Why are there medical tests before going to the high site?

ALMA's 66 antennas are located in the Array Operation Site (or AOS for short), a 40-minute drive from the observatory's camp. As AOS is 5,000 meters above sea level, anyone working there must be subjected to health tests to avoid risks.In this episode, Dania Lange, a nursery at the ALMA Observatory, explains how they test and monitor their staff permanently to be safe while performing their jobs and what symptoms could appear if their medical work is not done carefully.