Here on Chicago's North Shore the local codes requires Carbon Monoxide Detectors to be placed within 20 feet of all bedrooms in the home. But if you live in a single-family home with the hot-water heater, and furnace or boiler, in the basement, I think it's best to also place a Detector close to the bottom of the stairs as they exit the basement. It just makes sense because the gas-fired appliances that produce carbon monoxide – a gas which you can't taste, can't smell and can't see - is most likely released in the basement. Think of the Carbon Monoxide Detector in the basement as an early warning detection device to keep you and your family safe from harm.