Corrected entry: Although the premise of the episode is the complete failure of Serenity's major systems (life support, navigation, etc.), the gravity stays on throughout the episode. "Stays on," because a ship would require a major, operational electromagnetic system to mimic gravity - or it would need to be in a controlled spin - either of which option would fail as the rest of the ship did. As well as freezing and asphyxiating, by the rules of the episode, Mal and the others should be floating throughout.
Corrected entry: During the commentary for Shindig, one of the costume designers comments on the leather bands Zoe wears around her neck, saying that they are a symbol of her marriage to Wash, which is why she 'never takes them off'. However, in the flashback scene showing the first meeting between Zoe and Wash, she is wearing the bands.