Starting of January 1st, carbon-monoxide detectors are required in (more or less) any dwelling in California. It is for your safety and for the safety of various devices’ manufacturers. They’re safe from going out of business now. Remember, the penalty for non-compliance is $200 (first offense).
But you still can save some real money if buying these devices on Amazon: today many of them, including those with high ratings, are offered at significant discounts.
Take a look and read the reviews. I also suggest looking at those with battery backup, and not those with only external power sources. It is known that when there’s a fire or emergency, power lines tend to become disconnected.
Your Little Advisor