I took a nap in it. It's all good. You can't overpressure it if you want to (that's what the lower valve is for).

What would happen if the motor died? Would you still get fresh air? You are risking your life sleeping in this.

Part of why I used a blower rather than another type of pump is that you can still breathe in. You have to force the air through with your chest, which is tiring, but there's no danger. the idea is that you go out and get the blower replaced, at that point

You should add a second one-way value. Because with the open tube you are breathing back in the same air you are exhaling.

Try it: Turn off the motor, and take shallow breaths, see how much air you get.

It'll be way too hot to comfortably sleep in anyway.