How do we know?
↻ One of the pages with a moving picture
A doctor patented an ice-making machine in 1851.
- Tiny bacteria live on many foods. At room temperature, some can double every 20 minutes!
- Cold slows them down. A fridge should stay at 40°F or below.
- A freezer at 0°F stops bacteria from growing, but it doesn’t kill most of them.
- Cold air must flow around the food, so don’t pack the fridge too full.
Dr. John Gorrie cooled his patients’ rooms with ice. On 6 May 1851, he got patent No. 8080 for an ice-making machine.
Today the rules come from food-safety experts: a fridge should stay at 40°F or below, and a freezer at 0°F.
Food that needs the fridge shouldn’t sit out longer than 2 hours. On a day above 90°F, the limit is 1 hour.
Wow number
2 hours Food that needs the fridge shouldn’t sit out longer than this. On a day above 90°F, the limit is 1 hour.
Myth or fact?
Freezing food kills all the germs on it. Myth. Freezing stops most bacteria from growing, but doesn’t kill them.
Putting hot leftovers in the fridge breaks it. Myth. The FDA says it doesn’t harm the fridge.
Think about it
Why do you think leftovers cool faster in small containers than in one big pot?
Where in the world?
Apalachicola, Florida, USA where Doctor John Gorrie built a machine to make ice — 29.7258° N, 84.983° W.
Where these facts come from
Every number on page 89, and who measured it
This page tells us how cold a fridge and freezer should be.
Refrigerator Thermometers — The U.S. Food and Drug Administration (FDA)
fda.gov/food/buy-store-serve-safe-food/refrigerator-thermometers-cold-facts-about-food-safety
We checked it on 31 October 2026
This page tells us that freezing doesn't kill most germs.
Are You Storing Food Safely? — The U.S. Food and Drug Administration (FDA)
fda.gov/consumers/consumer-updates/are-you-storing-food-safely
We checked it on 31 October 2026
This page tells us about Dr. John Gorrie and his 1851 ice machine.
National Statuary Hall Collection — The U.S. Capitol Visitor Center, where Gorrie's statue stands
visitthecapitol.gov/apps/nshc/statue/gorrie
We checked it on 31 October 2026
Has this changed?
How a fridge keeps food safe is not going to change.
The safe-food rules come from food-safety experts and can be updated, so it is worth checking them from time to time.
Words from this page
- bacteria
- Tiny living things, too small to see, found almost everywhere.
- patent
- An official paper that says an invention belongs to its inventor.
Try it!
Check how cold your fridge is.
1. Ask an adult for a fridge thermometer. 2. Put it in the middle of the fridge and close the door. 3. Check it the next morning. Is it at 40°F or below?
What happens: you find out if your fridge is cold enough to slow germs.
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