The New! Medik-Mini® HEPA filter attachment. Our smaller and more affordable option. HEPA (high efficiency particulate air) filters are the highest efficiency filter available for filtration of small particles. The first HEPA filters were developed in the 1940's by the Atomic Energy Commission to full-fill atop-secret need for an efficient, effective way to filter radioactive contaminants. They were needed as part of the Manhattan Project, which was the development of the atomic bomb. HEPA filter technology was declassified after World War 2 and allowed for commercial use. HEPA filters have been traditionally used in hospital operating and isolation rooms, pharmaceutical and computer chip manufacturing.