First of all, you need to determine if it is alarming to CO or to LP. My Safe-T-Alert is 8 years old, Model 70-742. Anyway, when the CO alarm goes off, it does four beeps, then five seconds off then four more beeps and has a steady red light. If LP is detected, the audible signal is constant and the red light flashes.
Four nights ago at 3 am, my CO detector started sounding. I thought it was malfunctioning as I had no source of CO in my trailer going at the time. However, I had also installed a battery operated CO detector in the bedroom about a year ago and it was showing 30 ppm also. I thought maybe someone outside was idling a vehicle or running a generator or something similar, but no such thing.
I opened a couple of windows and turned on my exhaust fan. Both detectors cleared and went to zero within a few minutes. Everything was fine until that evening, when both detectors went into alarm again.
Long story short, I went online and researched what if anything could cause a false reading on CO detectors. Hydrogen off of a battery was one. I had just added water to my house battery the day before. So, I checked the battery. When I opened the battery compartment, I found a strong odor and a very hot battery with less than 9 volts. Evidently, hydrogen off of that battery had made it's way into the trailer and caused the CO detectors to alert. Replaced the battery and no problems for two days now.