How Much Should Clean Air Cost? Innovating Affordable Diy Purifiers

THOMAS TALHELM: My story today starts when I was a Fulbright scholar living in Beijing in 2012 and 2013. So I was there doing research when the Airpocalypse hit. Now the Airpocalypse hit-- the AQI-- which, today, in Delhi, is something like maybe 60 or 90-- it was over 500 In Beijing. It was hard to see very far down the street. And at this point I was starting to get worried. Previously, I had worn masks when I was outside. But when the Airpocalypse, I finally started to get really worried about what the air was doing to my health and particularly the air inside my home. So I was starting to get quite worried. And I'll just give a little bit of background. I mean, most people in this room should be familiar with some of the effects of air pollution-- that it has on our health. I can't give it a review of all of that. Trust me that there is a lot of research on that question. But I'll just talk about some of the effects that aren't as well known. So one of the effects that has been studied is that places with higher air pollution have-- among children, children will have lower IQs. It's actually been replicated with animals, as well. Children born in places with high levels of particulate pollution are actually born with smaller head circumferences. And air pollution's also associated with faster cognitive decline among elderly people. And so, when we're thinking about vulnerable populations, a lot of times we think about babies-- we think about young children. We often forget about the elderly. The elderly are more susceptible to air pollution. So if you have grandparents at home, they should also be particularly careful about breathing clean air. Also, rates of heart attacks and strokes among the elderly are higher on days with higher air pollution. I'll show you one study that was done in Boston, in the United States. And so what they did is they just tracked people, elderly people, living in Boston. And then they have their rates of heart attacks-- which is going to be the y-axis, right here. And on the y-axis on the other side, you have PM 2.5. These are particles, small particles, that are in the air. And so what they found is that, on days with higher levels of particulate, people's rates of-- the odds of them getting a heart attack were higher. Now this is the increase in the odds of a heart attack. It doesn't mean that 20% of them where were getting heart attacks. It just means that the odds of the heart attacks were 20% higher. And, as you can see, with each step up in particulate, the odds of getting a heart attack was raised. But one thing I'll point out about this-- the y-axis, here, tops out at about the worst in Boston, which is about 45 micrograms. Now remember, this is in Boston, in the United States. But what happens if we were to have that graph accommodate Delhi? Just let me go over to this one. So, again, I said that that y-axis tops out at about 50. Let's look at-- and 50, 45-- those are the worst days in Boston. Now what if we just change this graph just a little bit to accommodate the average in Delhi-- not the worst days and Delhi, the average in Delhi. That's what that graph would look like. I have no idea what it would do with the heart attacks. We haven't run that study. So, looking at studies like this, it's pretty easy to be scared about what the air pollution is doing to our health. So my next question was, can purifiers protect us? Or are they all just about marketing? So I looked into some of the research. And one problem with some of the research is that a lot of it in the United States focuses on pollen. Now if you look at pollen, compared to other size of particles of things in the air, this is the size of different particles. We go down to very small at, say, 0.01 microns, right here. Pollen is about 10 microns and above. So, when I was looking at these studies showing that, oh, this purifier significantly reduces pollen, that doesn't mean that it can necessarily get things like smog-- these much smaller particles. And we're more concerned about these smaller particles, because they can penetrate deeper into our lungs. And some of the very smallest particles can actually enter into our bloodstream. That's not fantastic when some of those particles include things like lead. So what I was particularly concerned about was to see more data to show that air purifiers could get these small particles. And that's when I saw the blog of a Beijing-based doctor who lives in Beijing-- is from the United States. And he used a machine like this. I've got one over here. This is a laser particle counter. And what this does is it tests for very small particles, down to 0.5 microns. And this was what I needed to answer that question, as to whether purifiers could get these very small particles-- particles that are included in smog, down there. Now what he would do is run these very simple tests. He'd measure how many particles were in the air in his home, and then he would turn on the purifier. And after he turned on the purifier, those numbers would go down. Quite simple. And he ran lots of tests. All of the test results were very similar. After he turned on the purifier, the number of particles in his air would go down. And so, when I saw these tests, I thought-- fantastic, they work. So, problem solved. And so, going from somebody-- all