These 40 hour shipping warmers are best for two day shipments. Remain patient as these heat packs can take 30 to 45 minutes to start generating noticeable heat. Uniheat shipping warmers are the first designed especially for small pets, tropical plants and other temperature sensitive products. This duration of heat pack is a best seller among hobbyists and businesses whom need to control the shipping temperatures!
For best results it's important to open your shipping warmers well ahead of your intended pack out time. This will give you amply time to make sure they activate properly. During this time it's important to make sure your heat packs are properly staged as well. We've found it's best to allow them to heat up in the shipping container you'll be using them in. This will prevent your heat pack from coming into contact with any solid, cold surface which may cause your heat pack to stall out from heating up properly.
Once you've noticed that the heat pack is warming it's important to wrap them individually in newsprint. Newsprint fosters the ideal environment for your heat packs to continue to rise towards their peak temperature. Remember all heat packs need to breath in order to generate heat. Newsprint provides a breathable barrier that will insure your heat pack ventilation holes do not become blocked once placed in the shipping containment.
Finally be aware that shipping methods and requirements are going to vary in each shippers personal scenario. In order to repeatably make successful shipments it is strongly recommended that each shipper performs trials test to establish safe procedure that is tailored to your own personal situation.