Healthy Habits: Humidity in Schools and Influenza

Before break, we had a bunch of kids out at my school. The flu and other illnesses ran rampant through many Minnesota schools. While it is good practice to teach children proper hand washing, to use sanitizer, and cough into your sleeve, there is one important health piece that schools can do to help protect students and their teachers. Did you know that if a room is at the right humidity, which is 30 to 60%, that respiratory viruses and others aren't easily spread? It's true. However, if the humidity level of the school is too low, then the virus can run rampant. A local Minnesota company, DriSteem, has been helping schools and other buildings across America stop this at its core.

• How does humidity affect disease transmission?

A key study done in 1985 showed that the optimal conditions to minimize risks to human health in indoor environments occur between 40-60% relative humidity, or RH, at normal room temperatures. Maintaining RH within this 40-60% range decreases the number of viruses, bacteria, and allergens found in the environment while also preventing skin dryness and eye irritation. This study is still referenced by HVAC professionals today and forms the basis of standards for healthy built environments set by the American Society of Heating, Refrigeration, and Air Conditioning Engineers (ASHRAE).

The Mayo Clinic in Rochester, MN, tested this concept in a preschool classroom. Researchers wanted to determine whether increasing the relative humidity of classrooms to 40-60% would reduce the capacity of influenza, commonly known as the flu, to survive on classroom surfaces or in the air as aerosols. Commercial-sized humidifiers were installed in two classrooms, to compare against two control rooms that had no humidification. This study showed that the humidified rooms had:

• A significant decrease in % total air samples containing influenza A
• A trend toward decreased % of surface samples containing influenza A
• A significant reduction in influenza A presence for total air and surface samples
• Fewer infectious samples
• Fewer flu-like illnesses reported

• Why is it so hard for schools and other large buildings to maintain proper humidity levels?Humidification systems need to be accurately sized for buildings and their total load.  It’s also important to adapt the humidification system as environmental demands, as well as building configuration and use change over time. Working with a knowledgeable local representative is essential to selecting the right solution. 
• How can schools find the right solution to regulate humidity?
  To identify issues caused by fluctuating or low relative humidity levels, facility managers should analyze the conditions and complaints, and monitor relative humidity (RH) levels and temperature. An inexpensive hygrometer, an instrument for measuring the humidity of the air, can be used to track indoor humidity levels. Again, working with a knowledgeable local representative is the best way to select the right humidification system.