HALO P HEPA Filter Efficacy in Air Purification
A Recent in-vitro study1. was focused on characterizing the HEPA filter efficacy of the HALO P at removing aerosolized MS2 bacteriophage and replicating an RNA single stranded virus. MS2 is a surrogate virus and has been traditionally used for influenza and now SARS-CoV-2. This study provides insights into the filter’s capability to handle airborne pathogens and pollutants effectively.
Additionally, further testing was performed using various sizes of polystyrene latex microspheres (PSL) to represent a variety of particle sizes. As the HALO P is equipped with an H14 HEPA filter, the filtration has the capability of capturing particles which are both pathogenic and non-pathogenic as small as 0.01 microns in diameter and with an efficiency rate of at least 99.995%. This level of performance is crucial for environments where pathogenic and non-pathogenic particles pose a concern.
During the tests, the HALO P was strategically placed in the ceiling to maximize exposure to circulating air, thereby enhancing the HEPA filter efficacy. Results showed a significant log reduction of 4.13, corresponding to a 99.99% decrease in total colony forming units (CFUs). This confirms the filter’s robust capability in reducing aerosolized pathogens within indoor environments.
Additional independent particulate testing was also performed supporting the fact that the HALO, a ceiling-mounted air purification station, will not only capture particles as small as 0.01 microns in diameter1, but also dramatically reduce the total dose concentration occupants are exposed to. Additionally, being centrally installed in the ceiling is an ideal location to readily remove fine particles, pathogenic and general particulate matter (PM2.5) from our collective breathing zones and improve Ventilation Effectiveness within a room.
Log Reduction
To accurately measure the total log reductions, testing must be performed within a large sealed test chamber to replicate a potentially contaminated room environment and to contain any potential release of aerosols into the surrounding environment. The test chamber used was constructed of 304 stainless with an internal dimension of 9.1ft x9. 1ft x 7ft, or 579 cubic feet.
To achieve consistent results, testing was performed in triplicate series with the HALO P operational. A control run without the HALO on was also performed to generate a baseline and have comparative data. Each test performed ran for a 90-minute period, allowing researchers to monitor the HEPA filter efficacy over time.
General Timeline for Bioaerosol Chamber Testing
As aerosols are inconsistent in size, data was logged to plot the size distribution for MS2 and can be seen in the below graph (y axis represents total particles per cm at 106.)
The goal of this testing was to challenge the HALO P with MS2, a surrogate virus in a worst-case scenario situation and then monitor the log reduction in a consistent manner over a period of time. As seen in the below graph, the HALO P is proven to perform with extreme efficiency showing a steady reduction immediately upon the distribution of MS2 bioaerosols. Within 15 minutes, the HALO was able to achieve a 1 log reduction, equating to over a 90% reduction in viable MS2. Within 45 minutes, the HALO P achieves a 2.5 log reduction equating to a 99% decrease, which is then followed by a continuous reduction with the final sampling at 90 minutes resulting in a net 4.19 log reduction, or 99.99% reduction in viable MS2.
Conclusion of MS2 viable test
While the specific viral dose that is needed to cause infection for SARS-CoV-2 has not been established, it is clear that exposure to viral dose concentration over time is the equation to a successful transmission rate. Because of this equation, mitigating the risk of aerosolized transmission starts with proper ventilation, which encompasses many variables, including proper Air Exchange Rates (ACH), ventilation effectiveness (VEFF), or otherwise known as proper room mixing, and filtration. However, having all these criteria met is extremely challenging. In fact, most facilities, ventilation systems (HVAC) are not equipped to handle such changes required as per ASHRAE’s guidance for reopening buildings and schools.
The HALO P provides an enhanced condition that will meet all criteria, increasing ACH, improving VEFF, adding medical-grade HEPA filtration and providing room level mitigation. This results in a significant reduction in aerosolized pathogens, coupled with an overall improvement in indoor air quality (IAQ) by also reducing bacteria, mold, fungal spores, and general PM 2.5, positioning the HALO P as a permanent solution for infrastructure improvement without the need for extensive modifications.
1. All references, photos, diagrams and charts are derived from the detailed report from Aerosol Research and Engineering titled “Efficacy of the Erlab HALO P Device against Aerosolized MS2 Virus” by Sean McLeod and Jeffrey Trolinger.