Most, if not all masks, use silicone in all parts that touch the body. Silicone does not contain bishenol-A (BPA).
It is likely that the rigid plastic shells of masks and rigid plastic humidifier tanks contain BPA.
However, the FDA maintains that current BPA exposure from plastic bottles is safe for humans. In this case they are referring to bottles containing various beverages, including water, for human consumption.
CPAP equipment is a wonderful source of improved health. Let's not be afraid of BPA.