Study Finds Ionizers Increase Air Pollution

A peer-reviewed study from the University of Texas finds that ionizers increase air pollution, creating formaldehyde, ozone, and particulate. This data contrasts sharply with claims from air purifier companies that market ionizers as magical machines. One company in China claims that their machine’s negative ions “remove PM2.5 particulate pollution and … Read more

How Wildfires Affect Air Quality in Devastating Ways

It is no surprise that wildfires affect air quality. Pollution from wildfires throughout Australia and California over the years has greatly affected air quality levels. Pictures like the one above show the large amounts of smoke and pollution produced by these wildfires. But how exactly does the smoke from these … Read more

Can Activated Carbon Remove Formaldehyde?

Can activated carbon filters remove formaldehyde and VOCs? Earlier tests from Smart Air found that carbon can reduce VOCs from cigarette smoke. But formaldehyde and VOCs in general are particular concern for many people. We put activated carbon filters to the test by ordering formaldehyde straight from the factory and … Read more

Dyson Pure Cool air Purifier Tower CADR Review

Dyson Pure Cool Air Purifier Review: Shockingly Bad

Dyson’s Pure Cool air purifier looks impressive. However a review of its clean air rating (CADR) reveals this filter does a poor job of providing clean air – the Dyson TP05 Pure Cool’s CADR comes in at just 164m3/hr. That means the Dyson Pure Cool air purifier out as much … Read more

Can Plants Filter Out Formaldehyde and Benzene VOCs?

There’s a popular conception that plants are effective at filtering out VOCs like benzene and formaldehyde, but can plants filter harmful chemicals at meaningful levels? Recent studies have found that that plants have no detectable on removing formaldehyde or other gas pollutants under real-world conditions. Why People Think Plants Can … Read more

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: The Obvious: Air Purifiers Most Effective With Windows Closed No one … Read more

Activated carbon air purifier VOC

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?

Test Method

To test this question, I ran 10 room tests with the Cannon and 10 tests with the Original DIY in the same 15m2 Beijing apartment as my earlier tests without a carbon layer.

 

Dylos particle counter pollution test

 

I measured how much particulate it removed with a Dylos particle counter and compared the particle counts (1) before I turned on the purifier at night and (2) the average of the last four hours before I woke up in the morning.

 

Air purifier test laser particle counter

 

Carbon vs. HEPA Results

With the additional charcoal layer, the Cannon particulate effectiveness dropped 1-2%. Thus, charcoal has a very minor negative effect on the Cannon.

DIY Air purifier test carbon filter HEPA

However, the Original DIY had a harder time powering through the extra layer. Its 0.5 micron effectiveness dropped 19%, and 2.5 micron effectiveness dropped 15%.

DIY purifier activated carbon test

Conclusion: Carbon Tips

For people who need carbon (and that may not be everyone), I would recommend adding the carbon to the Cannon, but I would think twice about adding carbon to the Original. One workaround is to have one Original fan running with a HEPA and another running with a carbon filter.

As always, I’m posting the raw data and more details on the test for fellow nerds below.

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