From Bulbapedia, the community-driven Pokémon encyclopedia.
Outside of the Purify Chamber.
The Purify Chamber (Japanese: リライブホール Relive Hall) is a machine located in the Pokémon HQ Lab, developed by Michael's father and Professor Krane to make purification of Shadow Pokémon faster just in case Cipher would ever return to Orre after the events of Pokémon Colosseum. The Purify Chamber can be accessed via PC or at the HQ Lab; the main difference is that the HQ Lab includes a holographic display of the Pokémon stored in the chamber, and the final purification step can only be performed directly at the HQ Lab.
The Purify Chamber works by slowly opening a Pokémon's heart with time. Each of its nine Sets operates via the type of Pokémon placed in it and whether it is super effective, normal, or not very effective against neighboring Pokémon in the same set; the more effective the type matchup between two Pokémon is (e.g. Dark on Psychic), the greater the flow inside the set and the faster the Pokémon's purification will proceed. For the purposes of the Purify chamber, Normal is treated as strong against itself, making it possible to achieve maximum flow even with exclusively single-typed Normal Pokémon.
The above method works the same for all Shadow Pokémon except Shadow Lugia, who is believed to be immune to purification. To purify Shadow Lugia, it must be placed into the chamber when all nine Sets are at the maximum tempo (termed a "perfect circle"). Shadow Lugia can then be instantly purified.
Inside of the Purify Chamber
A sample setup of a Set that has strong flow all around would be as follows: