Temporal artery thermometers and non-contact thermometers are both used to measure body temperature, however they work in different ways.

A temporal artery thermometer uses infrared technology to measure the temperature of the temporal artery, which is located on the forehead. In comparison, non-contact thermometers use infrared technology to measure the temperature of the surface of the skin, typically used by scanning the forehead. 

While both methods are non-invasive options to measure body temperature, non-contact thermometers are considered more inaccurate because they measure the temperature on the skin surface rather than utilizing temperature of the body's core with the temporal artery method. 

Why are Non Contact Thermometers Highly Inaccurate? 

Here is why no-touch thermometers are not accurate for detecting fevers:

Reason #1 It Measures Skin Surface

One reason for non-contact thermometer inaccuracy is that they measure the temperature of the skin surface rather than the body's core temperature. As a result, the thermometer may not accurately reflect the individual's true temperature if they have a fever.

Reason #2: The Scan Distance and Positioning

Positioning and scan distance are another reason that causes inaccuracies for non-contact thermometers. To get the most accurate reading, no-touch thermometers must be positioned at the correct distance from the skin surface. However, the misuse of this thermometer of an incorrect distance from the skin can often cause inaccurate readings.

Reason #3: Environment Temperature

Another reason affecting non-contact thermometer accuracy is the environment temperature where the measurement is taken. The environment temperature can also impact the accuracy of the non-contact thermometer, which is sensitive to ambient temperature. This sensitivity means that if the temperature in the room is different from the person being measured, the reading of the thermometer may be inaccurate.

Studies

Accuracy specifications by manufacturers of non-contact thermometers are laboratory accuracy, not accuracy in actual use on people being tested for fever. Laboratory accuracy tests do not include important physiological effects which vary from person to person, and setting to setting, rendering no touch thermometers unreliable, regardless of their laboratory accuracy.

For no touch devices, these physiological effects can overwhelm the normal laboratory accuracy of the device, to the point that its actual error is 2 deg C rather than 0.2 deg C.

		Estimated standard deviation of temperature uncertainty
Physiological Variable	Est. Range	No-Touch Thermometry	TA Thermometry
Skin emissivity	0.97 ± 0.02	0.31°C	0.03°C
Skin ambient temperature	±5°C	0.58°C	0.06°C
Variable perfusion on face	±1°C	0.58°C	0.06°C
Perspiration on the face	±1°C	0.58°C	0.06°C
95% confidence interval of errors due to identifiable skin physiological variables		2.09°C	0.21 °C

 

This discrepancy in accuracy was clearly observed during the SARS epidemic in 2003. Exergen, recognized as experts in this field, was asked to provide the underlying science in a study regarding this accuracy discrepancy at a Symposium in 2004, which was subsequently published. The chart above is from that published study, and shows that the errors due to physiological effects is +/- 2.09 deg C.,compared to the light contact method of temporal artery (TA) scanning error of +/- 0.21 deg C. The TA thermometer was specifically designed to overcome these physiological barriers to obtaining accurate readings, and were awarded numerous patents on the design. (Pompei and Pompei 2004). Subsequent studies confirmed the Pompei findings of 2004.

In 2009, Bitar et al. reviewed 6 studies of fever screening with non-contact infrared thermometry (NCIT) devices, such as thermometer guns and thermal imagers. Across the reviewed studies, the sensitivity of NCIT ranged from 4% to 90% and its specificity ranged from 75% to 100%. In other words, NCIT detected fever in from 4% to 90% of the people with fevers, and NCIT did not detect fever in from 75% to 100% of people who lacked fever. The extremely wide range of reported sensitivities (4% to 90%) suggests generally poor usefulness of the NCIT methods, both because values at the low end of the range are unacceptably poor (4% of fevers detected), and because it is difficult to recommend a technology for which the user cannot tell if they will receive good (90%) or disastrous (4%) performance. https://www.eurosurveillance.org/content/10.2807/ese.14.06.19115-en

In 2019, Mouchtouri et al. reviewed the real-world efficacy of fever screening at airports and borders, and found that almost no disease cases had been caught across several nations and pandemics. The screenings were primarily performed with thermometer guns and thermal imagers. https://www.mdpi.com/1660-4601/16/23/4638

It is now common knowledge in the professional medical community that non-contact thermometers are too inaccurate to use as a reliable screening device for fever, and are used largely for theater effects. An August 13, 2020 article in Forbes magazine quotes Dr. Anthony Fauci, director of the National Institute for Allergy and Infectious Diseases, as saying, when referencing infrared thermometers that take a person’s body temperature by aiming the device at their forehead, “We have found at the [National Institutes of Health] that it is much, much better to just question people when they come in and save the time, because the temperatures are notoriously inaccurate many times.”

• Fauci Says Coronavirus Temperature Checks ‘Notoriously Inaccurate’
• Coronavirus temperature scans are nothing more than pandemic security theater. In some cases, they're dangerous.
• More Marketing than medical evidence: infrared thermometers to screen for COVID-19

Without peer-reviewed published clinical studies, non-contact thermometers commonly available cannot be relied upon for medical accuracy in fever detection.

Accuracy of Exergen Temporal Artery Thermometers

With more than 100 published peer-reviewed clinical studies attesting to the accuracy on all ages from newborns to geriatrics, in all settings where fever detection is needed, the Exergen temporal artery thermometer is by far the most proven accurate, compared to thermometers which have no or very few clinical studies. Learn more about the accuracy of temporal thermometers.