Look, if some gyro gearloose is worried about CO poisoning, a CO alarm loud enough to shatter a champagne glass is not expensive and you can mount one right alongside the heater. A simple finger clamp PULSE OXIMETER is DIRT CHEAP now and it will tell you to a ridiculously precise point EXACTLY how much O2 is in your blood and the reading takes 5 seconds. Even more paranoid? Some pulse oximeters have LOUD alarms, and the custom supreme models can be USB connected to a computer and tell you how many times you fart at night.