What PECO Destroys vs What HEPA Misses in Wildfire Smoke

Wildfire outbreaks inevitably raise questions about the quality of the air that is emitted, and hospitals downwind of wildfires often see increased visits for respiratory problems like asthma, shortness of breath, bronchitis, and chronic obstructive pulmonary disease (COPD).

Smoke from each wildfire is unique, but is always composed of particles and gases. While larger particles are certainly the most visible, tinier particles and gases may travel further from the fire (Black et al., 2017; Kinney, 2008; Prospero et al., 2003; Sapotka, 2005) and can have more significant health effects. Given that fine and ultrafine particles represent the majority of wildfire smoke emissions (Black et al., 2017; Makkonen, 2009; Urbanski et al., 2009) their presence warrants more detailed investigation.

There’s more to wildfire pollution than meets the eye

Smoke from any source of combustion emits two broad categories of pollutants – particulate matter, which may be visible, and non-particulate matter, most of which is composed of invisible gases. Almost any air purifier can filter out particles to a degree, but permanently removing toxic gases like VOCs can be challenging. For the most part, VOCs pass right through HEPA filters. Carbon filters can temporarily capture them, but if heat, humidity, or chemical conditions change, these toxins can emerge from the carbon.

Compared to smoke from fossil fuels, wildfire smoke contains a greater proportion of smaller particles (Black et al., 2017; Verma et al., 2009). In addition, fine particles and chemicals settle out of the air more slowly (Kinney, 2008) than larger particles and as a result, are likely to be of greater concern to populations living further from the source of the wildfire pollution.

In addition, the chemicals produced from wildfire events have shown greater oxidative stress potential and therefore can do more tissue damage than typical, ambient particle pollution from fossil fuel burning (Verma, 2009; Williams, 2013). Most importantly, VOC production from wildfire smoke is higher than in fossil fuel emissions (Mauderly, 2014). These VOCs are known to react with nitrogen compounds both already in the air and emitted by the wildfire to produce ozone (Jaffe, 2012). As a result, populations downwind from wildfires may be at greater risk of exposure to toxic VOCs and ozone (Urbanski et al., 2009), which are far more likely to be absorbed by the lungs and end up in the blood than larger particles which are filtered out by the body’s natural defenses (Kim, 2015).

How Molekule’s PECO technology works on wildfire air pollutants

Molekule Air employs PECO technology to help oxidize and destroy airborne pollutants. The surface of its filter is coated with a proprietary nanocatalyst that is activated by light inside the device. The catalyst mediates a chemical reaction to convert pollutants passing through the PECO filter into safe elements of the atmosphere like carbon dioxide and water.

The traditional approach to air cleaning has been to use high-powered fans to pass large volumes of air through a collecting filter such as a HEPA-rated filter. This older approach is designed to mechanically strain floating matter from the air and store it on the filter. PECO reinvents air cleaning by destroying pollutants. Dealing with air pollution on the chemical level is specifically intended to permanently remove VOCs and ozone from the air.

Molekule Air also contains two filters readily capable of capturing larger particles resulting from smoke. Together, these capabilities allow Molekule Air to remove a wide range of pollutants from the air, across various chemical characteristics and sizes.

Molekule air purifier vs VOCs present in wildfire smoke

In order to confirm the viability of PECO technology, Molekule’s Research and Development (R&D) team ran tests on many volatile organic compounds (VOCs) often found in wildfire air pollution and ozone known to result from wildfire smoke in a room-sized chamber (G/BT 18801, 2015) containing a Molekule Air device.

Molekule air purifier testing in large chamber

Interior of the 27 m3 Environmental Test Chamber with Molekule Air device and PID data collection system installed.

The Molekule R&D team selected a suite of different VOCs known to be direct or indirect (Urbanski et al., 2009) products of wildfire smoke. Each one chosen is known to be emitted from wildfire smoke at a rate of at least 0.2 grams per kilogram of burnt plant matter.* In addition, the team included two additional compounds to further demonstrate the VOC reduction ability of PECO technology- ethyl acetate and acetyl acetone to represent the acetate and ketone families of organic compounds, respectively.

Samples were analyzed using various methods to illustrate the levels of chemical degradation. Since the gases selected have different properties, it is necessary to use multiple instruments to detect their presence or absence. Gas Chromatography/ Mass Spectrometry (GCMS) and High Performance Liquid Chromatography (HPLC) were used to test for the presence of VOCs introduced into the chamber. In addition, the team placed a photoionization detector (PID) in the chamber to measure an approximation of total VOC content.

