Q. If one sensor reads higher than setpoint at 1.6 and two sensors read 1.2, what should you do? What do you suspect?
A. Begin with a diluent flush. If all sensors are now in agreement, don’t stop there. If it happens again, you may have a dual sensor failure. If you are using sensors that are old, they may not be able to achieve high values. The voting logic on your rebreather may reject two good sensors in this case. The best bet when you are suspicious of sensors is to bail to open circuit.
If you are in the back of the cave and don’t feel comfortable with an open circuit bailout, then you have other options. When your diluent is breathable at maximum depth, a diluent flush will solve any issue temporarily, giving you time to figure out what might be going on. Contrary to popular belief, dual sensor failures are very possible and more common than you might imagine. Think about it. If you install three sensors from the same manufacturing run, then treat them the same way and abuse them equally, then they have a common history. If you overuse sensors they could fail simultaneously. However, even if you don’t overuse them, a common history means the potential for simultaneous failure is much higher than otherwise.
