By creating a comfortable humidity level, the Philips AVENT ultrasonic humidifier will help protect your baby against sore throats and irritation to the mucous membrane. This has a positive effect on building up resistance to infection.A hygrometer and thermometer handset is included to let you monitor and maintain the ideal humidity and temperature levels of your baby’s room. (Ideally, between 16 to 20ºC with a relative humidity of 40 to 60%.)