Bests & Worsts Reviews from Amazon

I bought this unit in the spring of 2017 and installed it in my basement near the furnace. A few days ago (just under two years later), the heat exchanger in the furnace cracked and it started leaking carbon monoxide into the basement and distributing it throughout the house. Two CO/smoke combination detectors that I had on my second floor went off, but this unit remained completely silent. The fire department measured 160 ppm of carbon monoxide in the basement where this unit was located, far higher than what they measured on the second floor. After this incident, the test button on this unit confirmed that the batteries were still good, so I have no idea what the problem was. I'll be replacing this unit with something that hopefully works.