The following words as used in sections 7-303 to 7-306, inclusive, shall have the following meanings: “Municipality” includes each town, consolidated town and city, consolidated town and borough, school district, fire, sewer and other district, improvement association or any other political subdivision of the state upon which is placed, or which has assumed, the duty of extinguishing fires and protecting its inhabitants from loss by fire. “Work” or “duty” includes the time spent and duties performed while at fires, answering alarms, returning from fires, attending fire drills or classes, conducting tests or trials of any of the apparatus or equipment normally used by a fire department, instructing or being instructed in fire duties, and any other duty which is ordered to be performed by a superior or commanding officer in the fire department.