Travel Carbon Monoxide Detectors Plug in: Plug and Play C0 Monitor for Home - Portable 4-in-1 Natural Gas and Carbon Monoxide Alarm with Temperature(°F) & Humidity for RV Hotel - 1 Pack is up for auction in Home & Kitchen. The current bid is $11.50, 48% below the $22.00 MSRP, in Good Condition. This auction has ended — similar items appear in live auctions regularly.