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Keeping Food Safe with an IR Thermometer

Infrared Thermometers can Improve Accuracy and Efficiency in Food Safety Quality Control Processes

The CDC reports over 3,000 deaths and over 47 million cases of foodborne illness every year in the United States. While these numbers may seem staggering, there has actually been a great deal of improvement in food safety controls in recent years, including the 2011 passage of the Food Safety Modernization Act. The first time it has been updated since 1932!

New systems and solutions are being introduced throughout the food industry as new technologies improve monitoring and processes for refrigeration, food handling, transportation and all aspects of the food production and delivery chain. These new systems help prevent and reduce the risk of pathogens and exposures.

One such new technology are digital infrared thermometers. These non-contact thermometers can offer unique advantages for measuring and monitoring temperatures in food safety applications for food plants, distributors and retailers.

Advanced features such as laser pointers, high and low temperature alarm settings, scan and hold functions and data-logging of maximum and minimum readings provide specific advantages for food safety professionals.

Eliminating Direct Contact Reduces Risk of Cross Contamination

Contamination occurs most often by direct contact with previously

Food safety
Contamination of clean food usually happens through contact with contaminated ones

contaminated food, equipment, utensils, and surfaces, or by handling of foods by people who have come in contact with contaminated foods, utensils or equipment. Because this is true, a non-contact process of temperature measurement can mean a serious reduction in contamination risk. If you never touch it, and the thermometer never touches it, you (and the thermometer) are eliminated as potential sources of contamination. When this approach is applied across a supply chain, it results in a significant reduction in cross contamination risk.


By delivering accurate non-contact monitoring of surface temperatures, infrared thermometers can provide critical data without the contamination risks associated with contact thermometer measurements. Hand held IR thermometers can greatly increase the efficiency and effectiveness of food safety regulators and quality control procedures throughout the food industry, provided their limitations are well understood and they are used correctly.

IR Thermometer Accuracy and Limitations in Food Safety Temperature Monitoring

Most IR thermometers operate effectively in the most critical temperature range for food safety regulation and quality control monitoring. Typically, the required range is from 0°F-525°F (-18°C to 275°C). Many of today’s IR thermometers operate to a higher upper range of  500°C or more, although food industry applications won’t require these higher temperatures.

More critical, and often the source of confusion, is the accuracy specification. The accuracy, or measurement tolerance range tells you how far from a precise temperature reading the unit can deviate and still be considered accurate within specifications. The measurement accuracy of most IR thermometers is ±3.5°F (±2°C) at temperatures between 32°F (0°C) and 212°F (100°C), and typically increases above and below this range.

There are a couple of things to understand about an IR thermometer and its accuracy range which will improve the reliability of your results and make you a more intelligent user of an IR thermometer.

Digital Infrared Thermometers are Optical Instruments

The first is this: Digital IR thermometers are optical instruments. While some do have laser guides which can make it very easy to see precisely what you are taking a measurement of, the instrument is not using those lasers to take the measurement. The thermometer is taking a reading of infrared light emitted from the surface being measured and converts that sensed radiation into a temperature reading using an algorithm.

This information can improve how you use an IR thermometer.

First, you’re not measuring heat in the same way a contact thermometer does. You’re taking an optical measurement of infrared light. This also means the optical sensor can be impacted by the reflectiveness of the surface being measured, which is why some surfaces will require a different emissivity setting to get an accurate reading. You can learn more about emissivity, what it is and how it works, in this article.

The second thing to understand about the way digital IR thermometers measure temperature is that, in general, readings do not tend to ‘drift’ or ‘float’ as they usually do in contact thermometers.

The optical sensor is quite reliable, and should deliver accurate readings without drift over time, so long as the instrument is not mishandled or abused.

Things that can affect the accuracy of the reading include direct contact with steam. Readings generally return to normal once the unit has had time to dry completely. Likewise, smoke, or dirt in the air, exposure to gas fumes and other volatile fumes can all affect the operation of the sensor.

Other factors that could potentially impact accuracy include extreme cold or hot temperatures. For that reason, always bring the unit to room temperature before using it. The digital IR thermometer is an electronic instrument, so of course it can be damaged by severe rough handling, submersion in water, etc.

If you’d like to determine precisely where your individual IR thermometer reading falls within its accuracy tolerance range (see above), there a couple of ways to do it. You can compare several test readings with a known accurate contact thermometer to determine the offset. Or you can set up a simple ice bath (see this video from NIST on how to set up a test ice bath correctly) to determine the offset at 0°C (32°F).

Once you’ve performed either of these tests, you will know exactly what your individual IR thermometer reads at the chosen comparison temperature or the ice point temperature of 0°C (32°F).

