Everyone knows not to use hand warmers for a heat pack in their shipments.
They'll cook your gecko real quick. It's the sad truth.
Why would they do such a thing though?
What's inside these little packets that they heat up like the the sun and 72hr heat packs do not?
Certainly some magical ingredients are the difference, or perhaps some advanced chemical composition....
If you lean towards the mystical, you'd be surprised to know that all heat packs, from hand warms to 96hr monster packs, have the same ingredients.
The only thing that differs-
Think if you wanted to boil some water.
The ingredients are always the same-
The recipe always the same-
Water + Hot
Now if you wanted to boil a cup of water, would it boil faster than a gallon?
This is the exact same thing that's happening with heat packs.
The Big Reveal
Heat Pack Magic Powder-
cellulose(like Wal-Mart Parmesan), iron powder, activated carbon, water, vermiculitw to hold the water, and salt.
The ingredients are all the same, the only thing that differs is size.
The chemical reaction takes place a lot faster, generating higher heat in smaller packs over a shorter duration.
This is why a hand warmer heats up super hot but lasts only a few hours.
This neat chart from Ship Your Reptiles shows the difference in peak heat for each heat pack size that we typically see in reptile shipping.
As you can see, the smaller packs hit a higher peak heat, with the most common pack, the 40hr, being especially uncomfortably high.
For these reasons we only ever recommend a 72 hr heat pack for Crested Gecko shipments.
Their size allows them to maintain a lower surface peak temp of 115* and stay that temperature throughout the shipment.
Given heat packs are required for shipments sub 40° in conjunction with a solid state Cryopak (72°), its ideal to use the best one for the species your working with.
I know some people's response is "Well I used 40hr Uniheat Packs and all was good!"+
but that's not an answer originated from a person that puts that extra thought in their shipping.
Don't @ me.