Surgical masks have a lot of bad rep for filtering PM2.5. There’s a fantastic educational poster from Greenpeace that I’ve seen in several places. Here it is: It offers great advice on masks that protect us from PM2.5, soot or wildfire smoke. But then it says this this about surgical masks: “No effect” it […]
Author: Choon Khin
How to Clean and Wash HEPA Filters? Here’s Why You Shouldn’t
Can you wash a HEPA filter? If so, how should you wash or clean a HEPA filter? These questions keep cropping up, as they’re just about the only remaining problem for HEPA filters. HEPA filters are almost perfect: they are backed by tons of scientific tests; they’re pretty cheap; they use about as much energy as […]

Does Rain Clear Smoke and Air Pollution?
There is a common perception that rain will clear smoke and reduce air pollution. Let’s dive into why there is this perception and whether rain truly does clear smoke and improve air quality. 1. Sometimes after it rains in Beijing, the sky is gloriously blue. When that happens, many people like say, “Wow, the rain […]
Smart Air Indoor Air Quality Audit in 3ESpace
Date of audit: 27/05/2017 Audit conducted by: Yap Choon Khin Paddy Robertson Air quality monitor: Dyloc DC1700 Pro AirVisual Node Audit location: 3ESPACE, Beijing Jiaodaokou, Xinhua New Culture Building, 5th floor Air quality measurement outside premises: 115 µg/m3 Corresponding Air Quality Index (outdoors)[1]: 182 Air quality inside premises: 70 µg/m3 Corresponding Air Quality Index (indoors): […]
How Much Pollution Do We Breathe Every Day?
How much pollution do we actually breathe in every day? Are masks or air purifiers more benefiting to our health? Do we really need both? The answer to this comes down to how and where we are spending most of our time every day. There are two possible theories: masks might seem more effective since when […]
Do Air Purifiers Work with the Window Open?
Will my air purifier still work if I have a window open? New test data from Smart Air finds that air purifiers can still meaningfully reduce particulate pollution in a room with a window cracked. Here’s what to know: Obvious Town: Purifiers Most Effective With Windows Closed No one doubts that purifiers are most effective […]

Beijing Air Pollution Drops With Northern Wind, Worsens With Southern Wind
A new analysis of pollution data shows that wind strongly affects Beijing’s PM2.5. The data shows that the best air pollution happens when there are northern winds. Why would northern winds help? North of Beijing is home to sparsely populated Inner Mongolia. Thus, PM2.5 in China’s capital tends to drop when the wind blows from […]
Is There Less Pollution on Higher Floors? How Living in a High Rise Affects Air Pollution
Living on higher floors of tall buildings isolates people from the world. Cars, streets, shaokao vendors—they’re all farther away. So does that mean PM2.5 air pollution is lower on the higher floors of buildings? The Tall Building Pollution Test Tristan from the Smart Air team tested this by taking laser particle counters from floor 1 to […]

New DIY Design Increases CADR 15% – Supplemental Data
Methods Results were identical to my earlier tests of the Original DIY, Blue Air, IQ Air, Xiaomi, and Philips. Anna conducted the overnight tests in her 15m2 Beijing bedroom. Doors and windows were closed during the test (except for occasional opening during the first couple hours before bed—that random variation is one reason I use […]