Air coolers operate by drawing warm air through a damp cooling pad, which uses water from an internal tank to stay moist. Adding ice packs or ice cubes can enhance the cooling effect. These devices are most effective in hot, dry climates where moisture evaporates easily. On the other hand, portable air conditioners use a refrigeration system to remove heat from the room. They expel hot air through an exhaust hose, making them effective even in humid conditions. Air conditioners are rated by British Thermal Units (BTU), with higher BTU models suited for larger spaces.