After a building has been optimized, proper operations and maintenance (O&M) becomes the tool that will enable it to sustain its best performance. As might be expected, as building systems become more efficient and more tightly controlled, they also become more complex. In turn, so does O&M. Therefore, this column assumes that everyone understands the importance of general maintenance of equipment to maximize its lifespan, optimize efficiency, and minimize operating costs. In green buildings, however, it often is necessary to go beyond the proverbial "boxes."