Rooftop filter curbs are designed to offer filtration for a packaged unit. The units ship fully assembled and feature all-welded construction, factory insulated walls, integral filter rack, and access door for servicing filters. Both custom and standard designs are available and ship within a standard production cycle. The unit is built specifically for health care, green building, K-12 education, airport, government, and manufacturing facilities. Standard features include a single-access door; 1-, 2-, or 4-inch slide-in racks; and 1-inch racks can be used with 6- or 12-inch cartridge, bag, or carbon filters. Additional options include built-in roof pitch, special heights, and pressure-treated wood nailer.