Computations of air bubble collapse dynamics usually neglect thermal conduction, but recent computations show about a 3-fold reduction in bubble gas temperature if thermal conduction is included. However, an isothermal collapse at ambient temperature is even more likely because the air molecules collide with and stick to the bubble walls during bubble expansion and are not available for compression heating during collapse. The probability of isothermal collapse is shown to depend on the mean free path of the air molecules moving through the H₂O vapor molecules within the bubble during bubble expansion and is sensitive to the lowering of ambient temperature to the freezing point.