Five people are sent to the hospital following a carbon monoxide leak inside an apartment Wednesday morning in the Humboldt Park Neighborhood. Fire crews responded to the residence, in the 1600 block of North Keystone Avenue, where CO levels peaked over 350 ppm. The Chicago Fire Department said a man went to work with symptoms of CO poisoning. His boss took him back to the residence where other family members were found unresponsive. Three of the victims were transported to a local hospital in good condition and two others in serious condition. Several others have refused treatment. There is no word on the age and gender of the victims. Fire officials are reminding people to make sure they have a working CO detector in their homes.