Wildfire outbreaks inevitably raise questions about air quality, 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 detailed investigation.
So, in order to confirm PECO technology’s effectiveness in handling these pollutants, 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. The testing showed Molekule Air destroying these VOCs.
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. 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 show 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).
Molekule Air vs VOCs present in wildfire smoke
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.
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 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 VOCs in wildfire smoke
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.
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
