It's made of durable plastic and the soothing vapors are activated by heat and released into the air when plugged into any wall outlet. This Vicks Vapopads plug-in also includes a convenient soft glow nightlight and adjustable vapor control that lasts up to 32 hours. It produces a non-medicated menthol scent that's bacteria-free and leaves no messy dust. It is ideal for keeping your respiratory system moist and relieving dry, itchy eyes. Use this humidifier with Vicks VapoPads in your bedroom as part of a good night's sleep during allergy season or when ill. Each package contains one vapor plug and four Vicks plug-in pads.