User Guide


Getting Started

  • You don’t have to take the packs out to charge them. Put the whole vest with packs included into the freezer or fridge for 45 to 60 minutes (or ice water for 20 minutes) until they are fully solid again.
  • If you took the packs out of the vest, slide the frozen cooling packs into each of the pockets in the back of your UnderCool.
  • Your UnderCool is now charged and ready to be worn.

How to Wear

  • Unfasten the Velcro.
  • Place your arms through each arm hole.
  • Fasten the Velcro on your front, tight enough so the cooling packs rest firmly on your back.
  • Wear whatever you like over your UnderCool.

Cooling and Recharging

  • Undercool will cool as long as the packs haven't phased to complete liquid - this may occur in 1-2 hours depending on your level of activity and the ambient temperature.
  • To recharge the packs, put them back in the freezer or fridge for 45 to 60 minutes (or ice water for 20) until they are fully solid again.
  • Enjoy a day safe from the heat!

Washing and Care of UnderCool garment

  • Remove all cooling packs from the vest. (They will be destroyed if you keep them in there!)
  • Close the velcro front and place in a small net laundry bag.
  • Wash UnderCool in cold water with like colors.
  • Dry and store flat.

Care and Storage of CoolingPacks

  • To get the most out of your packs, keep them frozen when not in use.  This can be done by leaving them in the freezer, fridge, or anywhere colder than 70F/21C
  • Our cooling packs will last for 2-3 years depending on usage.
  • Cooling packs left in their melted state for extended periods of time will reduce the lifespan of the cooling packs.
  • To wash your cooling packs, use warm soapy water in the sink.  Do NOT put them in your washer, dryer, or dishwasher.
  • For discounts on replacement packs, check out our Recycling Program.


Consult your health care professional prior to using this or any body cooling product for a medical condition. UnderCool cooling packs are designed for the specific objective of cooling the body. ThermApparel will not be liable for injuries or damages resulting from misuse or misapplication of our products.