Prior to testing, the chamber was purged with zero air and a Molekule Air unit was placed in the middle. VOCs were introduced as the unit ran on its highest speed. Measurements were taken with GCMS after fifteen minutes to test rapid elimination, one hour for longer term, and eighteen hours to measure what might happen with nearly a full day of running the unit.

Injecting VOCs into testing chamber for Molekule

Injection process for volatile contaminants, demonstrating microsyringe, injection port, and gas purge valve for zero gas purge (certified < 0.1 ppm total hydrocarbons)

The results below show that all of the VOCs were significantly reduced over time, and some even beyond the ability of GCMS to detect.

Percentage Remaining Over Time in a 27 m3 Chamber
Compound name 0 h 15 min 1 h 18 h
Compounds from Wildfire Smoke
Acetic acid 100% 53% 36% 7%
Benzene 100% 30% 29% 22%
Toluene 100% 22% 16% 5%
o-xylene 100% 36% 10% 0%
m,p-xylene 100% 23% 11% 1%
Ethyl benzene 100% 35% 13% 1%
Additional Test Compounds
Ethyl acetate 100% 30% 29% 19%
Acetyl acetone 100% 36% 7% 0%
Total VOC Concentration
Toluene equivalent 100% 21% 13% 7%

Two of the wildfire VOCs, formaldehyde and isobutyraldehyde, were tested using HPLC as the optimal method. These challenge pollutants were introduced to the large chamber and sampled after 4 hours and 20 hours of Molekule Air running at its top speed.

Percentage Remaining Over Time in a 27 m3 Chamber
Compound name 0 h 4 h 20 h
Compounds from Wildfire Smoke
Formaldehyde 100% 65% 0%
Isobutyraldehyde 100% 22% 0%

Similar to the compounds tested with GCMS, these two VOCs also disappeared beyond the ability for the HPLC method to detect.

Molekule air purifier VOCs present in wildfire smoke – smaller chamber

We also tested in a smaller chamber to demonstrate the ability of PECO to destroy VOCs in the immediate area around the device. The test also used GCMS to measure the presence of each individual VOC.

Percentage Remaining Over Time in a 0.6 m3 Chamber by PECO
Compound name 0 h 15 min 1 h 18 h
Compounds from Wildfire Smoke
Acetic acid 100% 1% 1% 0%
Benzene 100% 0% 0% 0%
Toluene 100% 0% 0% 0%
Hexane 100% 0% 0% 0%
o-xylene 100% 2% 0% 0%
p-xylene 100% 2% 0% 0%
Ethyl benzene 100% 2% 0% 0%
Furan 100% 13% 2% 0%
2-methylfuran 100% 0% 0% 0%
2-butanone 100% 0% 0% 0%
Isopropyl alcohol 100% 1% 0% 0%
Additional Test Compounds
Ethyl acetate 100% 0% 0% 0%
Acetyl acetone 100% 0% 0% 0%

In these results, it’s clear that the air directly exiting the Molekule device is very clean, with some VOCs being eliminated within the first 15 minutes.

Molekule air purifier vs ozone

VOCs are not the only air pollutants that result from wildfire smoke. Another toxic substance resulting from the interaction of VOCs and nitrogen oxides in the air is ozone. Because of this, the Molekule R&D team also tested Molekule Air’s ability to decompose ozone in a room-sized chamber.

In order to test this pollutant, an ozone generator was activated in the chamber and an ozone probe was used to measure the change in ozone concentration. The ozone generator was allowed to run for 3 minutes to drive the concentration of ozone up to around 0.2 ppm, which the EPA considers to be “very unhealthy.” The probe then measured the concentrations as the ozone diffused throughout the testing chamber. Ambient ozone concentrations in the lab were reported to be 0.02 – 0.03 ppm.

The team ran three tests:

  • Just the ozone generator alone to measure the natural decay of this reactive substance (blue line below)
  • Molekule Air without an active filter and just the fan running at the highest speed (orange line below)
  • Molekule Air with an active filter running at the highest speed (gray line below)
Graph showing ozone degradation by Molekule

Graph depicts ozone degradation by Molekule Air (MH1) purifier over 1 hour in a room size of 27 m3.

These results show that Molekule Air is capable of handling ozone. Actively running the filter shows a rapid decline in ozone concentrations.

