Please note: During development, Molekule Air Pro was known internally as “Project Sequoia.” The laboratory report from Aerosol Research and Engineering Laboratories reflects this name instead of Molekule Air Pro.
One of the most important features of Molekule Air Pro is the PECO catalyst coated onto the filter. When activated, the catalyst can destroy organic material like VOCs or infectious microbes like viruses and bacteria. Given that viral infection is on a lot of people’s minds these days, the air quality experts at Aerosol Research and Engineering Laboratories (ARE) devised a way to test Air Pro’s ability to decrease virus particles in the air.
The ARE organization is devoted to testing indoor air quality. They follow the Good Laboratory Practices defined by the FDA and have been doing this type of research for more than a decade.
For the testing on Molekule Air Pro, they used their stainless steel bioaerosol testing chamber. This chamber uses the highest possible grade of traditional filtration to stay clean and its steel walls can be easily decontaminated between experiments. There is a variety of equipment connected to the chamber for introduction of test pollutants and sampling of the air inside. It is about 16 cubic meters in volume, which is about the size of a bathroom.
The chamber also has mixing fans inside, which are vital to the proper characterization of any air purifier. These fans serve to distribute the aerosols that have been introduced into the chamber. Without these fans, aerosolized particles could settle to the floor where they cannot be removed by the purifier. Mixing the air with fans prevents any misunderstanding of where the particles have gone after removal.
Raw particle capture
Virus particles are very small, usually somewhere between 20 and 300 nanometers. This is so tiny that 1,000 viruses 100 nanometers in size set end-to-end would be the width of a single human hair. So before testing for the removal of viruses, the team did a test to analyze Air Pro’s performance on inert floating particles.
The team injected different sizes of microplastic particles into the chamber. They allowed Air Pro to run for about fifteen minutes while taking continuous measurements of the concentration of microplastic suspended in the air of the chamber. The results are displayed below.
The straight solid lines across the top of the graph represent control conditions, or when the researchers introduced particles without the device in operation. The dotted lines show the effect of Air Pro. Within five minutes almost 90% of the particles had been removed. After ten minutes it was closer to 99% removal. After fifteen minutes the equipment used to detect the particles could not find any.
Unsurprisingly, the larger 4-micron plastic particles were removed the quickest. The other sizes of particles were also removed efficiently, however. Even particles as small as 0.35 microns (350 nanometers), which is around the size of a large virus, were removed.
Virus species selection
The purpose of these experiments is to figure out how Air Pro might operate on infectious viruses in the real world. The team picked a virus species, MS2 bacteriophage, that would give the best data compared to real-world conditions. This species is not capable of infecting humans and only infects certain types of bacteria making it is easy to work with.
MS2 bacteriophage has a few features that make it an ideal proxy for actual infectious viruses in the real world:
- Small size. MS2 bacteriophage particles are just 27 nanometers, smaller than most virus particles. This means a filter that can deal with MS2 could be better at capturing other, larger viruses.
- Not enveloped. MS2 bacteriophage particles are not enclosed in an envelope, which is an outside layer around some species of virus particle. Viral envelopes have proteins on their surfaces that they use to gain entry into a host cell and without them, they cannot infect. Even small chemical changes to the envelope can prevent successful infection, but MS2 bacteriophage lacks an envelope, making it a little harder to sterilize.
- RNA virus. MS2 bacteriophage is an RNA virus, which is a type of virus that causes many human diseases.
Its small size and lack of envelope make it a little hardier than the average infectious virus, so if Air Pro can remove MS2 bacteriophage it is a good indicator that it can remove other viruses. Then, its status as an RNA virus means it is similar enough to actual human pathogens viruses to be a decent proxy.
After characterizing the particle capture rate of Air Pro and selecting a virus that can be generalized into the real world, the team was ready for the main experiment. This was a little different than the plastic particle capture experiment because viruses can not be meaningfully detected with a particle detector, they have to be transferred to growth plates to check their viability. The team ran four separate trials with Air Pro running at full speed, then one more with Air Pro at a medium speed. The results were as follows:
The y-axis of this graph is displayed in logarithmic format, so each horizontal line represents a tenth of the line before it. This means that “-1.00” corresponds to 90% reduction, “-2.00” corresponds to 99% reduction, “-3.00” to 99.9% reduction, “-4.00” to 99.99% reduction, and so on. After 45 minutes for all four high-speed trials, Air Pro reduced viruses in the air by more than 99.99%. At medium speed, it only took Air Pro another 15 minutes to get to 99.99% reduction.
Controlled and validated testing is important
The techniques used by the team at Aerosol Research and Engineering are informed by standards reached by scientific consensus and following the good laboratory practice regulations set forth by the FDA. You can read their whole report on the experiments described above here.
And you can read more about the performance data that Molekule makes available on our papers page.
It’s important to remember that no air purifier can completely reduce the risk of exposure to viruses. Molekule encourages the use of PPE and medical countermeasures suggested by government authorities.