Feb 032014

Not only is Fargo cold for six months of the year but once inside the air is dry. I can feel my skin dry up and start to itch. We make sure our humidifiers are working. They’re almost as important as our furnace. But my shins aren’t the only reason to humidify the air. Machines work better, wood doesn’t shrink or crack, and optimal humidity will even keep the doctor away. Gary L. Berlin in the February issue of Engineered Systems, writes on the topic in his article, “Restoring The Low Limit For Indoor Relative Humidity.”

Berlin describes the research history into humidity and health. He covers the what the industry has done to through its ASHRAE established standards to keep humidity at recommended level. And how more work needs to be done to keep indoor relative humidity from falling too low.

See this Sterling Humidity Chart. A decrease in bar width indicates decrease in effect.
Source: ASHRAE, adapted from Sterling et al., 1985.  Lennox.com

Sterling Chart (Optimum relative humidity range to minimize harmful contaminants)

In the early 1980s, Elia Sterling of the University of Vancouver did an extensive study of previously published research concerning indoor relative humidity and its effect on the occupants of an indoor space. This study established that both high and low relative humidity levels had a deleterious and costly effect on the health and productivity of the occupants of a facility as related to bacteria, viruses, fungi, dust mites, respiratory infections, allergies, asthma, and ozone in the workplace, schools, and home.

Relationship Between Humidity and Influenza
A Viability in Droplets and Implications for Influenza’s Seasonality

The recommendations include “maintaining indoor relative humidity above 40% will significantly reduce the infectivity of aerosolized virus.” (IAV)
In October 2012, the NIH released its extensive study. Results and conclusions  were as follows: “At higher Relative Humidity (RH), larger droplets would settle more quickly due to gravitation because they do not shrink as much. Once settled on a surface, they serve as a reservoir for contact transmission. Low RH not only helps preserve the viability of IAV but also enables IAV carrier aerosols to persist longer in the air because of their smaller size and lower settling velocity that results in more vigorous evaporation.”
Additional consideration must be given to the seasonal costs of the common cold, pneumonia, and other non-viral respiratory tract infections. When considering average staff salary and benefits at $35,000 to $45,000 annually, or about $180 per day, what is the cumulative cost of one day of absenteeism, productivity losses, healthcare, and temp services when required? What are the costs to provide humidification for the people in your workplace and your client’s workplace to help protect them from acquiring the seasonal cold, flu, pneumonia and other VRTI’s? Keep in mind that they might be a recipient as well as a transmitter to others. Source

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