seven ephors":ns4wp6b3 said:
How many heat pack depends not on the size of the shipment for most situation, but rather, on how good of insulator is used to box the content. If you use an open bird cage, you will need a lot more heat pack than a stylofoam box.
Having shipped thousands of boxes in the MO industry, I can say your kinda wrong here. True and open box would need more, but that's a moot point as no one ever ships in an open box, and it's against the TSA rules to do so
I never used more then two in an Indo Size box, 1 per FLA half box, 1 per level of a PI box, 2 per Tongan box, 2 per Bali box, 2 per Marshall box, and 2 for a SI box.
You can definitly over do a box with heat packs. To many (like 2-3 in a small box) will lead them to use up all the o2 to fast, and you'll only get half the heat time. Stick with 1 - 2, and if doing a small Igloo, use 1x 20+ hour one. Activate them prior to putting them in (make sure they're warm first), use a loose packing of newspaper, and follow the typical red guideline as to what side is up. IF they get wet, they will cease to produce heat, so be sure to keep some dry newspaper between them and the bags. HTH