Apparatus for heating, namely filters and filter frames for ducts carrying warm air, outlet grills and frames for air ducts, air ducts and supports therefor, driers using warmed gases, air heaters; apparatus for refrigerating, namely filters and filter frames for filtering cooled fluids; apparatus for ventilating, namely air purifiers, filters and filter frames for ducts carrying air, outlet grills and frames for air ducts, air ducts and supports therefore, air conditioning ducts and fans for...