PURPOSE: To maintain the working environment for an operator preferable by providing a CO removing device in an operation chamber itself for various working vehicles which work in the environment in which CO exists in high density, thereby effectively removing the CO.

CONSTITUTION: A CO removing device body 3 arranged adjacent to an operation chamber 2 of a ceiling moving crane installed in the environment in which air including detrimental substance such as high density CO, NOX, SOX exists. A circulation port 7 communicating with the chamber 2 is provided at the position faced with a suction port 5 provided with a prefilter 6 at the lower portion of the body 3, and a prefilter 8 and an air flow rate controller 9 are mounted at the port 7. A filter 10 for removing the detrimental gas except CO, a high performance filter 11 for removing fine powder dust and a CO removing filter 12 are arranged sequentially from the bottom in the body 3, and purified air is blown by a fan 13 through a diffuser 14 into the chamber 2.