A layer of hot rock. The upper most part of the mantle and the crust together form a rigid layer. Like a road tar softened by the heat of the sun, this part of the mantel is somewhat soft - it can bend like plastic. Is a layer of molten metal that surrounds the inner core. Is a dense ball of solid metal.
In many countries, including Canada, having smoke and carbon monoxide detectors in the house is the law. The reason is simple: these alarms save lives. Many house fires occur at night. If there is no smoke detector, those sleeping in the house may not notice the fire and will be overwhelmed by smoke.
The response time and response-level of a carbon monoxide detector used as a building safety alarm varies by model. But in general, at 400 ppm of CO a Carbon monoxide detector will respond in minutes and at 30 ppm or below the CO detector is designed not to respond for 30 days.