Most rooms can accommodate an air conditioner, but certain structural and spatial conditions must be met for proper and safe installation. Window-type units require an exterior-facing wall opening or window with sufficient support, while split-type units need an indoor wall with enough clearance for the unit and a nearby exterior wall or pathway for the refrigerant line and drainage pipe to reach the outdoor condenser. Rooms with no access to an exterior wall, extremely thick concrete walls that cannot be drilled, or insufficient electrical capacity may require additional preparation work or may be better served by a portable air conditioner that does not require permanent installation.