Relative Humidity on the ISS and in the Classroom

Humidity on the International Space Station is usually kept between 40 and 60%, which is quite comfortable for Astronauts. Historic data shows that the mean and median are both near 46% RH. At present we suggest that you use 46% RH for all of your ISS sample data points. 

The ISS data streaming sites such as http://www.telemetry.space/ does not show the station's relative humidity in the band of data entitled Atmosphere. The Thermal Regulation data show that related to the AC system and not what the Astronaut's experience. We are developing an available data set that Living Space users could use to consult for relative humidity (available early 2019). 

Regarding Relative Humidity in the Classroom

The relative humidity plays a determining role in the quality of your indoor air. Health Canada recommends keeping the humidity above 30% in winter and making sure it doesn't exceed 55% in summer (ideally, it should be somewhere between those percent values at all times). When you consider that people generally are most comfortable when the relative humidity is approximately 40%, you can see how the RH of indoor air can take a toll on your biological and psychological well being. Low humidity causes static electricity, dry skin, lips and hair, scratchy throats and noses, and itching and chapping. If the RH is very low then you will feel cooler than the actual temperature due to your skin drying out too quickly.

High humidity can encourage bacteria to grow, dust mite, rot in wood, oxidation and rust on your indoor living space. Most people will find below 25% way too dry and it will affect people biologically. Above 60% RH and people react biologically and psychologically feeling it is way too wet, and it will cause people to feel hotter than the temperature actually is because sweat is not evaporating from their skin as easily or at all, which is the body's natural way of cooling and controlling temperature. If the RH is high you will feel warmer than the actual temperature. Understanding the biological and psychological effects of humidity can help both Astronauts and other earthlings in their attempts to provide optimal environmental conditions.

Please see the CurioCity Backgrounders on RH on

http://explorecuriocity.org/lsap/#/EducatorMindsOn2/2.5