When the warmer needs de-scaling, the mode and starting temperature symbols will flash on the digital display. To ensure maximum effectiveness, you should de-scale your warmer every time it is required. To acknowledge the de-scale warning, press and hold the Power/Mode Selection or Volume Selection/Start Button for 3 seconds. If you do not wish to de-scale, please be aware that the unit will not remind you to de-scale on your next use, but will instead begin re-counting cycles until the next de-scaling is needed.