of sudden, I was somebody who was concerned about the air pollution to somebody who just thought all my problems were solved. All I'd have to do is just go out and buy one of those purifiers that he had tested. The only problem is, those things cost over $1,000 US-- about 800,000 rupees. And remember, you'd really have to buy two of these-- one for the bedroom, one for the living room. Add in the cost of the very expensive replacement filters, and soon I'd be spending about 2 million rupees, or about $30,000 US, for about a year's worth of protection. That's quite a bit of money. I was on the Fulbright scholarship, at that time. Now-- or, I'm sorry, I guess that should be $3,000 US. An extra-- extra zero, there. $3,000 US-- still a lot. Now I like to say that the Fulbright is a prestigious fellowship. But the payment is not prestigious. So I certainly didn't have money in my budget to spend $3,000 on clean air. So that got me into the second question, which is, how do filters work? Or, in other words, what's in that box that costs $1,000? So this is, for example, the IQ Air Health Pro. If we look inside that-- I'm going to show you a slightly complicated diagram, but it's actually quite simple. The air comes in the bottom, here. It goes through a coarse prefilter. This is the fan that then pushes more air through a HEPA filter. So, really, the key ingredient of an air purifier is the HEPA filter. It's just a fan that pushes air through a filter. Now these HEPA filters-- they sound fancy. It's a High-Efficiency Particulate Air filter. They sound really fancy, but what are they made out of? They're actually made out of these polyester fibers. So this shirt is probably made out of a very similar fiber. Or many of the shirts that people are wearing today are made out of similar fibers. And they're just randomly arrayed in a square or rectangle shape. And HEPA filters are really what we need, because they capture over 99% of particles above and below 0.3 microns. They get down to very, very small particles. This includes things like PM 2.5 bacteria, viruses, pollen, mold. Basically any sort of particle in the air, this is going to capture it. Now are these HEPAs some new, expensive, patented technology? Actually, they were invented in the 1940s. They were invented as a part of the US's Manhattan Project, where they were concerned about radioactive particles from the atomic bomb. So these things have been around for over 70 years. They are not any company's patent. Anybody can make these. And the material are just synthetic fibers. They're very simple. They're not patented. So there's no reason that these need to cost $1,000. And so, if you think about it, that $1,000 machine is essentially a fan-- and, hey, I've got a fan at home. And then it's a HEPA filter. I was living in China. HEPA filters are manufactured in China. So all I did is I reached out to a HEPA manufacturer in China. I bought one on the internet. And then I strapped it to a fan that I had at home. It's that simple. This is the very first one that I made, in my apartment in Beijing. You can see, it is not fancy. It's not pretty. It's just a fan and a filter. That's it. The fan just pushes air through the filter. And you can see, I didn't even have a strap, on the first one. So I just used a tape measure that a tailor would use to measure your inseam, to strap it all together. So you could see, this wasn't pretty. Now, when I first did this, all I did was I would put this thing in my bedroom, facing me, while I would go to sleep at night. And I took a picture of the filter after every week. So, at week 0, when I was just starting these tests, this is what the filter looked like. And actually, Jay, who helped me start Smart Air here in India, has actually brought some filters. I'm going to show you some filters of Beijing air. But he actually has some HEPA filters that he has used here in Delhi. So this was after a single day of use, this HEPA filter, right there. This is after a week of use in Delhi air. And Jay, correct me if I'm wrong-- this is about a month and a half of air in Delhi. That's pretty scary, right? And we're not talking about outdoor air, here. We're talking about indoor air. So, here in Beijing, things were similar. This is week 0, week 1, 2, 3, 4. And then, after five weeks, that's what the filter looked like. So, at this point, I was really happy. I mean, I was happy because those particles were stuck in a filter and not in my lungs. And I was happy that this showed that this is getting something. But my inner scientist, my inner nerd, was not fully satisfied, because all this really shows is that it's capturing some particles. But how do we know that it's capturing the really small particles? So the next thing I did is I went out and I bought a particle counter-- a laser particle counter. Now my friends made fun of me, because, they said-- I've got a similar one, here. My friends made fund of me, because they said, hey, you're not willing to spend money on air purifiers, but you're going around spending all this money on testing equipment. Guilty as charged. But I was happy to get started. And the reason that I wanted this is I wanted to start doing tests to see whether it's capturing these very small particles. So the very first test that I did is I tested whether the air coming out of the HEPA filter is indeed clean. So, can this HEPA filter