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Common Questions about Infrared Thermometers

The outbreak of COVID-19 has placed the infrared thermometer in the limelight, as a preferred tool for fever detection. The non contact infrared thermometer allows temperature to be taken without skin contact. This makes it a hygienic method to take the temperature of different people. However, the use of infrared sensor in the infrared thermometer has caused some to worry about its safety and potential side effects. Read on to find out the answers to some common questions about the non contact infrared thermometer.

Are all non contact infrared thermometers suitable for human body temperature?

There are three types of non contact infrared thermometers, namely non-medical grade infrared thermometer, general purpose infrared thermometer, and human body infrared thermometer. Their specifications make them suitable for temperature monitoring in different contexts.

  • General purpose infrared thermometers are typically used to measure over a wide temperature range. The accuracy of general purpose infrared thermometers is commonly more than +/- 1degC or 1% (whichever is higher). While it is possible to measure human body temperature with the general purpose infrared thermometer, it is important to note that the reading obtained is only an estimate of the human body temperature. For an accurate measurement, which is especially important for fever detection, it would not be recommended to use the general purpose infrared thermometer due to its low accuracy. Instead, use a human body infrared thermometer with rated accuracy of at least +/- 0.3degC, or ideally +/- 0.2degC.

  • Industrial temperature guns/Non-medical grade infrared thermometers will be equipped with one or more laser sources to indicate to the user which area they are measuring, as well as the approximate spot size for those with more than 1 laser source. You should definitely avoid looking at the laser source itself to avoid damage to the eye (with long term exposure). These thermometers are non-medical grade and thus would not be recommended for human body temperature measurement and fever detection.

  • Human body infrared thermometers have a narrower temperature measurement range of around 34 to 43degC, and accuracy of at least +/- 0.3degC. It is calibrated, and thus suitable, to measure human body temperature. The human body infrared thermometers are also medical grade infrared thermometers. These typically do not have any active source. The detectors are passive in nature and are used to pick up the infrared radiation from your forehead and convert the thermal energy to an electrical potential.

For the remainder of the article, the term “infrared thermometer” will only refer to human body infrared thermometers that are medical grade.

Does an infrared thermometer release infrared rays? While the device is called an infrared thermometer, it does not emit infrared radiation or infrared light (rays) like your infrared LEDs on your remote control. In fact, they work in the opposite way - infrared thermometers detect the infrared emission radiated from our bodies. The infrared thermometer captures the infrared radiation from our body (the measuring point) and converts that into a temperature reading.

(All objects emit infrared radiation when they are above absolute zero temperature (0 K). This includes the human body. Read “A Brief Introduction to Infrared” for more information.)

How safe is the infrared thermometer for human body temperature measurement?

With proper use*, the infrared thermometer is perfectly safe for frequent usage - even if you were to do it on an hourly basis everyday. There are no side effects to worry about when using a medical grade non-contact infrared thermometer. This is because the non-contact infrared thermometer does not emit any infrared radiation (as mentioned above). Thus, there is no need to be concerned about having your temperature taken by a medical grade infrared thermometer every time you enter a building, shopping mall or store etc during this pandemic.

The infrared thermometer is also safe to use for kids. However, do note that some non-contact infrared thermometers come with simple LED light to indicate where you are pointing the sensor at on the other person. While typically harmless, you should still avoid pointing the light source to your kids’ eyes just to err on the side of caution.

*Proper use refers to using the infrared thermometer for the intended purpose, such as measuring the body temperature from the forehead.

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