Infrared Thermometers: Your Top FAQs Answered

Infrared Thermometers: Your Top FAQs Answered

At the height of the Covid-19 pandemic, you couldn’t enter a shop or public place in Toronto (or anywhere) without yielding to a person holding a gun-shaped device that they had to point at your forehead. Mercifully, this device is designed to help save lives, not put them at risk.

We are talking about infrared thermometers now commonly used to screen for high fever. 

What makes these thermometers special? Besides fever screening, what are the other uses of these no-contact thermometers? Are they even accurate?

So many questions, and not enough space to answer them all in one article. We will answer the most frequently asked:

What is an Infrared Thermometer?

An infrared thermometer is a device that uses the thermal energy (aka heat) a subject emits to measure its temperature from a distance. On human beings, IR thermometers measure skin temperature, which is then algorithmically computed to produce a core body temperature measurement.

Also known as no-contact thermometers, IR guns, as they are also known, allow accurate temperature measurement in situations where contact to the subject is unsafe or where it is not possible because of a physical barrier.

The device has become one of the most common tools in the fight against Covid-19. It is used to detect fever and screen for Covid infection at public areas. 

By allowing remote temperature measurements, IR thermometers help the person operating the device to keep a safe distance from the subject in case they are infected with the Covid virus. A high temperature indicates a fever and possible infection with the acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus.

Other Common Uses of Infrared Thermometers

While infrared thermometers have found widespread usage during the Covid-19 pandemic, they have other clinical as well as industrial applications. 

Improve Safety and Prevent Damage to Equipment

In the industry, infrared thermometers are used to monitor for heat loss or gain, which is important for preventing engine malfunction, equipment breakdown, and insulation failure.

At home, a handheld infrared thermometer can be useful when doing general car maintenance and repair. It can help you check for overheating so you can isolate areas where the engine trouble may be emanating.

Ensure Food Safety in Kitchens and Restaurants

You can use a no-contact infrared thermometer to measure the temperature of soups and other foods that have to be cooked at high temperatures and served while hot to kill and head off bacteria.

With an infrared thermometer, you won’t have to dip the thermometer‘s probe in the food and risk contaminating it. It makes it safe and easy to check if the food isn’t undercooked or if it hasn’t sat for too long.

Similarly, there are foods – like fish – that must be stored at very cold temperatures to preserve freshness and keep bacteria away. An infrared thermometer can be used to check if the fish has been stored at the ideal temperature, which tells you whether it is still safe to consume.

Handheld Infrared Thermometers

The handheld infrared thermometer is shaped like a small pistol, with a sensor positioned at the end of the barrel. It has a back-facing screen where you would have the rear sight on a pistol that displays the temperature reading. 

The thermometer has a grip that houses the battery compartment and which you use to focus the device on the subject. Like a pistol, it also has a trigger that you press when you are ready to take the temperature measurement.

Handsfree, Non-contact Infrared Thermometers

While handheld IR thermometers are convenient for mobile applications, where you don’t have to move around with the thermometer a hands free infrared thermometer works best. They are now commonly seen on entrances to retail outlets and public buildings, either used alone or with automatic hand sanitizers.

With a hands-free IR thermometer, you simply screw it to a wall so people can self-measure their temperature. The thermometer remains in place where it’s installed and automatically measures temperature whenever it senses radiation coming from a human subject.

With all this said, it is important to mention that there are some IR thermometers that while they work well for industrial applications and general home use aren’t approved for clinical use. Industrial IR thermometers, for one, are not suitable for measuring human body temperature.

How do Infrared Thermometers Work?

Infrared thermometers use an infrared laser scanner to measure the temperature of a stationary or moving subject. When used correctly, the devices produce accurate temperature measurements.

When focused on a subject, an IR thermometer uses its sensor to detect the thermal energy (infrared light) the subject is emitting and converts it through an electronic process into a temperature reading. 

Are Infrared Thermometers Accurate?

Infrared thermometers are accurate as long as you are using a model that is designed for the exact purpose. That’s because one IR thermometer may be designed and calibrated for an application that’s different from another’s. 

An industrial IR thermometer, for example, cannot accurately measure core body temperature of a human being. The accuracy of infrared thermometers depend on these and other factors:


Depending on application, the thermometer has to be calibrated with the subject’s emissivity in mind. How well an IR thermometer can detect thermal energy and accurately measure temperature depends on well the subject being measured emits heat. 

Different surfaces have varying levels of emissivity. If the thermometer is not calibrated to detect and measure temperature from a specific surface, the reading it gives may be inaccurate. Bare metal, for example, is not as emissive as human skin.

Wave Length

Infrared thermometers are also affected by humidity. At least as far as the wavelength the particular model is designed to operate at is concerned. 

IR thermometers work optimally at wavelengths for which they are calibrated because different wavelengths have different levels of sensitivity to humidity. Humidity levels determine how much thermal energy is required for the thermometer’s sensor to detect it.


When operating the IR thermometer, geometry is also important. Specifically, the distance between the thermometer is a factor in the accuracy of the temperature reading. The farther away the subject is, the larger the thermometer’s field of focus.

A greater distance from the subject expands the testing area, increasing the risk that the thermometer will also detect temperatures of surrounding objects. 

To get an accurate temperature reading, you have to know what the distance-to-spot ratio is for the thermometer you are using. This ratio gives you the thermometer’s measuring distance. 

Using Infrared Thermometers to Monitor Body Temperature

An infrared thermometer is a useful device to have around the home, place of business, or workplace. Because they can be used without physical contact with the subject, they are perfect for fever screening during outbreaks of highly transmissible viral diseases, as with the current Covid-19 pandemic.

If you are going to be using an IR thermometer to measure body temperature for the purpose of screening for possible infection with Covid or any other high fever-causing virus, it’s a good idea to know which parts of the body to measure:

What Parts of the Body Can You Take Temperature With an Infrared Thermometer?

The best parts of the body to take a temperature using an infrared thermometer are the forehead and wrist. The forehead is an accessible part of the body that’s not usually covered. 

For the most accurate reading, aim for the temporal artery that runs down the center of the forehead. Bring the thermometer as close to the forehead as possible.

However, wrist temperature measurements are now considered to be more reliable. Sweat, makeup, and headgear can all affect the accuracy of forehead measurements. The wrist is mostly exposed and isn’t normally covered in makeup and does not sweat as much as the forehead.

Like the forehead, the wrist has veins running directly beneath the skin. Generally, blood vessels show the most accurate measures of body temperature. Just make sure you are not wearing a watch on that wrist when you check your temperature.

Are Infrared Thermometers Dangerous?

Contrary to misinformation on social media, infrared thermometers are not dangerous. The common line is that these devices project infrared light (read, radiation) towards the body, posing health risks. This is false.

An IR thermometer measures the amount of infrared light or thermal energy the body is emitting. It does not project the said infrared light rays onto the body and therefore poses no health or safety risks.

Where to Get Your Infrared Thermometers in Toronto

As we have learned, infrared temperatures have many applications. You can use them to monitor body temperature and for a variety of tasks at home, including in the kitchen. So there will still be plenty of uses for your handheld IR thermometer long after the current Covid pandemic.

As well as gloves and other PPE, you can get your infrared thermometers from the AGMD Group. We supply both handheld and hands-free infrared thermometers, supplying all of Toronto and the surrounding areas. Contact us here for your orders.

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