Blast Mini HEPA filter air purifier in office for protection against COVID coronavirus

How to Choose an Office Air Purifier [Step-by-Step Guide]

Air purifiers in the office are important tools to limit COVID-19 spread. But choosing which air purifier is best for an office can seem complicated. In this article, we take you step-by-step in how to choose the best COVID-19 fighting air purifier for offices. Six Steps to Choosing an Air … Read more

Chandigarh's Smog Tower

Chandigarh Gets Its First Smog Tower, But Does It Work?

Chandigarh is the first planned modern city in India. But with PM2.5 air pollution levels nearly 8 times higher than the WHO recommended limit, the city has turned to a novel solution to help improve its air quality: smog towers. The question is, will Chandigarh’s smog tower help improve air … Read more

Does Activated Carbon Really Work

Does Carbon in Filters Really Work?

Companies sell activated carbon filters (also called “charcoal filters”) to remove chemicals like formaldehyde and benzene, but does carbon really work? The Smart Air lab put real-world carbon filters to the test.

Who Needs Carbon Filters Anyway?

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 kebabs from knows the word “PM2.5.”

China kebab chuanr

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” is a big category, including things like benzene and formaldehyde. VOCs can cause cancer, throat irritation, dizziness, and other not-fun side effects.

VOCs Common Sources
And for homes that have VOCs problems, we’re supposed to use activated carbon filters. But do they actually work?

When I published the instructions for how to build your own purifier, I wasn’t comfortable recommending activated carbon because I hadn’t tested it, and I didn’t want to just trust what the big filter companies say. So this year, I set out on a journey to test whether carbon actually works.

Activated carbon granules

Put to The Test: Does Carbon Really Work?

I soon learned that gas testing is not easy. First off, “harmful gases” is not a natural category. You can buy a particle counter that will detect all particles of a certain size, but there is no detector that will detect all gases. Instead, you need one for each type of gas, and that is not cheap.

In this case, my scientific curiosity cost me $3,542 for this Industrial Scientific Ibrid MX6. It detects VOCs, carbon monoxide, sulfur dioxide, hydrogen sulfide, and nitrogen dioxide. It uses a photo-ionization detector to measure VOCs from 0-2,000 parts per million with a resolution of .1.

Testing Activated Carbon MX6 Ibrid

Next, I needed a source of gas pollution. Interestingly enough, my apartment didn’t have enough VOCs to register on the MX6–nor did 8 other Beijing apartments I tested. (That speaks to whether purifier companies should scare people into thinking that everyone needs carbon.)

Because I didn’t have detectable VOCs in my home, I had to go out and find VOCs to pump into my room. I chose cigarettes because they are known to emit VOCs like benzene and formaldehyde.

In each test, I burned 3 Marlboro cigarettes in an enclosed 3.78 m2 porch. At the same time, I ran the Cannon on high for five tests with a composite carbon filter on the front:

image

I ran four control tests with a fan but no filter. That way the room still has air flow, but no carbon. The cigarettes burned out after about 15 minutes, and I left the fans on for another 30 minutes.

Results: Does Carbon Really Work?

Looking at the Cannon + carbon alone after the cigarette extinguished, the VOCs dropped. Here is the data from one test:

Activated carbon removes VOC gases

But maybe the VOCs would have just dissipated on their own? From there, we can zoom out to include the time the cigarette was burning and the test where we had just a fan (no filter). From there, it becomes clearer that the carbon was removing VOCs above and beyond just having a fan on.

Averaging across all of the tests, the VOCs reached a maximum of about 1 ppm while the carbon was on. Without the carbon, VOCs reached 1.5 ppm.

Activated Carbon VOC Test

After the cigarette burned out, the Cannon cleared the air of VOCs in just over 15 minutes on average. Without carbon, the air still had VOCs after 30 minutes.

Averaging over all of the tests, the carbon removed 38% of VOCs by the time the cigarettes burned out compared to the fan-only condition. The Cannon removed 68% after another 5 minutes and 100% by 20 minutes after the cigarettes burned out.