remove those very small particles? So I've got a similar version, here. It's just got a fan and a HEPA strapped to it. And then we've got one of those laser particle counters, right here. Hopefully you can see it just a little bit. There's two numbers on here. The number on the right is particles 2.5 microns and above. And so that number right now is at about 70. And this number on the left, here, is particles 0.5 microns and above. These are even smaller, so that's why that number's usually larger. And we're at about 1,300 in the room, here. This is OK. It's actually kind of a nice day out, today. So what I'm going to do is I'm going to turn this fan on, and I'm going to put this particle counter in front of it, and we're going to see how well that does. Let me just put this down real quick. So I'm going to put this in front of the HEPA filter. So, again, this number on the left, there, is at about 1,500. And I'm going to go ahead and turn the fan on. Now HEPA filters should get about 99% of particles 0.3 microns and above. So we should see both of those numbers go down to zero. Now we can see this number on the right, there, is already down to zero, from about 60 or 70. And this number on the left, there, was at about 1,300 particles, and now it's down to zero. So we can see that the number of particles that are getting through this filter are low. So, in other words, the answer to this question-- is the air coming out of the filter clean? The answer is yes. That's pretty easy to do-- pretty simple. The slightly harder thing to do is to answer the question-- is that enough to clean the air in the entire room? So what I did next a was very, very scientific test. I just put the filter pointing at me while I would sleep. And I would put this particle counter on the other side of the room. And then I would turn it on, and I would see what happened to the numbers. And if you look over a longer term, about eight hours, that same trend continues. Now, at this point, I was getting super happy. And, as a true nerd, I love to nerd out about this stuff. And so I just did test after test after test after test. Now, next, I wanted to look at, what about the really small particles? You remember, this gets-- this thing measures 2.5 microns but also 0.5 microns-- those even smaller particles. So, when I looked at those 0.5-micron particles, you can see, this was at about 1,400, right there. In my bedroom in Beijing, on this day, it was about 20,000. That's not good. And, again, I just did test after test after test after test. So, on average, averaging out over multiple room tests, it removed 84% of the 0.5-micron particles and 92% of the 2.5-micron particles. Next I wondered, what if we use a stronger fan? So I went out and I bought every single fan that I could find in China. My only requirement is that it needed a flat front. And so I tested all of these fans. [LAUGH] I turned my home into a testing arena. And after I got done testing all of these fans, there was one fan that came out the winner. And that was this fan, right there. And I called it the Cannon. I called it the Cannon for two reasons. One is that it sort of looks like a cannon. But second is because this thing just really kicked butt. I mean, as soon as you turned it on, the numbers just went down, and it just stayed down. It was amazing. And I've actually got a little video, here, of a live test that I recorded in our office in Beijing. Hopefully that'll play. [INAUDIBLE] So this is me, putting together the Cannon. You can see it's just me strapping a HEPA filter. We've got a sample Cannon right over there. Now this is a 40-minute test. This is shorter than the test that I showed you before. But you can see the numbers start at about a little over 2,000. And you can see the numbers start to go down immediately. This is time-lapsed. This is about 40 minutes elapsed while I'm working in the office, there, in Beijing. So, in about 45 minutes, we've gone down from over 2,000 down to about 300 particles. So that's what it looks like in action. There we go. So the next question I had is, how does that compare to the really expensive filters? And so what we did were directly comparable tests. These were tests in the same room, same particle counter, and the same length of time-- these overnight tests that I was showing you, before. And I tested, again, the two DIYs that I've got. Also the three biggest purifiers on the market in China-- Blue Air, Philips, and the IQ Air. I had-- rich friends let me borrow their expensive machines. And so, as I showed you before, the original got 84% of the smaller particles-- 92% of the larger particles. The Blue Air was a bit better, at 90% and 96%. The Phillips was 93% and 96%. The IQ Air is 91% and 95%. And the Cannon removed just as much particulate as these expensive machines. Now, if I can say, there's one favorite graph that I have on this entire thing. It's to overlay, on top of what you just saw, the cost of these different machines. And I've translated that into rupees. So, again, we've got the effectiveness, here. And I'm just going to lay the price on top of that. Sort of speaks for itself. The one thing that I particularly like-- I mean, obviously the DIY, there, is just ridiculously cheaper than the other ones. But, even among the major brands, it is not the case that the most expensive machine is removing the most particulate