Great idea! I’m normally put my battery operated CPAP inside my sleeping bag. This helps immensely and I believe prolongs the battery life also…I don’t have a CPAP. However, if it’s the thin plastic tubing that I’m thinking, I suspect you would need to add al layer of good insulation to prevent condensation. Does the unit heat the air when it adds humidity? If so, that might help with insulation. Otherwise, you might still get condensation eventually asthe tubing will eventually get to the air temperature no matter what you do.