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Healthy Foundations

Relative Humidity

 

 

 

What is relative humidity?

Relative humidity is a ratio of the amount of water vapor currently in the air compared to the amount of water vapor the air could theoretically hold at that given temperature.

For example, 40 percent relative humidity, means that the air is holding 40 percent of the water vapor it could hold at that temperature.

 

Why does relative humidity matter?

Humans sweat to keep cool.

If the relative humidity for an 80-degree day is 100 percent, then your sweat will not evaporate into the air because the air is at its saturation limit. That’s not healthy.

If the relative humidity is too low, then the air will be dry and can result in the removal of moisture from your skin, nose, lips, mouth, etc. This can result in bloody noses, scratchy throats, dry mouth, and dry skin.

Humans are most comfortable between 40-60 percent relative humidity.

 

How does relative humidity provide virus protection?

Airborne viruses travel through infected aerosols of tiny water droplets. A person expels aerosols through talking, breathing, singing, laughing, sneezing, coughing, etc. These aerosols will change size depending on the amount of moisture in the air.

In dry air, aerosols shrink, making it easier for the virus to get into the body and infect the person. These smaller aerosols weigh less and are picked up in airstreams allowing them to travel farther and longer making increasing their rate of infection. These smaller aerosols are dangerous in areas where the air is recirculated.

In moist air, aerosols are larger, heavier, and fall to the ground quicker than their counterparts. Once they fall to the ground, they are still able to infect people, but if you wash your hands frequently and avoid touching your face then you severely decrease your chance of infection. Unfortunately, air with high relative humidity such as this is uncomfortable and inhabitable for humans.

By keeping it between 30-60 percent, you’re providing enough moisture to keep your body’s immune response high and enlarging the virus enough to lower its infection rate.

 

How do I know that my house has the proper humidity?

If your skin is dry, you have a scratchy throat, and you are getting bloody noses, then the air is likely too dry. Dry air can also crack your wooden furnishings.

In moist air, you’re likely also very miserable. You probably have mold or mildew growth, feel clammy, and may even have a pest infestation. One of the best indicators that the air is too moist, is if the air has a mildew smell.

 

Healthy Air Solutions

Aprilaire HumidifierAprilaire DehumidifierAprilaire Healthy Air System

 

Resources:

EPA - https://www.epa.gov/mold/mold-course-chapter-2

CDC - https://www.cdc.gov/niosh/topics/indoorenv/temperature.html

ASHRAE - https://www.ashrae.org/file%20library/technical%20resources/covid-19/i-p_s16_ch22humidifiers.pdf

 

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