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What Is a Thermal Bag?

Helen Akers
Helen Akers

A thermal bag is an insulated container used to keep temperature sensitive products fresh. These types of bags are most commonly used to safely deliver food and medical vaccines. The insulation in a thermal bag ensures that both hot and cold temperatures are maintained while its contents are being transported.

In order to ensure safety, the temperature of many food items needs to be kept consistent. When sensitive or perishable food items are moved between locations, a thermal bag is a temporary source of temperature control. For example, pizza delivery bags use insulation in order to keep food warm so that it will not spoil by the time the customer receives it.

Man with a drill
Man with a drill

Pizza delivery is one of the industries that makes heavy use of thermal packaging. Since delivery drivers may have to locate addresses they are not familiar with, the thermal insulation in the bag makes sure the customers will not be dissatisfied with cold food. Thermal bags maintain the freshness of the food and give the impression that it was just taken out of the oven or microwave.

The interior of a thermal bag contains insulation, often in the form of padding made from a metallic material. For foods and other items that need to be kept warm, the metallic material helps transfer any escaped heat back to its originating source. Padding and metallic material also contains the heat within the thermal bag as long as it remains closed. The thermal insulation is a temporary solution to maintaining temperature control and should not be substituted for longer term solutions, such as a refrigerator.

Besides maintaining heat, thermal insulation can also keep items cold. Perishable and frozen food items, as well as vaccines, may need to be kept at certain temperatures while being transported. Ice packs can be placed in thermal bags to help supplement the insulation. An insulated shipping container is a good solution for smaller shipments of vaccines or food items that only need to travel short distances.

Another type of thermal bag is available for personal use. Some of the lunch bags or totes that are available for consumer purchase use thermal insulation. This can come in handy for individuals who want to bring their own lunches to work sites, but do not have access to a refrigerator. Delivery drivers who work outside of an office location and are constantly mobile typically find insulated lunch bags to be a great convenience.

Discussion Comments


@AnnBoleyn - You're right, using a cooler bag is a great way to be less wasteful, but perhaps that's exactly why not many grocery stores carry them. If the food spoils faster, then people would have to be back at the store to purchase more, right? Isn't that why many stores use plastic bags in the produce section instead of paper bags which help to minimize moisture and spoilage?


@lighth0se33 - That's actually a really great idea! It's just as environmentally-friendly as the regular cloth grocery bags but with the added value of keeping the food fresh. It's awful to come back from a shopping trip and find that all the fresh produce is already wilting. I'm sure if more grocery stores actually sold thermal food bags then more people would use them.


Thermal bags work great for carrying food to fellowship gatherings at my church. I had seen people using heavy crockpots to keep their food warm, but I didn’t want to make something that had to be carried in such a heavy container and plugged in when so many others were already using the outlets.

I started making casseroles and placing them in dishes with tight-fitting lids. Then, I placed the dishes in thermal bags. When everyone was ready to eat two hours later, the food was the perfect temperature. It was like it had been warmed in an oven on low.


My thermal lunch bag saved me from lots of stress with the shared refrigerator at work. I had been having problems with my food disappearing, so I decided to invest in a storage option to protect it.

One of the higher-ups at work has this obsessive need to clean out the refrigerator. She placed a sign on the door stating that it would be cleaned out every Friday, and anything without a note attached to it would be thrown away. The crazy thing is that she placed that sign up on a Tuesday, and that same day, she emptied out the fridge!

I was upset because a nice bottle of mine fell victim to her frenzy. So, I started keeping pouches of fruit juice and small water bottles in my thermal lunch bag, along with my sandwich, fruit, and veggies. The food stays cool enough not to spoil. The bag gives me the invaluable security of knowing my lunch is safe.


I use thermal pizza bags for picnics. When I go to the lake, I want to eat something more substantial than a sandwich to keep my energy level up and maintain my strength for swimming. I bought a couple of pizza bags that zip up nice and tight, and as long as I eat the pizza as soon as we arrive at the lake, it is still pretty warm.

After I take the pizza out of the oven, it immediately goes into the bag. I put it in my trunk for extra heat, so it can stay out of the range of the air conditioner. We live about an hour from the lake, so that’s why we eat the pizza as soon as we get there.


I love carrying thermal bags in my car when I go to the grocery store. I live nearly twenty minutes away, and in summertime heat, frozen items thaw out in transit.

I put my carton of chocolate frozen yogurt in a bag, and it keeps it from oozing out around the edges of the carton. I also place frozen fish and other meats in a bag. I am paranoid about my milk spoiling in the heat of the trunk, so it goes in one, too.

I first saw thermal bags for sale hanging on a hook at the end of the frozen foods aisle. I purchased several and used them that day.


I live in Arizona and I carry a thermal shopping bag to keep my cold and frozen items in. On hot days during the summer the walk through the parking lot followed by a drive in a sometimes boilingly hot car is enough to melt a carton of ice cream. And in Arizona you want to have your ice cream.

But once I switched to thermal grocery bags my problems went away. They are great for lots of other things to. I will take them to my sons soccer games to keep drinks cold. They are like mini coolers. I'm sure they would come in handy even if you didn't live in the middle of the desert.


I used to work in a pizza place and they were going to throw out a big flexible thermal bag that had a small rip in it. I said I would take it and then I brought it home and sewed and sealed the rip. Now I keep it in the back of my car at all times.

This is great because I hate to cook and I get a lot of takeout. My town is really spread out so a lot of times you will get food and have a long drive home. By the time you sit down to eat your burrito or Chinese or whatever is cold. But if I keep it in that thermal bag it stays incredibly hot no matter how long the drive is. It has saved my dinner eating experience. Not bad for a piece of trash.


I work as a medical courier and I carry a thermal bag over my shoulder every day at work. It is a large nylon bag that is stretched tightly over two insulated foam compartments. In one I keep samples meant to be kept cold and in the other I keep frozen samples. In a pocket on the front I keep room temperature samples. To keep things cool I use cold packs and dry ice that my company supplies me.

Here is what gets me though. This system is far from scientific. The refrigerated samples get really cold, the frozen samples get really warm, ambient samples go both ways depending on the weather. Despite all my best efforts it seems impossible to keep these samples at the right temperature. But it doesn't seem to matter. They always get to the lab and get tested just fine. That is something that I think about a lot while I'm driving around.

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