Infrared Thermometer Basics

How to Use an Infrared Thermometer

An infrared thermometer, sometimes called a laser thermometer, is an invaluable tool in a commercial kitchen, allowing you to quickly and accurately determine surface temperatures from a distance. This can be handy for checking griddle surface temperatures or verifying when an open deck oven is ready to bake. Infrared temperature guns are also a great choice for frozen foods, which can be impossible to penetrate with probes. Because there is no contact with the food products, it's not necessary to clean and sanitize the thermometer between uses, though the handle should be cleaned if used by a cook who just handled potential cross-contamination sources. The ease of use makes this type of thermometer ideal for most food safety checks. In order to get an accurate reading, it is important to use an infrared thermometer properly.

How Do Infrared Thermometers Work?

To understand why infrared thermometers need to be used differently than others, it's important to understand how they work. Infrared energy is a type of thermal radiation the thermometer can read from a distance. However, the thermometer's ability to do so can be limited based on the emissivity of the object.

Emissivity is how well the surface of an object radiates infrared energy. Organic materials, such as meat and plant byproducts, are rated at 0.95 emissivity, while shiny surfaces usually have much lower ratings since they reflect so much of the energy directed at them. To address that issue, you can apply a thin layer of oil, an organic material, to any metal surface you need to measure by infrared thermometer before you bring it up to temperature. However, some models will allow you to adjust the emissivity rating to get a more accurate reading from non-organic materials.

When Should I Use Infrared?

While an infrared thermometer can be incredibly useful, it is not always the right tool for checking temperatures in the kitchen. The most important thing to know is that an infrared thermometer only measures surface temperatures, so it should not be used for taking internal food temperatures. However, models are available with foldable probes that address this shortcoming. Because this type of thermometer uses a laser reflecting off the surface to determine the temperature, air that carries dust particles, smoke, and moisture can interfere with the temperature measurement.

Infrared thermometers also cannot measure the temperatures of items behind glass or other transparent surfaces, even if you can see the red circle on the item. If you try to measure temperature through glass, you will only get a reading of the temperature of the glass itself. Similarly, the thermometer can only read the temperature on the surface of water.

Using an Infrared Thermometer

The most important thing to know about using this type of thermometer is its best uses. It is ideal for checking the surface temperatures of griddles, pans, and deck ovens. It can check the surface temperatures of refrigerated or frozen items, but only for items that are fully chilled; it cannot determine that the center of the products have chilled to safe temperatures. It can provide a quick and easy way to check the temperatures of items displayed on buffets, but only after the products have been mixed to ensure temperatures are fairly uniform throughout the pans. It should not be used for solid items like steak or chicken, as the internal temperatures of such foods can vary greatly from the surface temperatures.

Infrared thermometers usually have trigger-like buttons, but some models have thumb-activated buttons. These buttons activate the thermometers' light projection, which displays a circle on whatever the thermometer is aimed at. The area highlighted in the circle determines where the temperature is read from, and that area increases as the thermometer is pulled farther away from the surface. Check the manufacturer's literature to see how far away your thermometer should be held when measuring temperatures, but be aware that moving too far away may affect the accuracy of the reading.

While basic operation of an infrared thermometer is simply point-and-click, you can also use the information about emissivity above in some cases. For reading the temperature of a non-organic surface like a pizza oven deck, you may want to invest in an infrared temperature gun that allows you to adjust the emissivity reading. Follow the manufacturer's guidelines on making those adjustments to ensure you get the most accurate readings possible. If you will need to measure both liquids and solid foods like proteins, consider selecting an infrared thermometer with a probe.

Here are some additional tips to help you get the most out of your infrared thermometer.

  • Do not look directly into the beam – the laser can cause permanent eye damage.
  • Stir all liquid and soft foods before measuring temperatures.
  • Sudden ambient temperature changes can make it difficult for the thermometer to get an accurate reading. If you need to record temperatures in a walk-in cooler, place the thermometer in the cooler 20 minutes before you start taking measurements to ensure more-accurate results.
  • Remove all covers, such as glass doors and plastic film, before taking the temperature of a product. There should be no barriers between the thermometer and the product.
  • Regularly clean the thermometer, especially the lens, to ensure accurate readings.
  • When checking the temperature of a griddle or pan, add oil to the surface and allow it to come to temperature before taking a reading.