Portable humidifiers may reduce airborne influenza virus: Study

A new scientific study published in the open access, peer-reviewed journal Environmental Health indicates that the use of portable humidifiers in the home may reduce the survival of airborne influenza virus by controlling humidity indoors.  Specifically, when homes are kept at the optimal 40-60 percent relative humidity level -- a term used to describe the amount of water vapor in the air -- flu virus survival in the air can be dramatically decreased by up to 30 percent for homes with radiant heat and 17 percent for homes with forced air heat.

The study is the first to look at airborne influenza survival in the home, using computer modeling software developed by the National Institute of Standards and Technology, and is part of a growing body of research indicating that in more humid environments, airborne flu virus survival time is markedly decreased.  The study also suggests that forced air heat, which provides more rapid mixing of indoor air throughout a residence, may require increased humidification to achieve optimum relative humidity levels.

"The findings of this study are important for households, schools, and offices this winter, when relative humidity levels can be as low as 10 percent," said Dr. Jim McDevitt, Ph.D., co-author of the study, instructor at the Harvard School of Public Health, and a certified industrial hygienist by the American Board of Industrial Hygiene. "A portable humidifier is an adequate tool to elevate relative humidity levels if there is concern that levels are too low, as is typical during winter.  To determine humidity levels in the home, consumers can use a device called a hygrometer."

"Eliminating a considerable share of airborne influenza viruses through the use of a humidifier could be very beneficial to households this winter," 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.  "However, families should be careful not to go overboard with over-humidifying, because the optimal relative humidity range for indoor comfort and decreased influenza is between 40 and 60 percent."

The study, titled "Modeling the airborne survival of influenza virus in a residential setting: the impacts of home humidification," is published in the September 3 issue of Environmental Health.  To read the full-text journal article and about methodology, visit www.ehjournal.net.

The study, sponsored by Kaz, manufacturer of Vicks brand humidifiers, comes from an independent team of scientists and researchers.