Building Immune Systems in Restaurants

Low humidity decreases protection, increases inflammation, and slows down tissue repair. There is a lot of data to support these theories. Studies have shown that “Dry air exposure of mice impairs epithelial cell repair in the lung after influenza virus infection” (14) . In Wuhan, China, researchers confirmed that respiratory infection was enhanced during unusually cold and low humidity conditions. In a four-year study monitoring infection rates with varied humidity levels, the infection rates were lowest when indoor relative humidity was between 40-60% for respiratory and gastrointestinal infections. All these studies support the ASHRAE chart below, “Optimal RH Level for Health,” which shows the decrease in adverse health effects in the 40-60% relative humidity range (13) .

Figure 9. Optimal RH Level for Health, ASHRAE 1985 (8, 13)

Consistent with the above findings, it is suggested that humidity levels in the space should be maintained at levels consistent with current design levels (50 to 60% RH) (12,13,14) . To provide preventative and responsive measures, it may be determined for space temperatures to shift to be warmer or colder to help maintain the space relative humidity within these goal boundaries.

A strategy to allow higher or lower space temperatures could allow other beneficial changes to the HVAC system. For example, higher quality filtration and the associated increase in static pressures would force a lower airflow in an existing system. The change in space design temperatures would allow these lower airflows.

Building Immune Systems in Restaurants | July 2020