For many buildings that do not require space cooling, non-centralized equipment such as unit heaters provide space heating to building occupants. Unit heaters are a major source of energy use nationally, accounting for nearly 18% of primary space heating energy use for commercial buildings, and most prominently appear in warehouses, distribution centers, loading docks, etc. Several high-efficiency gas-fired space heating, or gas heater, technologies exist that consume significantly less energy than a conventional gas heater and can produce substantial energy savings if widely adopted. This report discusses a field demonstration to analyze the energy savings for one of these technologies, 100% outside air, high discharge temperature heating and ventilation (HTHV) direct-fired gas heaters, under normal use conditions at a warehouse outside of St. Louis, MO.