Safety is our number one concern, both for you and for us. So, we have multiple monitoring devices spread throughout the house. There are smoke detectors spread throughout the bedroom areas on levels one, two, three and four, and carbon monoxide / natural gas detectors on levels one, two and three. The only problem with these are, there's a lot of them, and occasionally, from time to time, a battery gets weak, and causes the alarm to slowly beep.
There are over fifteen different natural gas / carbon monoxide / smoke detectors located throughout the house. We change the batteries at least twice a year.
If one of these devices starts to annoy you, they're easy to fix.
The CO detectors generally look like this:
Of course, when an alarm goes off, get out of the house and call for help. Carbon monoxide poisoning is dangerous and insidious; you can't smell it, and at that altitude (the house is at 9700 feet), hypoxia is a real danger. Smoke can asphyxiate, and natural gas, well, it's explosive. Let the pro's figure out what's leaking or burning. We don't expect any issues with this, as our natural gas heaters are brand new, but, one always has to be prepared for any sort of emergency.