Indoor heating systems may exacerbate flu survival on surfaces and in the air this winter. Forced air, hot water, and infrared heating all significantly reduce relative humidity levels in a home, office, or school by increasing the temperature of already dry air, thus lowering the relative humidity. The research indicates that in more humid environments, the flu virus survival time is markedly decreased on both surfaces and in the air. The best way to raise indoor relative humidity levels is by running a humidifier. When used according to the manufacturer ™s instructions, a humidifier can increase relative humidity above 40 percent.

Relative humidity is a term used to describe the amount of water vapor that exists in the air and a hygrometer is one such device to measure this, said Dr. Ted Myatt, Sc.D., senior scientist at consulting firm Environmental Health and Engineering, Inc. and biological safety officer at the Harvard Institute of Medicine in Massachusetts. It is particularly important to run a humidifier during the winter months when air tends to be colder and drier and when relative humidity levels indoors can reach as low as 20 percent.

Source:  Harvard School of Public Health