean much. I'd still clean and decon. Amazingly, I've even found free furnace filters on more than one occasion... though only the one time the 20x20 and the other crunched a little during shipping 16x25x4... so requires some more tape and cardboard. :-) Maybe I can make a video regarding... seems like a plan. Off course... I just checked and the best are MERV11. HHhmmm... maybe time to replace the filter?

Good to know you tried this & it worked. I'm in Eastern Wa & we've had thick smoke for days & I'm thinking of doing this.

Karen Messinger absolutely do it. I wish I could post a day one and now of the filter, it’s awful. There’s been a run on filters here too. It doesn’t need to be 20x20 either. We are using a 20x 25 Merv 12. Good luck, stay safe and keep those lungs safe too!

@glensarahs Sure. You have to filter the air coming in the house. You can either put the fan blowing air out of the house and filter the air in a window drawing air in, or in my case, the filter goes right on the fan blowing in, creating positive pressure, and open a window on the opposite side of the house for the air to exit. the fan creates enough air movement that smoke does not come into the open window.

Asfar as I konw this is the best pirce: bit.ly/2BVvMG1 Its gotta be besst priice! ) ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-kH5APw_SLUU.html

Aka Toledo wolverines.

GearHEAD92 😂

@GearHEAD92 Or people who just don't want to waste money?

The Horror Archivist all of the above

Might help to use a thicker filter and higher MERV rating if you need. You can probably make a few if you hunt around for free or used fans like I noted in my video I made about the one I made... since was surprised so many don't show using a 2" or larger higher MERV rating filter. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-UxGa1_dfGvY.html

FredoFreedom you can’t occasionally get Asthma.

@@YoMama9021 I meant asthma attacks. It reduces frequency of asthma attacks and I need an inhaler less often.

80's? Try the 70's! We slept with windows open no screens, brooms only and no vacuums, hanging clothes outside to dry AND riding in pick up truck beds. Life was AWESOME!

Life expenctancy was less tho

Well the air was not as weaponized then lol

I grew up with bad asthma in the 80's, I'm glad I have the means to live in a place away from diesel fumes now.

The air was cleaner in the 80s as well...

You the real MVP

i searched and only vacuums come up. what do you mean?

Oreck XL air purifier @@garjo8970

Though I see your point, I disagree. If the filter is in front of the fan, it allows the fan more suction to bring in more particulate more forcefully and efficiently as compared to having the filter on the back of the fan. With the filter attached to the back, less particles will be drawn to the fan in the first place.

+Gavin Crane which sucks, I prefer left ear sound, it's more crystal clear.

+AirplaneRandy wrg

Gavin Crane lol thanks for this comment, i thought my headphone crapped out XD

Dass e 🤣

try dangling a filter from each blade, and running the ceiling fan on low speed...

lol I thought it was my headphones, but i could only hear out of the right

+Christopher Brown lol so funny bro.

Your speakers are backwards.

Right ear

Your headphones are on backwards.

Electrostatic charge- but maybe some marketing person will use that as a selling point!

Why

change the filter. i used plastic shipping tape to attach my filter.

+April Harley could you please tell me how is the filter working for you now?? my 4 years son has breathing issues as we have birds nesting in the building and i cant afford an expensive air filter, was thinking to try this out!

+Eng iman I really liked the results. I got a box fan and 20x20x1 filter--most expensive they had. About 40 bucks for both, plus duct tape. I taped the filter to the front and let it run. From 9/29 to 10/9, the filter turned almost black. Daughters headaches and sniffles are gone. Room smelled fresh. Replaced with a cheaper filter, but I'm going to go back to more expensive one. Best investment ever.

April Harley thank u very much for the reply...now i got the motivation to make it.

Do you have the HEPA filter link ? I couldnt find the one that was shown in Video

@@rdyvptnm2014 First note that there are three rating systems: MERV, the national/international standard, MPR, which is 3M's own rating system, and FPR, a system devised by Home Depot. They use different number ranges but can be compared, they all do the same thing. For example, MPR 1500-1900 = FPR 10 = MERV 13. Lots of websites explain these. However, glad you asked because I goofed on the HEPA rating. I thought I had HEPA efficiency, but not quite. I have a Honeywell FPR 10 rating ($19 at HD), which equates to a MERV 13. Only MERV ratings above 16 meet true HEPA standard. The FPR 10/MERV 13 still filters fine dust (as small as 0.3 microns), smoke, and many bacteria and viruses depending on size. Important to me is that the MERV 13 rating (FPR10) filters out lead dust, although I use 3M N100 masks plus other controls. You should just research on your own, too much info to put here. I don't know where the MERV 13 filter came from in the video, but the Honeywell FPR 10 is considered equivalent. You can find furnace filters at various ratings at any hardware or big box store (Lowes, HD, etc.). Here's a HD link. If it opens the same way, there's an FPR 10 and FPR 12 listed first. www.homedepot.com/s/furnace%2520filter?NCNI-5

@@rla1000 Thankyou for detailed explanation. I found this link helpful..www.airfiltersdelivered.com/c/merv-mpr-fpr-ratings

Deathswalk You should have your bachelors now! Congrats on 4 years! 😁

I noticed that also !...LOL

So is this bull? Does this work?

Nia J It works. Just make sure to seal up the edges to the best of your ability. The reading was off because the guy didn't wait for the sensor to stabilize for whatever reason. Just make sure to get a decent fan (because the motor will be your failure point) and to seal the edges. Filter behind the back won't be as effective vs the front

And you'll be pushing dirty air out the back if you put the filter in the front.

Best to use a thicker filter to increase airflow like I did and ideally better than MERV13 though whatever is suitable for your allergens capture to be filtered: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-UxGa1_dfGvY.html

I know right!>? If/when you find a hepa filter that size get 50 quid ready too! shame :(

did u find after all a box fan and hepa filter in the UK?

nope!

I couldn't find a cheap box fan in the UK so I used this air circulator to do the job. Just buy one of the HEPA filters made for the proper units and place it at the intake of the fan. Even though the fan itself is circular I just used a box to house it cut out a square to accomodate the square HEPA filter www.amazon.co.uk/Prem-I-Air-Circulator-black-Ideal-office/dp/B01276V56W/ref=sr_1_sc_2?ie=UTF8&qid=1483902276&sr=8-2-spell&keywords=air+circulatore

UK is almost always cold (?).. Who would start a company of fans and air-conditioner there to lost money? :-o

You two need glasses

No. Either way it only works if you're pushing air through the filter. If the air is not going through the filter, it's not working. You need to increase the surface area of your filter in that case. If the air resistance is too high, neither placement will work. It's entirely possible for a fan to drawn air through it's outtake if the intake is blocked.