Fungal Concentrations in One Dust Sample, by Experimental Treatment
| Treatment | Sample ID | Fungal concentration (spores/mg dust) |
|---|---|---|
| Control | 4 | 21,700 |
| 85% RH | 4 | 1,160,000 |
| 100% RH | 4 | 619,000,000 |
The International Space Station (ISS) is meant to maintain 25%–75% relative humidity (RH) to assist humans. However, routine crew activities such as handwashing can create localized areas of elevated RH. These increases create conditions under which microbial growth can be a concern. Researchers collected dust samples from four ISS vacuum bags, creating these samples from each bag for twelve samples in total. Observed fungal concentrations (spores count per mg of dust) at each sample’s original condition—presumed to reflect the desired RH range—were used as controls for comparison with counts after exposure to 85% and 100% RH.