Instruct: Classify a review into positive or negative sentiment.
Query: BEWARE First Alert CO400 - Does Not Work

I bought this CO detector, installed batters, and the test button successfully sounded the alarm. Held the unit in a burning fireplace, silence. Held it under burning paper, silence. Held it for one minute, one inch from the tailpipe of my running car, silence. Consider the Kidde CO detector instead.UPDATE: Now I read that CO detectors cannot be tested, as I tried to do above. You just buy them, and hope they work, and if they do not, you ... die? How does the Consumer Product Safety Commission EARN their money?