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Hey there! Thomas here from Smart Air. Fans do kick the bucket now and then–no fun! We might be able to get a replacement from the factory for you. Send Esther an email: [email protected]
Hi Ian,
I haven’t tested the Samoair, although my strong hunch is that its results would fit the pattern of the four particle counters I’ve systematically tested.
Also, I’m thinking of starting a kickstarter to raise funds to test all the particle counters out there and publish a guide to how accurate they are. I get a lot of questions about particle counters, but there really isn’t a Consumer Reports out there about them. Plus, a lot of people want to know if cheap particle counters are effective.
Carbon?
You’re right! I was reluctant to roll out carbon filters for a long time because I hadn’t seen any real-world tests of commercially available filters, so I spent months and thousands of dollars on testing equipment to do those tests myself.
When I finally got the data, it showed that the carbon filters were removing VOCs (and formaldehyde, which I’ll be writing up soon). After seeing the data, I started shipping carbon filters from Smart Air.
A couple things to remember: carbon mostly gets smells and gases like VOCs, not particulates in general, so you still need a HEPA (in that post, I show a test of what happens when I tried using carbon alone). Those gases are the most common in homes with recent re-modeling, new furniture, or smokers, so I recommend carbon for people in those situations.
Do particle counters measure PM 2.5?
I’m so glad this question came up because I’ve been testing different particle counters lately, and this problem has been on my mind. Many particle counters claim to measure PM 2.5. None do. Not a single one.
Laser particle counters measure a certain particle size and ABOVE. Most laser particle counters measure .5 microns and above. Some go down to .3. Very rarely do I see very expensive machines that claim to get to .1 microns. Government pollution monitors actually sift out particles 2.5 microns and above, then measure the rest of the particles smaller than that.
That means that the measures overlap, but they are not equivalent. When I get time, I’ll write up my tests comparing the government machines to machines that claim to measure PM 2.5. But here’s the takeaway: On average, the particle counters were off by 40 micrograms. 40! That’s twice the WHO limit.
Now, I’m not saying these machines are worthless. They’re incredibly useful, and they are highly correlated in a relative sense with the government machines. The problems come when:
1. Manufacturers call it PM 2.5, which misleads consumers. (I understand why they do this. It makes it much easier to people who don’t want to learn a new system. I’ve made the same mistake in the past!)
2. People interpret the microgram/AQI numbers literally. In reality, my tests found their numbers can be off by more than twice the WHO limit of safe air.
Hey guys,
DJtrekker, that was me! Sorry the fan stopped working!
I’m not an expert on pollution or engineering, so I’ve been learning as I go along. Along the way, I’ve done tests and discovered that carbon can remove VOCs and that, if you turn off your purifier and keep the doors and windows closed, the room air still gets almost as dirty as it was before in just one hour.
Another thing I’ve been learning is that using a filter too long can put more pressure on the fan motor and make it more likely to stop working. But it sounds like in your case that wasn’t the issue. Another hypothesis is that running it 24/7 makes the motor more likely to stop working.
I should be clear about one thing: I have empirical data to support how often to change the Original DIY filter. I do NOT have longevity data on the Cannon yet. As I point out in the the longevity data post, it’s not clear how well the Original DIY data would map onto the Cannon. On the one hand, the Cannon pushes more air, so the HEPA shouldn’t last as long. On the other hand, the Cannon has a pre-filter, which extends the life of the HEPA.
For now, I can only make an educated guess about how often to replace the HEPA on the Cannon. My guess is about three months at 8 hours a day–at most four. In the next few months, I’ll complete a longevity test on the Cannon and we’ll have a more solid empirical answer!
(I should also point out that the big companies give the same estimates for HEPA replacements whether you’re in China or Switzerland. I think it’s necessary to have some data from the ground on China because the air is far worse.)
Hope that helps!
It does come with instructions! You could also order a pre-assembled kit.
But the fun part of the instruction booklet is the other stuff–test data, answers to questions like: do air conditioners bring in dirty outside air? Are particle counters the same as the US Embassy pollution monitors?
Like how much each square inch of HEPA can hold and then just multiply that by the entire surface area of the HEPA?
Hi Brendan, this is Thomas the nerd behind Smart Air. I’ve never heard of a convincing way to calculate how many days of use you could get via a simple calculation or theory alone. Now, I have seen people try, but it seems incredibly “back of the envelope” with a lot of assumptions. Unless I saw that theory backed up with actual data, I think the only way to go about it is to go out and test it in the real world.
And Charlie is on the money: I recommend changing HEPAs every 140 days at 8 hours a day with the Original DIY or approximately 1,000 hours of use.
Yeah! I’d love to see pictures of how the filters are looking. Here’s a picture of the filter from our longevity test at 90 days:
Awesome! So glad to know that’s in the filter and not in your lungs.
I’m actually just about to post results of 90 days of a HEPA longevity test Gus is running. So far, we’re 90 days in, and there’s no noticeable decrease in performance. So my conclusion from the data is that they can get pretty gross looking and still work!
I’ll be posting the test on Particle Counting:
http://particlecounting.tumblr.com/
Thomas here. Good question! I wrote up a description of how different machines measure particle counts:
The government machines actually suck in a cube meter of air and filter out the particles, then shoot carbon 14 beta particles through it. Laser particles measure how much light the particles in the air deflect onto a sensor.
Hi Vincent, Thomas here, the nerd behind Smart Air.
Good question! If you already own one, you could attend and give the new filter to a friend 🙂
Otherwise, shoot me a message, and I’d be happy to let you attend for free.
We’ll be doing fun stuff in addition to the content already up on the website. You’ll get a sneak peek at our longevity tests of how long the filters last, you can test it live with our particle counters, will explain whether pollution masks (what does the data say??), and you can chat with Gus and Anna about any questions you have.
