After two years of infestation, the COVID-19 pandemic is far from over. According to the WHO's weekly report, as of May 15, there were more than 518 million confirmed cases globally and more than 6 million deaths. At the beginning of the COVID-19 pandemic, the WHO stated that it was not airborne. Instead, the agency stressed the importance of hand hygiene and social distancing. It took WHO almost two years to acknowledge that the virus could travel on tiny particles called aerosols that can spread widely and linger in the air and clearly state that it is airborne.

Several vaccines, rapid test kits, and antiviral drugs are FDA-approved or under emergency use authorizations to fight the coronavirus disease. In addition to medical/biological approaches, some physical/engineering measures may be just as important and effective. The fight against COVID-19 can follow the hierarchy of control of occupational hygiene: source control, pathway control, and receptor control. Various face masks ranging from N95, surgical masks, cloth masks, or barrier face coverings have been used to protect the person or the environment. High protection devices, such as N95, are always at the expense of high air resistance. The barrier face coverings usually pose the least air resistance but the lowest protection. The face seal fit is as crucial as the filtration efficiency of the filter media. It has been found that properly wearing a respirator takes some training and education.

Therefore, the positive pressure powered-air purifying respirator (PAPR) is recommended for healthy people. However, the conventional PAPR is clumsy, especially for healthcare workers. The newly developed BR-PAPR (Breath Response PAPR) is highly recommended to replace the conventional PAPR because of its lightweight and comfort. The personal exhaled breath aerosol receiver (PEBAR) is recommended for confirmed or asymptomatic cases. 
 

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