The warmer is activated by pressing the orange . This triggers the internal solution to warm the unit in just *0 seconds. The cold feed is gently warmed as it flows through the specially designed channels on the outside of the warmer. By the time the feed reaches the teat, it is at natural breast milk temperature (****4 degree C). Once the has been pressed, the warmer has been carefully designed to stay warm for up to an hour. The warmer will need to be recharged after every feed following one of the three charging methods (microwave, boiling or electric steam steriliser). All yoomi parts are **0% BPA-free, meet the highest safety standards and have undergone extensive testing by an array of experts.