from your room. In fact, it's actually the cheapest machine that did the best in these tests. Put another way, for one IQ Air you could fill your home with these originals. Not that I'm recommending that you do that. Or even for the cost of just the replacement filters alone, you could, again, essentially fill your home with these simple filters. So, after I did this, I had several friends who told me that I should not tell anybody about this. I should use this information to get rich. [LAUGH] And I said, you know, I'm a PhD student. I've got a day job. I was happy to put this information out there. So I published how to do it. I published all my test data on a Tumblr-- because Tumblr's not blocked in China-- that I called "particlecounting." I also published this in Chinese. And after I started publishing this stuff, people told me, oh, hey, you know, all that stuff's awesome, but I can't find the right fan. Or, I don't want to build it. Or, which HEPAs are trustworthy? You know, unless you have one of these machines, how do you know that the HEPA that you're getting is actually real? And so I started hosting workshops where I would get people together. We'd build them together. I'd show them how to do it, and we'd test them on the spot, there. Again, with the particle counter. And I also started a website called smartairfilters.com. At this website, we would ship these simple purifiers to people who didn't want to build them themselves. We also have an India website that we launched recently, smartairfilters.com/in. Now that original that I showed you-- the very first machine that I made and tested in my bedroom-- that HEPA filter cost me 110 RMB, or about 1,100 rupees. But, because we order in bulk, we were actually able to get the price lower-- under 1,000 rupees, here in India. So that original runs us 200 RMB in China-- about 3,000 rupees, here in India. The Cannon's a bit more expensive because fan is stronger-- a little over 8,000 rupees. Now, a couple of frequently asked questions about these DIYs-- about how to use them. People often ask, how big of a room do these clean? The small one, obviously, having a smaller fan, is suitable for smaller rooms-- about 15 meters square-- most small to mid-size bedrooms. The Cannon is suitable for larger, usually, say, about 30 meters squared, perhaps up to 40 meters. How loud is it? This is the original and the Cannon compared to all of those expensive purifiers. So, about the same. These are not quiet. Any time you're moving air through a filter, it's going to create noise. But it's roughly comparable. Another question I got was, how often should I change the filter? And I was tempted, because a lot of companies just tell you, oh six months. Or they give you just a really nice-sounding round number. But I've always wondered about those numbers that air-purifier companies give you. Because, where do those numbers come from? If a company that's based in Switzerland is telling you can use it for six months, is that Beijing air? Is that Delhi air? If it lasts six months in Switzerland, is it really going to last six months in Delhi? I'm a bit wary of that. And is that six months at 24 hours a day? Is that eight hours a day? The numbers seem a bit vague to me. So what I wanted to do is test this empirically. And so a friend of mine who helped me start the company-- Gus-- just ran these longevity tests. So, again, we'd have the DIY filter-- particle counter on the other side of the room. And we'd just test this every single day. So a test would look like this. These are the different numbers of particles in Gus's bedroom-- before he turned the filter on, after he turned the filter on, and then after he turned it off again. And so ran this test for 200 days. All of this data is publicly available. You can download it and see exactly how clean the air was in Gus's room-- also what time he went to bed and what time he woke up every morning, if you're curious. And all of these days are available online. So it's just test after test after test after test. All 200 days. And, after all of that test, that's what the HEPA filter looked like-- similar to this filter, here, in Delhi. And what I'm going to show you, here, is the average of each 10 days. So this is the average of the first 10 days. And this is the reductions in the 0.5-micron particles I showed you before-- smaller particles. So this is after 10 days, 20 days, 30 days, 40, 50, 60, 70, 80, 90, 100. Looks like there might be about a 5% drop on average, there. 110, 120, 130, 140-- looks like there's another drop, there-- 150, 160, 170, 180, 190, and then 200. After all of that, we recommend changing it at about 140 days. This is based on about eight hours a day, or about 1,000 hours of usage in total. So that's our recommendation. Now, since this time-- I started Smart Air in 2013. Since this time, I've done a lot of tests-- tested different sorts of purifiers-- brought this particle counter to many places around China. And what I want to share with you, right now, is just the five most important things. If I could condense everything that I've learned from doing all of this test into five lessons for you, these are the five most important things that I've learned while I've been doing this. First, air purifiers work, but there's one thing that you definitely want to avoid-- it's ionizers. If there's one scam that I've seen-- the