Non-Contact Means Surface Temperature Readings Only

Because digital IR thermometers are measuring light radiation in the infrared spectrum, they are always measuring the surface of the objects being measured. A surface will act as the measuring surface regardless of its opacity.

In short, this means you cannot take measurements through glass or any transparent material. Even if your laser guides are shining red dots on an object on the other side of the glass, the measurement will be of the glass surface between the instrument and the visible laser dots.

For example, if you try to take a measurement of a display case from outside the glass, the instrument will give you a surface temperature reading of the glass, not the case contents. The appearance of laser guides on the display contents does not mean the glass is not interfering with the measurement of those contents.

Accurate measurement requires a direct line of sight between the sensor in the IR thermometer and the object being measured. No glass, transparent plastic or other barrier can be between the sensor and the object to be measured. You cannot take accurate measurements through any type of glass, not oven windows, display cases or freezer case doors.

Surface temperature readings mean surface temperature only. This means that for solid objects, such as a roasting chicken, the reading is only telling you the external temperature of the food, NOT the internal temperature of the food, which you need to know to determine if the food is cooked or not.

This does not mean, however, that you cannot measure the temperature of liquids or soft foods like whipped potatoes. It does mean that to do so requires that you manipulate the liquid or soft foods by stirring, in a slow and even motion, up from the center of the container while scanning the surface to get true temperature readings of the entire mass. By doing this you will see that the temperature can vary considerably from top to bottom of an unstirred mass of liquid or semi-solid food.

Soup Measurement
Soup Temperature can be Measured by using a spoon to mix the soup or get the bottom part of the soup into the top and measuring the soup

This is the only way to get accurate readings for liquids or soft foods with a digital IR thermometer. Simply scanning the surface of a pot of soup, for example, will not give you the temperature of the interior liquid.

This can be particularly important when measuring temperatures during food production processes where liquids need to achieve certain temperatures before the next step in the process can be taken, as in, yogurt making, yeast breads, or making cheeses.

Using pre-set high and low temperature alarms for monitoring target temperatures can further aid in preventing foods from becoming too hot or too cold.

Advantages of IR Thermometer in Food Safety Applications

Advantages of IR thermometers for food producers, distributors and retailers include:

  • Safe measuring of foods too hot to touch
  • Efficient measuring of fast moving foods on conveyor belts
  • Easy measuring of foods in difficult to reach locations
  • Accurate readings of different foods during rapid successive measurements
  • Accurate readings of foods subject to changing temperature influences

IR thermometers make monitoring of critical equipment simple and fast:

  • Cooling systems

    Food safety requires constant montoring of freezers, food storage refrigeration units and hot food service appliances.
    A Non-Contact Infrared Thermometer can help Store Managers Track Temperatures to Ensure Food Safety.
  • Walk-in dairy and cold food rooms
  • Storage areas
  • Refrigerated truck interiors
  • Refrigerated display cases
  • Hot food stations
  • Salad Bar and cold food stations

Quality Control and Regulatory Applications

Digital IR thermometers are well suited to both quality control work and regulatory inspection work.

No Cross Contamination Risk

Non-contact measuring offers the advantage that no decontamination is required between jobs or applications. (Although wiping the unit down with a clean cloth between applications may be recommended depending on the application environment.)


Non-contact measuring offers the advantage that no decontamination is required between jobs or applications. (Although wiping the unit down with a clean cloth between applications may be recommended depending on the application environment.)

No Temperature Draw Down

Non-contact also means no temperature changes introduced by the measurement activity itself. This eliminates the problem of  direct contact measurements which can cause a temperature draw-down in the foods being measured.

Precise Targeting of Items Being Measured

Non-contact measuring in combination with laser guides easily and clearly identifies the surface being measured. This makes scanning foods simple and fast in storage, freezers, refrigerated cases, trucks, on conveyor belts, or in other dynamic areas of production without disrupting operations, or having to manually move or handle the food.

Establish Baselines and Improve Efficiency and Quality

IR thermometers can be used throughout food production and quality control processes to establish baselines, improve efficiency and monitor operations over time to ensure conformity and compliance throughout a production process or even across an entire supply chain.

By routinely scanning and testing process lines and procedures the IR thermometer can identify and improve target temperature ranges, efficiency and product quality.

Identifying anomalies or discrepancies in a scanning process means that scans can be repeated if necessary and further determinations can be made by interrupting an operation to do smaller statistically significant sampling to either confirm or disprove any findings of the scanning when needed.

While additional testing steps are not eliminated by IR thermometers, the need for such testing can be identified by initial scanning and monitoring with the IR thermometer, making early detection and correction more likely and more consistent.

Further Risk Reduction

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