Alexander Hall

For a room that size, aim for an ultrasonic unit with a tank around 600 to that model ml and adjustable mist. On low or medium it will run through the night without refilling, and the larger reservoir keeps the output steadier so scent reaches the corners. Look for a timer with at least 2, 4, 8 hour presets and auto shutoff. Placement matters too and put it a couple of feet off the floor and as central as you can without blocking airflow. Quiet enough for sleep when the fan is smooth and there are no button beeps. Works great.