most widely seen scam that I've ever seen in the air-purifier market-- it's ionizers. You see these a lot in China. You see these ads for these really tiny purifiers that guarantee you-- uh-- in 30 seconds, you can get rid of PM 2.5 and formaldehyde. And it costs 150 RMB, which is super cheap. So a lot of these advertisements really suck people in. They're common on lots of different products. This is our air-conditioner remote, actually, in China. And it's a little bit hard to see, but it's got an ionizer function, right there, on the remote. You might have that on your air conditioning at home, as well. Some cars are actually outfitted with ionizers in the car. So these are quite common. But the problem with-- here's another fan with ionizers. Now the problem with ionizers is-- let me just explain how they work, really quick. Let's say this is my bedroom. And these are bad particles in the air. And I've got an ionizer, right here. So this ionizer will shoot out negative ions into the air. And, as these negative ions are in the air, it makes these particles stick to surfaces in my home. So some of those particles might stick on my bed. They might stick on the wall. They might stick on the floor. Now you might have already conceived of the problem with that. The problem with that is we haven't actually filtered these particles out of the air. We've just made them stick to surfaces in our home. Right? So, when Thomas comes home, let's say Thomas sits down on the bed. And that knocks those particles back up into the air and allows us to breathe them. So the first problem is, touching those surfaces are going to rerelease those particles. Second problem is that heavy amounts of ions will actually create ozone, which is an air pollutant. So, not great. So, if I can condense that down into one point, I would avoid ionizers. Second question I get a lot is, which is cleaner-- indoor air, or outdoor air? The question is important, when you consider sort of lifestyle questions. So this is my friend Kai. He lives in Beijing. And he looks like Van Gogh, as you can see. Now Kai likes to work out, like I do. But he has different options. He could work out indoors-- for example, playing badminton-- or he could work out outdoors-- like playing basketball, here, outside, in Beijing. Now, if Kai wants to protect this health, which one of these should he do? I actually talked with-- part of this question comes from me actually talking to Kai and him saying, well, it doesn't matter, because the air that's indoors comes from outdoors, anyway, right? So it's just the same. Right? So what I did is I went and I tested rooms all around Beijing-- also Shanghai. And none of these rooms have a purifier in there. So I'm just testing unpurified indoor air and outdoor air. And my simple question was, are particle counts lower than outdoor air? These are different locations that I tested around Beijing. This red line, here, is the number of particles that were in outdoor air. So I just made that 100%. And these are different areas around Beijing. These are homes, cafes, Starbucks, my gym-- which I was not happy to see how bad the air was inside my gym. But, as you can see, across the board, indoor air-- even though none of these places are using purifiers-- indoor air is, on average, cleaner than outdoor air. On average, it's between about 50% and 60% of outdoor air, if you do nothing. Now this is important. Because on days where air pollution's bad, it's best to work out indoors. These are pictures, by the way, from the Beijing marathon. I just-- I'm a runner, and the idea of running a marathon in Beijing is just mind-boggling to me. Second, if given the option, I'd rather sit inside in restaurants and cafes, particularly when the air is bad. When you're at home, you're going to want to close your windows and your doors. Obvious exceptions to this are if people are smoking, people are cooking, and if you have recent remodeling or new furniture. If you have that sort of remodeling smell in the air. That's when indoor air could be as bad as outdoor air. Second. People ask me-- or third-- people ask me if they need to run the purifier 24/7. In fact, some companies-- this is Alen Air. On their website they say, we recommend that you run your purifiers 24 hours a day. But that's always struck me as a little bit weird. I mean, what if-- let's say you go to work for eight hours or nine hours a day. Do you really need to keep your purifier running while you're not at home? Always struck me as odd. So what I did is I ran some tests while I was on vacation, to make these as conservative as possible. And I would put the Cannon inside my bedroom and have it turn on, using a timer, for two hours every day. And so here's what that looked like. These are six days. I'm going to show you the data, here. So this is about 24 hours in Beijing. You can see when the Cannon turned on and then when it turned off, using the timer. So my conclusion from that is, it's OK to turn your purifier on when you get home. You don't need to leave it on for-- if you're going to be away from home for eight hours, there's no reason to waste your filter or your energy. It's OK to turn it on when you get home. Second, I had a lot of people email me and ask me if they can turn it off at night. So, for example, somebody emailed me and said, hey, I want to turn it on for a while, to clean the