Question Of The Week: Wintertime Indoor Air Quality?

women using a tissue to wipe her nose.As the cold winter months approach in many regions, many building occupants (and the facility management teams in their buildings) are unaware that their dry indoor environments and low indoor air humidity levels are promoting the spread of pathogens including flu and cold viruses.

As facility management teams in office buildings and other facility types put their indoor heating systems into high gear to combat the cold temperatures outdoors, the factor of air humidity levels is often overlooked. However, indoor air humidity levels can have a dramatic effect on the movement and lifespan of bacteria and cold and flu viruses. Making matters worse, dry indoor environments cause the mucous membranes in the nose and the lower respiratory system to dry out, impeding the body’s natural immune response against airborne bacteria and viruses.

Nortec, a manufacturer of commercial and industrial humidification systems, recently shared insights on this scenario. “The optimal relative air humidity levels for indoor spaces should be 40% to 60%. If the relative humidity drops below 40%, you are creating the ideal environment for the spread of harmful viruses,” said Duncan Curd, GM of Nortec. “Unfortunately, many public and private spaces such as office buildings, schools, hospitals, and homes have a relative humidity as low as 20% over the winter months, due to dryness caused by traditional commercial and residential heating systems.”

Nortec has noted that aerosols expelled by infected individuals through coughing and sneezing, and even breathing and speaking, are loaded with viruses or bacteria embedded in water mucous, saliva and dissolved salts. As they leave the airways, the aerosol droplets (with a moisture saturation of almost 100%) lose almost 90% of their weight due to water loss if exposed to much drier room air, resulting in these high, infectious salt concentrations circulating through the air.

In crystalline form, the infections materials can spend hours floating and recirculating through dry air (with relative humidity below 40%) and can travel significant distances depending on the air current. However, if the relative air humidity in the space is within the optimum range of 40% to 60%, the salt concentration decreases to a level where most of the viruses cannot survive and become deactivated. The risk of infection within this optimum range for relative humidity is minimal.

“The overall result of insufficient humidity levels in so many public and private spaces over the winter months is high levels of illness and productivity losses in the billions, to both businesses and society as a whole,” said Nortec’s Curd. “This is an epidemic affecting businesses and public spaces. Respiratory illness and disorders are among the top three reasons for work absenteeism due to illness, and researchers also suggest that 15% to 30% of infections within hospitals are transmitted by air. These problems are largely preventable with better indoor air conditions, through the implementation of residential and commercial steam humidifiers.”

Meanwhile, commercial air purifiers are another tool facility management can utilize to clean air and improve the indoor air quality in buildings. This is done by removing airborne bacteria and viruses that remain suspended in dry air for prolonged periods of time.


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