Le Comptoir Aroma's Gypsy Ultrasonic Diffuser has a 30ml water tank for use up to 4 hours.
Take it where you want with its USB power supply! It's also safe, with an automatic shutdown feature when the water level is low and protection in case of overheating.
Diffusion cover: 215 sq. Ft. / Water tank: 30ml.
Continuous mode: 2 hours / Intermittent mode: 4 hours