Many thermometers, such as bimetallic stem thermometers, tend to lose accuracy over time, especially if they are bumped or dropped. If a thermometer is not functioning properly, there can be dangerous consequences. Employees should continually monitor the temperature of food, specifically for cooking, hot holding, and cold holding Time/ Temperature Control for Safety (TCS) Foods. This helps prevent pathogens from growing; however, if the thermometer is off by even a couple of degrees, the food could be in the Temperature Danger Zone (41°F to 135°F) and harmful pathogens could cause your customers to get sick. To keep this problem from happening, thermometers need to be calibrated often. There are a couple ways to calibrate your thermometer: (1) ice point method and (2) boiling point method. We’ll discuss how to calibrate your thermometer using the boiling point method.
The boiling point method is mainly used by food handlers who work with extremely hot food, such as in candy making. However, it is a useful technique to know no matter what type of food you are handling.
Follow these steps to complete the calibration:
- Bring a pot of water to a rolling boil. The pot can be any size; it just needs to be big enough to cover the tip of the thermometer.
- Insert the thermometer to cover the entire sensing area. This is usually indicated by a dimple or groove on the stem of the thermometer.
- Avoid touching the pot with the thermometer because it will give you an inaccurate reading. Hold the thermometer just below surface of the water.
- Wait for the thermometer to stabilize before adjusting anything.
- Find out what the boiling point of water is in your area and adjust your thermometer to that boiling point. This is the tricky part: boiling points are different at different elevations. For example, water boils at 212°F (100°C) at sea level. If you are in a city that is about 5,000 feet (1.5 km) above sea level, the boiling point should read 202°F (94°C). The higher you are above sea level, the lower the boiling point will be. Check the chart to learn the boiling point of water at your elevation.
| Boiling Point of Water | Elevation |
| 200°F | 6,000 ft |
| 202°F | 5,000 ft |
| 204°F | 4,000 ft |
| 206°F | 3,000 ft |
| 208°F | 2,000 ft |
| 210°F | 1,000 ft |
| 212°F | Sea Level |
And there you have it! Be sure to calibrate your thermometer often to ensure your food is safe. For more information about calibrating thermometers, be sure to watch our Food Safety Focus courses on Ice Point and Boiling Point Calibration. These courses can be found as Learning Extras in our Food Handler Training course, or they can be purchased individually or as a package by calling 801.494.1416.
—Janilyn Hutchings
