Military shelters experience frequent periods of inactivity. During these periods, the shelters are sealed-up and often left in harsh environmental conditions. The SSD provides controlled breathing during diurnal temperature cycles to protect the shelter’s integrity. Additionally, air that passes into the shelter through the SSD during cooling periods will pass over the SSDs desiccant bed. This desiccant removes the moisture from the air before intrusion into the shelter and protects equipment from rust, mildew, and corrosion.