In 1869, Benjamin Sturtevant patented the first hot blast apparatus, marking the beginning of the modern air-blast apparatus as applied to heating, ventilating and drying applications. The early "Sturtevant System" was centralized with air forced by a fan across steam coils then conveyed through ducts to all parts of the building. The line would expand to include unit ventilators for schools and suspended/floor type heaters for commercial/industrial work.
It was nearly a full decade after Nesbitt Co. introduced the first unit ventilator in 1917 that Sturtevant started a product line, though they patented a unit ventilator as early as 1915. As long-time believers in the Central Air System, they viewed the initial units as too bulky and noisy to be seen as a viable alternative.
With the creation of a light-weight copper heating surface,(developed by Aerofin Corp. which Sturtevant co-founded) in the 1920s, these issues disappeared and Sturtevant jumped into the fray. Originally developed for schools, unit ventilators would be in great demand in public and private buildings.