No political subdivision or private volunteer fire department whose fire fighting forces are rendering outside aid pursuant to this subchapter shall be liable on account of any act or omission on the part of such forces while so engaged, or on account of the maintenance or use of any equipment or supplies in connection therewith nor shall any commissioner, chief, or the superior officer of a fire department, fire company, or other firefighting force acting pursuant to this subchapter be liable on account of any act or omission on the part of any of his subordinates while such subordinates are rendering aid pursuant to this subchapter under the command of an officer other than himself.