Humidifiers may help in reducing flu virus

A newly-released scientific white paper suggests humidifiers may play an important role in reducing the survival of the flu virus on both surfaces and in the air. The research suggests that homes kept at 40-60 percent relative humidity are likely to have fewer flu viruses lingering in the air and on commonly-touched surfaces like sink faucets, door handles, and countertops. By running a humidifier to raise indoor relative humidity levels, the research indicates that flu virus survival in the air and on surfaces can be drastically reduced in households, schools and offices.

Millions of flu particles can linger in the air and on the surfaces we touch day in and day out, from computer keyboards and TV remotes to the kitchen sink or refrigerator door handle. With flu top of mind this year, there has been increased interest by the scientific community in how the flu virus lives, and history may hold the answers.

“After evaluating a number of published peer reviewed studies conducted over the last 70 years, we’ve learned that monitoring and maintaining proper humidity levels in your home to may reduce survival of the flu virus in the air and on surfaces,” said Jim McDevitt, co-author of the report, instructor at the Harvard School of Public Health, and a certified industrial hygienist by the American Board of Industrial Hygiene. “While the typical flu virus can survive on surfaces and in the air for up to 24 hours, the survival time in a more humid environment is markedly lower.”

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.”