Carbon VOC Reduction Speed

Bottom Line: Do Carbon Filters Work?

Test data showed that activated carbon filters effectively removed VOC gases compared to just a fan alone. 

Smart Air

Thus, I’ve decided these filters are ready for game time. I’ve started shipping these tested carbon filters via our website and Taobao.

Activated Charcoal Filter

Does Everyone Need Carbon?

Does carbon really work? Yes. But does everyone need carbon? Purifier companies have a financial incentive to convince people to buy carbon filters. They make more money if they can scare people into buying carbon. But does everyone need carbon?

I don’t want to scare people into buying carbon. Why? In most homes, my MX6 detected zero VOCs. I only found VOCs in homes that had an obvious source of pollution such as remodeling or smoke. And in all of the places where the MX6 detected VOCs, I was able to notice a chemical smell. That makes sense, since lots of VOCs have noticeable smells, like benzenetoluene, and formaldehyde.

Now, I don’t want to say that VOCs are never a problem. Photo ionization detectors like the MX6 are not the most sensitive test type out there. I bet I’d pick up small amounts of VOCs if I sent air samples to a laboratory.

However, scientists have used fancier methods and found similar results. For example, scientists in Hong Kong tested homes and found that most non-smoking homes did not have un-safe levels of VOCs. We need more tests like this to be sure.

For now, I will not be using carbon in my home, but I think it is right for people whose homes have:

1. Recent remodeling

2. Recent painting

3. Smoking

4. Odors

5. Nearby sources of gas pollutants (such as living near a factory)

6. Symptoms such as inflammation and asthma

Do I Still Need The HEPA?

Yes. Carbon captures gas pollutants, not particulate pollution. I wouldn’t have even tested this, but Anna accidentally forgot to attach the HEPA and unknowingly ran a regular particulate room test with carbon only.

Activated Carbon Filter Versus Particulate Test

The results weren’t pretty–far below the 95% reduction with the added HEPA. Thus, I do not recommend using carbon only.

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

Read more

Bangalore Gets Its First Smog Tower, But Does It Work?

Although Bangalore is one of India’s fastest-growing cities, this has come at the cost of more air pollution. According to Greenpeace South Asia in 2020, an estimated 12,000 people in Bangalore died due to air pollution. To help improve Bangalore’s air pollution, the city has installed its first smog tower. … Read more

CDC study shows schools that used HEPA filters in the classroom had significantly lower covid-19 infection rates

CDC Study: HEPA Air Purifiers Reduce COVID-19 Spread in Schools

There has been little dispute that HEPA filters are extremely effective at removing virus and COVID-19 sized particles from the air. However, what has been less known is whether or not HEPA filter air purifiers, when used, can actually reduce the transmission of COVID-19. Now, thanks to a study performed … Read more

COVID-19 Delta Variant: Must Know Protection Tips

COVID-19 is spreading like wildfire again with the emergence of the Delta variant. Even after nearly two years and a vaccine, it is clear that vaccination alone is not enough for protection against the Delta variant. In this article, we share some important tips and knowledge for further protection against … Read more

Blast in Hospital

Hospital Air Purifiers for COVID-19 [2021 Guide]

The demand for air purifiers in hospitals has surged due to COVID-19. Hospitals have turned to air purifiers to remove COVID-19 particles and the delta variant from the air. In this article, we tackle what you need to know about choosing an air purifier for a hospital setting.  Can Air … Read more

Best Place To Put Air Purifier in Room

The Best Place To Position Your Air Purifier

“Where should I place my air purifier” is a common question people have when getting an air purifier. Does an air purifier’s position affect its performance? Is it best to put an air purifier next to a wall? This post provides a data-backed answer on how to best place your … Read more

Smart Air is a social enterprise that creates simple, no-nonsense air purifiers and provides free education to protect people’s health from the effects of air pollution. We are proud to be the only certified B-Corp dedicated to fighting air pollution.