He was born in Manhattan on March 28, 1882.
Hirons was of French extraction; he immigrated to Massachusetts as a child. Hirons worked as a draftsman in the Boston architectural office of Herbert Hale from 1898 until 1901, before entering the Massachusetts Institute of Technology; on graduating in 1904 he received a Rotch Travelling Scholarship to study at the École des Beaux-Arts in Paris. MIT's Paris prize enabled him to continue his European studies until 1909.
On his return he established an architectural practice in New York with Ethan Allen Dennison (1881–1954). Hirons and Dennison produced many commercial structures in the Beaux-Arts and Art Deco styles: Delaware Title & Insurance Company, Wilmington, Delaware; Federal Trust Company Building, Newark; City National Bank, Bridgeport, Connecticut; Home Savings Bank, Albany, New York; State Bank & Trust Company, West 43rd Street and 8th Avenue, New York; Beaux-Arts Institute of Design, 304 East 44th Street; Suffolk Title and Guarantee Company Building, 90-04 161st Street, Queens, New York. Their Childs Restaurant, Coney Island, New York (1923), employs colorfully glazed terracotta tiles in a fanciful resort style combining elements of the Spanish Colonial revival with numerous maritime allusions that refer to its seaside location". The Davidson County Courthouse of 1936 by Hirons and Dennison (with involvement of Nashville local architect Emmons H. Woolwine) is listed on the National Register of Historic Places.
He designed many public buildings, including the Worcester Memorial Auditorium and the Clark Memorial at Vincennes, Indiana.
He was president of the Beaux-Arts Institute of Design (1937–39), of which he had been a founder. He taught architecture at Yale University and Columbia University. His portrait by Henry R. Rittenberg is in the collection of the National Academy of Design.