To alleviate security and maintenance problems, primary mechanical and electrical equipment should be separated from inmate areas. In determining whether to use a local or central plant in large facilities, a central plant offers better maintenance and efficiency benefits. Another decision is whether to use direct radiation or an all-air system for heating and cooling. With small windows, an all-air system is preferable because it provides the medium for heating, ventilating, and smoke control. Because it is almost impossible to provide secure access to balancing dampers, air distribution systems should be self-balancing. In deciding whether or not to provide a cooling system, a rule of thumb is that it need not be installed in geographic areas with fewer than 700 cooling-degree days. Criteria for smoke evacuation must be determined early in facility design. Among the critical factors to consider in evaluating an effective smoke control program are negative versus positive pressurization of cells, automatic versus manual controls, egress restrictions, inmate control measures, and community liability. The proper selection of control schemes depends on local codes and fire marshal requirements. Further study is needed to establish workable criteria that best meet facility needs.