Air Purifiers – Page 15

Study Finds Air Purifiers Improve Health Markers in Just 48 Hours

2026-04-212018-07-24 by Thomas Talhelm

When we think about harms of air pollution, we often think about the health impacts on infants and the elderly. But does air pollution affect the health of young, healthy people? And if so, can air purifiers help reduce the health impacts of air pollution? Do purifiers have real health …

Consumer Rights Day: CCTV Performed Spot Checks on Multiple FFUs, What They Found Is Shocking

2020-07-152018-03-15 by Joseph Wu

For those who don’t know, an FFU (stands for ‘fan filter unit’) is a type of large size air purifier. Originally created for industrial use, over the past few years FFUs have entered the home market in a big way. They’re a simple and low cost way of getting clean …

This Data Explains Why You Should Never Use Your Purifier’s Auto Mode – Supplemental Data

2020-07-152018-03-09 by Thomas Talhelm

Data and Test Details Test Methods: These tests were identical to my previously published tests, details of which can befound here, here, and here. Original Data: The original data for all 13 tests is available as an Excel file here Average Outdoor PM2.5 During Tests It’s important to note the average outdoor PM2.5 during …

Do Purifiers Depend on the Placebo Effect, or Do They Really Have Health Benefits?

2020-07-152017-12-01 by Thomas Talhelm

I’ve seen people ask if air purifiers depend on the placebo effect or do they actually work. I think this is a good question because we should not confuse the outcomes of (1) objectively reducing pollutants in the air versus (2) health effects. There are two things we know …

Can I Clean or Wash HEPA Filters? – Supplemental Data

2020-07-152017-11-09 by Paddy Robertson

This post contains supplemental data for the post “Can I Clean or Wash HEPA filters?“. It includes detailed information about the testing method, and the original data, open-sourced for all to view. Click here to view the original article Open Data Particle Capture Tests For the particle capture tests, CK …

ALL Purifiers Perform Worse When Air Pollution is Bad: (And How to Fix It)

2021-12-132017-11-09 by Thomas Talhelm

Most air purifier companies hide the fact that outdoor air pollution drastically affects air purifier performance – even when used indoors. When outdoor air pollution is bad, purifiers achieve a smaller percentage reduction. It becomes harder to reach safe levels indoors. Here’s what you can do to ensure you are …

What Eats Airpocalypse for Breakfast and Doesn’t Cost Thousands of Dollars?

2026-03-092017-10-27 by Paddy Robertson

Four years ago, I was coughing through a Beijing winter and wanted some clean air. But all the purifiers I could find cost hundreds of dollars, so I strapped a filter to a fan I had at home and made my first DIY purifier. It wasn’t pretty, but I tested …

New DIY Purifier Design Increases CADR 15%

2020-07-152017-02-20 by Thomas Talhelm

After I made my first DIY purifier, a design magazine called me up to interview me. I said, “You realize this has no design in it, right? It’s just a fan and a filter.” Now I actually have a design improvement! I’m calling it the DIY 1.1. The Problem The …

New DIY Design Increases CADR 15% – Supplemental Data

2020-07-152017-02-17 by Choon Khin

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 It Possible to Lower the Cost of Clean Air Without Sacrificing Effectiveness?

2020-07-152016-05-06 by Thomas Talhelm

A few months after I published my DIY tests, there were already Taobao stores up and running, selling DIYs even cheaper than my 200 RMB. I was intrigued. If we could really lower the cost of clean air, that’s a win!

But we have to be sure these cheaper machines are as effective. So I ordered the cheaper machines, tested them systematically, and found they performed much worse (2).

A New Way to Lower the Cost of Clean Air

But that doesn’t mean there aren’t ways to make HEPAs even more affordable. Recently I tested one way to do that: if we can shave 1 millimeter from the size of the HEPA, we can save 6% on the price. This new size still covers the fan opening, but does it still work as well?

Method

To test this question, my collaborator Anna ran 10 overnight room tests with the 290cm in her Beijing apartment and compared it to my earlier tests of the 30cm HEPA in the same 15m2 room.

Like in my earlier tests, I calculated effectiveness as the percent reduction in particulate from the start of the test to the average of the last four hours. Here’s what one of those tests looks like with the reduction calculation laid out. The blue line is indoor 0.5 micron particles; the red line is outdoor PM2.5

Results

On average, the new 29cm HEPA reduced 0.5 micron particle levels in the room by 86% and 2.5 micron levels by 91%. These results were almost identical to my prior results with the 30mm HEPA.

Conclusion

This new HEPA lets us lower the cost of clean air without sacrificing any effectiveness. Win! We just lowered the price of Smart Air HEPAs from 80 RMB to 75 RMB.

HEPA Cost Comparison

Next I took that price and compared it to the two biggest brands out there, Blue Air and IQ Air. (Also check out the long-run cost comparison .)

Nerd Note on Replication

As a side note, this test is now the third series of room tests I’ve published with the Original DIY (early tests; 200-day longevity test). Add that to Dr. Saint Cyr’s tests, and I’d say that’s a satisfying amount of reproducibility.

For fellow data nerds, I’m posting the original data and more details about the test below.