air, and then I'm going to turn it off when I go to bed. Is that OK? And their idea, here, was, well, my doors and windows are closed. So if I get the air to that really clean level, it'll stay at that clean level while I sleep. Right? And particularly the motivation here is that, then you can turn it off, and you don't get the noise from that. Right? So wouldn't that be great? Well, what we can do is we can use those same tests. Now these tests are going to be even more conservative than if you do this test. Because I was on vacation, right? So I don't even have a person-- there's no person in the room. I wasn't opening or closing the doors or windows. All the doors and windows are closed, for this entire test. This is basically the most conservative test you could run using an average person's apartment. And what we can do is we can zoom in, again, on those tests. You remember this first test. And my question here is, what happens after we turn the Cannon off? Right? It's a closed room-- doors, windows all closed. Nobody's at home. So it's even more conservative. What happens? Does the air stay clean? Or do the particle counts go up very quickly after the Cannon is turned off? Here's what happened. Basically immediately. Right? Soon as it turns off, those particle counts start to jump up, almost immediately. And, if we average out over those six test days, within 15 minutes it was back up 50%-- particle counts. Within 45 minutes, back up 75%. And within 80 minutes, we're back up 100%. So, basically, if you turn this off before you go to sleep, your air is going to be-- for the majority of the time that you're sleeping, the air is going to be just as bad as it was before you turned on the purifier. What this shows is that outdoor air is constantly coming into our homes, even if the doors and the windows are closed. Unless you have a particularly well-sealed home-- which it not very common-- then that outdoor air is going to be constantly coming into our home. So, even though we're not aware of it, even though there isn't a breeze coming into our home, that outdoor air is going to get in very quickly. So, basically, the upshot of this is that you don't have to keep it on when you're not at home, but while you are at home you should leave it on. So you should keep it on with you at night. The last thing I'm going to talk about is gases, like VOCs-- these are Volatile Organic Compounds-- and things like formaldehyde. These come from things like paints and new furniture that we have in our home. You can smell it when you enter a room, particularly in a room that's been remodeled recently. OK So companies will sell these carbon filters. Here's what our carbon filter looks like. Ah, thank you. This is it. So a carbon filter like this-- it'll look dark right here, because on the inside, there, is activated carbon, also sometimes called "charcoal"-- "activated charcoal." And what we did is we ran tests of this, using formaldehyde. So we actually-- this being China-- we just ordered formaldehyde from the factory [LAUGH] and got formaldehyde, there. And what we did is we put it in-- so you've got the Cannon, here, with a Cannon filter-- er-- a carbon filter on top of it. We've got a rice cooker, here, that we filled with some water and formaldehyde. Heavy-duty mask, right there, to keep safe. And then what we had is a gas detector that could detect formaldehyde levels and other VOCs. So we ran one condition where it was just a fan. This has just got a fan running in the room. And these are the formaldehyde levels, rising over the course of the test. The second condition that we ran was the fan with that Cannon right there and the carbon filter on top of it. When we ran that test, this is what happened. So this carbon was able to remove these gases like formaldehyde. So carbon-- it targets gases and chemicals. It also removes odors. So if you've got a pet or a younger brother at home, it helps with that. But these are not for general particulate pollution. So, in general, if you're living in Delhi, you need a particulate filter. The carbon is for if you've had remodeling or odors or things like that. So you still need to have the filter. So I recommend these if you've had remodeling, new furniture, if you want to target smells. Finally, that's inside the home. But obviously we all have to go outside, at some point or another, right? So, what about masks? I think this question is particularly important for India, because a lot of people aren't familiar with masks, particularly with the data or the scientific tests on masks. So the first question-- let me just break this down into two simpler questions. Do they block the really small particles, is the first question that I'm going to answer. Fortunately, scientists have done tests on this question. What they've done is use, for example, a diesel generator. So this mimics car exhaust. Stick a pipe on there, stick a mask on the end of that pipe, and then use a particle counter to count how many particles are coming through the mask. So the question here is, can masks get these very small particles? Now obviously, if you put nothing, it's going to block 0% of those particles. When they put a cotton handkerchief on this-- you'll see a lot of people-- I've already seen people in Delhi wearing cotton handkerchiefs. They're not useless, but 28% of these very small particles-- it's not