www . refrigerationandaircon . co . za RACA Journal I July 2023 49
Technical
The latest and most technically advanced laboratory has been designed and built by the EPA ( Homeland Security Research Division ) in the USA to develop and research methods for standardising airborne pathogen efficacy testing . The suggestion has been made that millions of dollars have been spent and largely funded by the United States government , to design a facility to test air cleaning devices for efficacy against SARS- CoV-2 and other airborne pathogens .
The testing which has been conducted will assist the EPA in researching standardised test processes and to better assess the efficacy of aerosol treatment technologies in reducing the transmission of airborne viruses and other diseases in enclosed spaces .
Purpose The purpose of the testing was to develop and research potential methods for standardising airborne pathogen efficacy testing for duct-mounted and in-room air purification devices , in addition to creating a rigorous test environment to evaluate air purification devices and their respective in-room efficacy against airborne pathogens . Results of the study were intended to evidence the potential added benefit that aerosol treatment technologies may have in reducing airborne disease transmission and inform the development of standardised methods for testing .
Method The EPA utilised one of the largest available test chambers , a specifically designed 3 000 cu . ft . biosafety room , to simulate a high turbulence indoor environment with a highly concentrated viral load . Purification devices were duct-mounted to a realworld HVAC fan system operating at 350 cubic feet per minute ( CFM ) to provide a nominal 8 ACH and to simulate real-world air exchange rates .
The EPA used a non-enveloped viral surrogate MS2 , which is 4x-7x smaller that SARS-CoV2 and more resistant than coronaviruses .
Billions of nano-sized viral aerosols were nebulised in sterilised deionised water directly downstream of two floor-mounted mixing fans operating at 1 443 feet per minute ( FPM ). The count median diameter of the aerosolised particles was 46nm ( 0,046 µ m ) at the beginning of each test ( time = 0 minutes ) and increased over the duration of the test to 100nm ( 0.1 µ m ) at the end of 120 minutes .
Aerosol samples were collected at 5ft . high from each end of the room while operating at a humidity level of approximately
www . refrigerationandaircon . co . za RACA Journal I July 2023 49