Extech Instruments Psychrometer with Nist

WHISPER-QUIET: Ultrasonic air diffusion produces less than 36 dB for a quiet humidification that you even cannot hear it is on
TWO-STAGE FILTRATION: Ceramic and Activated Carbon filters purify water before it is diffused; breathe better, safer air with a two-stage filtration humidifier
LARGE 4-LITER CAPACITY: Allows for 20 to 30 hours of continuous use; covers up to 200 sq.ft (10~20m²) in your bedroom, living room, or office