fantastic. Next, they looked at a surgical mask. That actually blocked 80% of particles. Now, a lot of people don't believe this, but the data actually speaks to it in this test and other tests that I'll show you. Surgical masks-- a lot of people think, oh, those don't do anything. But they actually do a decent job. If my choice were nothing or a surgical mask, I would definitely wear a surgical mask. Next, they tested lots of cycling masks. Those were generally in the 80% range. And then finally they looked at simple face masks-- cheap, N95 face masks-- that all got close to 100% of these particles. So we know that they can get the really small particles. But do they actually work, when you wear them? So the second most common thing that I've heard about masks is people say, OK, OK, they can get the really small particles. But when you actually wear them, then all the air is just going to leak in the side, and they don't work. So this question is a lot harder to test. But fortunately people have tested it using what we call a "fit test." So this is that same Beijing doctor that I showed you, before-- Dr. Saint Cyr. I actually begged and begged and begged the 3M company until they allowed me to use their fit-testing machine. This machine costs $10,000 to use. But the reason it costs so much money is because it does this really cool thing-- is-- it can test the air inside the mask, while you're wearing it. So it gets this tube to pull the air out from inside the mask, while you're wearing it. And then this blue tube, right there, is testing the air outside the mask. And so you can say, how many particles are there in the outside air, and how many particles are there inside the mask? So this gives us a measure of how well the mask is working, while we're actually wearing it. Which is a really important question. So these are the results-- my results and Dr. Saint Cyr's results. And you can see, a lot of these simple 3M masks and other masks are capturing over 90% of the particles. And then we can overlay-- this is the cost, here, in RMB-- in Chinese currency. But you get the idea. Again, you get almost no relationship, here, between the cost and effectiveness. So we've got some very cheap 3M masks down there which are capturing over 90% of particles, whereas before I saw this data, I was using a Respro, which cost me about $80 US. So I was spending more and getting less. Now I use these more simple N95 or N99 masks. That's what you're going to want to look for when you're using masks. So this, for example, is one that I've got. I'll be using this while I'm in India. And these are-- these are pretty simple. Some masks that you'll see have these exhaust valves on them, which is this on the side, there. From the tests, that does not actually change the effectiveness, when you're wearing it. All that does is it allows you to breathe a little bit easier. It's a little bit easier to breathe when you've got that on. Now, when you're wearing a mask like this, the most important thing you're going to do is that there's a metal band, right here. You're going to want to make sure that that fits around your nose, so that you've got a good seal. Now we can't all go use this $10,000 machine to do this test. So one quick and easy way to do this, when your-- if don't have this machine, one way that you can do this is, get the mask on. Make sure it fits well. You're going to want to put one of these straps below your ears, one of these straps above your ears, like that. And then what you can do is, make sure it's on right, and then breathe in very deeply, like this. So-- [INHALE] [EXHALE] [INHALE] --like that. And when you're breathing like that, what you're going to want to look for is to see if you can feel any sort of cool air through here or maybe through here. If you can feel a sort of a little breeze through here, that means air is leaking. If you can't feel anything, then, chances are, you've got a pretty good fit, there. So wearing a mask like that is going to protect you from particulate while you're outdoors. And I think people find that those are surprisingly comfortable. Obviously, it's not like breathing without a mask, but it's nicer than breathing in all that pollution. So this is one of the ones that, in China, cost less than $1. And it scored 97% on fit effectiveness. This one is an N99. It's a bit more expensive. That "99" means that it gets 99% of particles 0.3 microns and above. But if you look for an N95 or an N99, that's what you're going to want. 3M makes these masks, but lots of other people also make those masks. You're really just going to want to look for those certifications for the N99 or N95. So the conclusion, there, is, masks are effective. So, if anybody tries to tell you they don't get the small particles or they don't actually work when you wear them, tell them that you've actually seen the data. Get more people wearing masks, hopefully. So thank you for listening. Shoot me an email if you have any questions. You can also email the Smart Air team at smartairfilters@gmail.com. Check out our website. And all of the test data-- and way more test data than you've ever want to see-- is available on my blog, here-- particlecounting.tumblr.com. You can also check us out on Facebook to see any events or workshops that we're going to hold in the future. And thanks again for the U Chicago Center for hosting. Thank you very much.