At least 10 people were treated after inhaling mace in a Roxbury apartment building early yesterday. Boston firefighters responded just after 1 a.m. to a possible carbon monoxide incident at 10 Codman Park, according to Fire Department spokesman Steve MacDonald. They found several people coughing and complaining of difficulty breathing. A hazardous materials technician could not find any evidence of carbon monoxide. A man told Boston police officers a short time later that mace had been sprayed in his apartment, according to police spokesman James Kenneally. One woman was transported to Boston Medical Center; no arrests have been made, officials said.