Hospital mechanical and plumbing systems are designed to help keep patients, staff, and visitors safe from viruses including the coronavirus.
The Centers for Disease Control and Prevention (CDC) recommends placing a patient who has an infectious disease, such as coronavirus (COVID-19), in an Airborne Infection Isolation (AII) room. An AII room is provided with a minimum of 12 air changes per hour, all of which are exhausted directly to outside. The room is also kept at a negative pressure, meaning that the corridor air is pulled into the room and then exhausted, further protecting the safety of others in the hospital. The CDC recommends the patient should not be placed in any room where room air is recirculated within the building without High Efficiency Particulate Arrestance (HEPA) filtration. Hospital Emergency Room waiting areas, which could have undiagnosed patients, are exhausted directly to outside, minimizing the amount of potentially infectious viruses in the air.
Most of the air in a hospital is conditioned and recirculated and relies on dilution (high air change rates) and filtration for protection. All hospital air handling units are equipped with a final filter with a Minimum Efficiency Reporting Value (MERV) rating of at least MERV 14, which can remove 75 percent of particles 0.3 to 1.0 micron in size, and 95 percent of larger particles. Some hospitals choose to use HEPA filters as the final filters, which remove more than 99.9 percent of these particles.
Clients have asked about the ability of HEPA filters to trap the coronavirus (COVID-19). The coronavirus itself is between 0.06 and 0.14 microns in size. However, a virus does not move around “naked.” Viruses are expelled through droplets of saliva that present themselves as larger particles when they encounter a filter. Based on this information and the CDC recommendations, HEPA filtration can help prevent the spread of the coronavirus.
To successfully use HEPA filtration in an HVAC system, the HEPA filters need to be designed into the HVAC system and air handling unit. Specifically, the filters must be tightly fitted into a specifically designed filter rack with bag in/out capabilities and a blade gel seal type housing. The air handling unit fans need to have enough power to overcome the higher air pressure drop of HEPA filters. A combination of HEPA filtration, supplemented with UV lights, has a better chance of stopping the virus.
This is an excerpt of a piece on FacilitiesNet.
For questions about this piece, contact Suzanne Ferris.