The inner pouch’s contact with air will trigger the reaction that causes them to heat up. To fully activate, simply remove the inner pouch from the outer package and shake vigorously for 15 seconds. Within a minute or so, they will be HOT! DO NOT OPEN THE INNER CLOTH POUCH!
Depending on ambient temperature product should take up to 1 hour to reach optimal range of 94-100 degrees and stay warm for up to 8 hours.