The Genesis collector canister was cleaned and assembled in two Class 10 vertical flow cleanrooms. (A Class 10 cleanroom allows no airborne particulates greater than 0.5 µm and a maximum of 353 particles of this size per 10 cubic feet of air.) One of the Class 10 rooms is a "wet" lab used for cleaning spacecraft parts with ultrapure water (UPW). UPW, which has ionic concentrations in the low parts per trillion level, is a very aggressive solvent. A small plant furnishes 10 gallons per minute of pure water with a resistivity exceeding 18 MΩ.

The second Class 10 room is used for assembling the payload - NASA's cleanest assembly room. Since people are the dirtiest part of a cleanroom operation, scientists assembling the payload are completely enclosed in Gore-Tex suits equipped with a filter that removes particles > 0.3 µm from exhaled breath. A Class 1000 corridor is adjacent to the Class 10 rooms and allows viewing of the cleaning and assembly process. Other rooms in the facility are for personnel gowning, sample storage, and removing outer wrappings from in-bound objects.