Aeris CompuMask Operating Manual page 68

WARNING: If your CompuMask stops working for any rea-
son while operating as a Dive Computer, it is important that
you have anticipated this possibility and are prepared for it.
This is an important reason for not pushing the no decom-
pression and oxygen exposure limits, and a critical reason to
avoid entering decompression. If you dive in situations
where your trip would be ruined or your safety would be
jeopardized by losing the use of your CompuMask, a backup
instrument system is highly recommended.