You can, but the temperature may rise by 3–5°F after several hours. If you dislike the heat, run it during the day only, or use a small oscillating fan to circulate the air.
Position the unit on a level surface with at least 20 cm (approx. 8 inches) of clearance on all sides and 30 cm (approx. 12 inches) above the air outlet for proper ventilation.