The World’s Coldest Ammonium Nitrate Free Instant Cold Pack! InstaKool delivers immediate cold therapy for first aid, providing comfort and reducing swelling after an injury. This disposable pack comes in three sizes and combines great price, quality and safety with an 18 month shelf life. Pack stays cold for approximately 15-25 minutes. InstaKool is latex free and haz-mat free, which makes it a great cold pack for any busy school nurse!