Natural Decay

When simulating this real-world room (G/BT 18801, 2015), the team used a 27 cubic meter chamber (pictured above). This chamber was first purged with a tank of zero air calibrated to contain less than 0.1 ppm in total hydrocarbons, which ensures that the detection instruments are detecting the substances injected for testing purposes and not contaminants from outside the chamber. The VOCs were introduced one by one in concentrations meant to achieve 1 ppm after complete evaporation. In order to establish a baseline and control measure for how these particular VOCs settle and condense in the chamber, they were first added to the chamber alone, prior to introducing Molekule Air and allowed to settle for 16 hours to test their natural rate of degradation.

Control: Percentage Remaining Over Time in a 27 m3 Chamber Without Unit
Compound name 0 h 16 h
Compounds from Wildfire Smoke
Acetic acid 100% 65%
Benzene 100% 82%
Toluene 100% 88%
Hexane 100% 76%
o-Xylene 100% 74%
m,p-Xylene 100% 88%
Ethyl benzene 100% 75%
Additional Test Compounds
Ethyl Acetate 100% 83%
Acetylacetone 100% 71%
Total VOC Concentration
Toluene equivalent 100% 81%

PECO destroys while HEPA only captures

Though there are many components of wildfire smoke, Molekule Air is well-equipped to address them. Molekule is able to destroy a myriad of VOCs and ozone while still being able to tackle polluting particles, unlike traditional HEPA which can only capture them.

For more information on how to stay safe during wildfire season, check out our blog posts on how wildfire smoke is dangerous to your health, how air purifiers can help with wildfire smoke, and if N95 masks are the best solution for wildfire smoke.


References

Black, C., Tesfaigzi, Y., Bassein, J.A., Miller, L.A., 2017. Wildfire smoke exposure and human health: Significant gaps in research for a growing public health issue. Environ. Toxicol. Pharmacol, 55, 186-195 .

G/BT 18801-2015. National Standard Of The People’s Republic Of China – Air Cleaner

Jaffe, D.A., Wigder, N.L., 2012. Ozone production from wildfires: A Critical Review. Atmos. Environ. 51, 1–10.

Kim, K., Kabir, E., Kabir, S., 2015. A review on the human health impact of airborne particulate matter. Environment International. 74, 136-143.

Kinney, P.L., 2008. Climate change, air quality, and human health. Am. J. Prev. Med. 35, 459–467.

Makkonen, U., Hellén, H., Anttila, P., Ferm, M., 2009. Size distribution and chemical composition of airborne particles in south-eastern Finland during different seasons and wildfire episodes in 2006. Science of the Total environment. 408. 644-51.

Mauderly, J.L.,Barrett,E.G.,Day,K.C.,Gigliotti,a.P.,McDonald,J.D.,Harrod,K.S.,Lund, a.K., Reed, M.D., Seagrave, J.C., Campen, M.J., Seilkop, S.K., 2014. The National Environmental Respiratory Center (NERC) experiment in multi-pollutant air quality health research: II. Comparison of responses to diesel and gasoline engine exhausts, hardwood smoke and simulated downwind coal emissions. Inhal. Toxicol. 26, 651–667.

Prospero JM, Lamb PJ, 2003. African droughts and dust transport to the Caribbean: climate change implications. Science. 302, 1024 –1027.

Sapotka, A., Symons, J.M., Jan Kleissl, J., Wang, L., Parlange, M., Ondov, J., Breysse, P., Diette, G., Eggleston, P., Buckley, T., 2005. Impact of the 2002 Canadian Forest Fires on Particulate Matter Air Quality in Baltimore City. Environ Sci Technol. 39, 24-32.

Urbanski, S.P., Hao, W. M., Baker, S., 2009. Chemical Composition of Wildland Fire Emissions. In: Bytnerowicz, Andrzej; Arbaugh, Michael; Andersen, Christian; Riebau, Allen 2009. Wildland Fires and Air Pollution. Developments in Environmental Science 8. Amsterdam, The Netherlands: Elsevier. 79-108

Verma, V., Polidori, A., Schauer, J., Shafer, M., Cassee, F., and Sioutas, C., 2008. Physicochemical and Toxicological Profiles of Particulate Matter in Los Angeles during the October 2007 Southern California Wildfires. Environ Sci Technol. 43, 954-960.

Williams, K.M., Franzi, L.M., Last, J.A., 2013. Cell-specific oxidative stress and cytotoxicity after wildfire coarse particulate matter instillation into mouse lung. Toxicol. Appl. Pharmacol. 266, 48–55.

*Please note some extremely flammable compounds were left out of the final testing as it is assumed they would completely burn up during the wildfire

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