PLEASE SEE PICTURE BEFORE BUYING THIS UNIT. The First Alert CO600 Plug-In Carbon Monoxide Alarm utilizes an electrochemical carbon monoxide sensor. This carbon monoxide detector plugs into any standard electrical outlet and features an end-of-life warning alerting you when to replace the detector. When carbon monoxide levels become elevated, a loud 85-decibel alarm alerts you to the threat. Loud 85-decibel alarm sounds when CO levels are elevated CO detector alerts you to elevated carbon monoxide levels in the home Single test/silence button for efficient testing of CO detector Simple plug-in design, plugs into any standard electrical outlet 20% RESTOCKING FEES AND SHIPPING WILL BE CHARGED. IF ITEM IS FUNTIONAL OR INCOMPLETE. An Important Message Regarding USPS Tracking Numbers Due to high volume of shipments sent through USPS, Tracking numbers get recycled on occasion. This means, when you receive the notificaiton that your package has been shipped via USPS, and you try to track the status of the package, it may show your package was Delivered even though the label was just generated. Please don't panic, the solution to this issue is to wait until the Post Office scans the label, then the tracking information will update accordingly. Please let us know if you have any questions. Your feedback is extremely important to us! If you are satisfied with our service please take the time to give us positive feedback. We tremendously appreciate it! We strive for your complete satisfaction. Likewise, if you have any issues, please contact us first, and we promise we will do our best to satisfy your needs and solve the problem. If we resolve your problem, we kindly ask you to still leave us positive feedback. Your kindness will be extremely appreciated!