The Apollo 11 crew in the van returning from a Countdown Demonstration Test (69-H-1057). Armstrong, Aldrin, and Collins (left to right) with suit tech Joe Schmidt. Although the astronauts have removed their helmets, they are still using their Portable Oxygen Ventilators to provide air circulation and cooling. The units attached to the suits have white hoses while the unit on the left has black hoses. Perhaps because each unit could only provide oxygen for a limited amount of time, at least two sets of units were used sequentially from the time that the crew started breathing pure oxygen in the suiting room until they were hooked up to spacecraft oxygen.
Source: Apollo 11 Image Library.
Source: ApolloArchive, AP11-VAN-NOID.