Posted by UniHeat, Your Shipping Warmer Experts on 16th Sep 2025
The Science Behind Heat Packs: How They Generate Warmth
The Science Behind Heat Packs: How They Generate Warmth
Have you ever wondered how UniHeat packs stay warm for hours—or even days—without batteries or electricity? These small, lightweight packs rely on simple chemistry and careful design to produce safe, consistent heat. Understanding how they work can help small businesses, hobbyists, and shippers use them more effectively.
What’s inside a UniHeat pack?
Heat packs contain a precise blend of natural, non-toxic ingredients, typically including:
- Iron powder – the core ingredient that reacts with oxygen.
- Salt – speeds up the reaction process.
- Activated carbon – distributes heat evenly.
- Vermiculite – helps retain and regulate warmth.
- Water – necessary for the chemical reaction to occur.
The role of oxygen
When you open the packaging and expose the pack to air, oxygen triggers the iron to oxidize—a process similar to rusting, but much faster and controlled. This reaction releases heat as a byproduct. The salt and water help speed up and sustain the process, while activated carbon and vermiculite ensure the heat spreads evenly and lasts for the intended duration.
Why the heat lasts so long
UniHeat packs are carefully engineered with just the right mixture of ingredients. The porous packaging allows oxygen to enter at a controlled rate, which regulates how quickly the iron reacts. This balance makes it possible for some packs to provide warmth for 40 hours, while others are designed to last up to 96 hours.
Safe and reliable warmth
Because the reaction is natural and self-sustaining, UniHeat packs do not overheat or require external power. That’s why they are trusted for shipping tropical fish, reptiles, small pets, plants, and temperature-sensitive goods around the world.
Recommended UniHeat warmers
Different situations call for different durations. Here are some options to consider:
Frequently Asked Questions
1) Are UniHeat packs safe to use with animals and plants?
Yes. They are non-toxic and designed for live animal, plant, and perishable shipping. Just avoid direct contact—always use a barrier.
2) Why do I need to shake or expose the pack to air?
The packs are air-activated. Oxygen triggers the iron to oxidize and release heat. A quick shake helps spread ingredients evenly to start the process.
3) How long do heat packs last?
UniHeat offers different durations. The 40-hour pack suits overnight shipping, while the 72 and 96-hour packs handle longer or colder routes.
4) Can heat packs overheat?
No. They’re engineered to release a steady, safe level of warmth, unlike electric heaters or chemical packs that may spike in temperature.
5) Are the ingredients eco-friendly?
Yes. Iron powder, salt, carbon, and vermiculite are natural and safe. After use, packs can be disposed of with regular household waste.