HEPA filters are a nearly perfect solution for air pollution. They are backed by tons of scientific tests; they’re pretty cheap; they use about as much energy as a lightbulb; they even have documented health benefits. Just about the only remaining problem is that you have to throw out the HEPA filters every few months. So wouldn’t it […]
Category: Filters
Can Activated Carbon Remove Formaldehyde?
In a previous blog post, I wrote about how I tested activated carbon’s effectiveness at filtering out VOCs from cigarette smoke. I also wrote about who actually needs activated carbon (hint: not everyone). One type of VOC that many people are concerned about – especially in China – is “Formaldehyde”. It’s not because Chinese […]
Is a 30 RMB HEPA Reliable?
After I published directions for how to make your own purifier, people asked me: “Which HEPAs should I use? Is this one trustworthy?” That’s the type of question that makes a nerd like me happy because it means we need to get more data. So I ordered HEPAs from every manufacturer I could find, and I […]
Does adding a carbon layer reduce particulate effectiveness?
I recently published tests showing that carbon actually removes VOCs. But adding that carbon layer raises a question: adding carbon means the fan has to power through yet another layer of resistance. Does that make purifier less effective at removing particulates? Methods To test this question, I ran 10 room tests with the Cannon and 10 […]
Does Carbon Really Work?
I wrote early on that my number one concern in China is particulate pollution. It’s on so many people’s minds that nowadays even the guy I buy chuan’r from knows the word “PM 2.5.” HEPAs do an amazing job at removing particulates, but particulates aren’t everything. Gases like volatile organic compounds (VOCs) are so small that they slip through HEPAs. “VOC” […]
HEPA Longevity Test: Day 200
One of the biggest questions when I started doing the DIY was how long the HEPAs last. Rather than just give people a nice-sounding answer, I wanted to see what the data says, so Gus has been dutifully turning on his Original DIY every day in his 12.3m2 Beijing bedroom and tracking how effective it is […]
HEPA Longevity Test: 170 Days
When I started Smart Air, a lot of people asked me how long the HEPAs last. Several people criticized the DIY on Zhihu because they said you’d probably have to change the HEPA so often that it’d end up being more expensive than the expensive brands. At the time, I really wanted to pull out […]
How Long do Smart Air HEPAs last? Longevity Test Day 130
How long do Smart Air HEPAs last? My quest to give a solid empirical answer has now completed 130 days! Gus is still dutifully tracking the effectiveness of the HEPA he’s been using in his bedroom since January (with a trip to the US in the middle), calculating the percent reduction in particulates every night. […]
Types of Filters
Premise: This blog is for people concerned about air pollution. There are many valid reasons people want air purifiers: pet allergies, pollen, and asthma. However, these are not what I’m concerned about while living in China. Here I assess purifiers solely based on whether they can help protect me from particulate air pollution. With that […]
How long do Smart Air HEPAs last? At least 90 days
The most frequent question people ask me these days is: how long does the HEPA last? This question is important because replacement HEPAs are the biggest long-term cost of clean air. IQ Air charges $370 for its filters. So if you have to replace the HEPA every two weeks, the DIY might not save you money in […]