Mobile Quarantine Facility

During the build up to the manned lunar landing, there was growing concern that the astronauts might bring back some sort of "moon germs" and infect the Earth; no Earthlings would have immunity to this foreign plague, the thinking went, and there would be mass extinctions as the lunar microorganisms ran rampant. Refer to Section V of the Biomedical Results of Apollo or Chapter 7 of Where No Man Has Gone Before: A History of Apollo Lunar Exploration Missions for additional (and less dramatic :-) accounts of the proposed precautions.

In addition to the eventually implemented "biological isolation garment", or BIG (plural, BIGs), a specially-converted Airstream trailer was configured to prevent the release of any of those pesky lunar organisms.

NASA photos 69-H-1196, S69-21881, and S69-40147 show the astronauts and the MQF.