Discharge damper, two-position motor and interlock: motor-operated parallel blade damper that prevents warm air from escaping the building through the unit. The motor-damper end switch energizes the starter circuit when the damper is in the full-open position, and returns to a closed position during shutdown. Down discharge arrangement units available with our exclusive "Hassle Free Damper" internally mounted in unit.   Discharge louvers with air diffuser: discharges air in four directions with vertical and horizontal blades, and is field-installed. The blades can be manually adjusted to set direction of airflow.   Filter section: removable, hinged access door, with a 2-inch washable, aluminum-mesh filter, or a 2-inch pleated filter. Also available with 1-inch, 1.5 lb density insulation.   Fresh-air intake hood with birdscreen: prevents rain or snow from entering the unit with a 1-inch mesh screen on hood face; sized to fit unit's fresh-air intake. Shipped loose to be field installed.   Full-downturn inlet hood: prevents rain and snow from entering the unit by bringing air into the bottom of the hood with a 1-inch wire-mesh screen, and is field installed. Large hoods are shipped separately, and must be field assembled.   Inlet-hood filters, 2-inch: cleanable, aluminum-mesh filters mounted on the inlet-hood face in lieu of a separate filter section. Not available on TTH-M 227 and larger models.   Inlet screen: prevents material from entering unit. A 1-inch mesh screen fastens to unit's fresh-air intake.   Inlet damper, two-position motor and interlock: motor-operated parallel blade damper that prevents outside air from entering the building through the unit. The motor damper end switch energizes the starter circuit when the damper is in the full-open position, and returns to a closed position during shutdown.   Return-air filter, 80/20 units: 2-inch deep, aluminum mesh, or 2-inch deep, 30% efficient, pleated type; v-bank, filter section shipped loose for field mounting to the return-air connection.   Standard curb: 24-inch roof curb formed of 12-gauge steel; 14-inch curb is also available. Shipped separately, and must be field assembled. Insulation, cant, and wood nailer by others