Q&A's on Thermometer Accuracy

Q: What makes thermometers accurate? What should we know about thermometer accuracy?

A: Published peer-reviewed clinical studies.
Without such studies by medical professionals, there is no assurance of accuracy on children and adults in all settings. Accuracy specifications by manufacturers of 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, which can affect the actual accuracy well beyond their laboratory accuracy.

Published peer-reviewed clinical studies are the gold standard for accuracy, since they include actual use on people in many settings, which automatically includes the physiological effects that vary from person to person and setting to setting. Only these studies can provide the assurance that the thermometer will provide accuracy in detecting fevers for all ages in all settings.

With more than 80 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.

Q: How about non-contact thermometers?

A: Non-contact thermometers are highly inaccurate for detecting fevers, here is why: Accuracy specifications by manufacturers of non-contact thermometers (NCIT) 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 NCIT’s unreliable, regardless of their laboratory accuracy. For non-contact 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



Skin ambient temperature




Variable perfusion on face




Perspiration on the face




95% confidence interval of errors due to identifiable skin physiological variables


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 No Touch 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.

Without peer-reviewed published clinical studies, No Touch thermometers commonly available cannot be relied upon for medical accuracy in fever detection.

Q: Have non-contact thermometers been compared to Exergen TemporalScanner thermometers?

A: Yes, in a new study published in 2020. Independent researchers conducted a prospective observational study on a sample of 265 non-infectious patients at two hospitals. When body temperatures read below 99.5 degrees Fahrenheit, the thermometers showed similar results, but as temperatures rose above that, non-contact scanners’ accuracy decreased. Temperatures were farther apart as they rose. The non-contact scanners missed five out of every six fevers detected by Exergen temporal artery thermometers.

According to the authors, “This is the first study to compare the accuracy of non-contact infrared thermometers (NCIT) to TAT in adult patients. Although mass fever screening is currently underway using NCIT, these results indicate that the NCIT may not be the most accurate device for fever mass screening during a pandemic.”

“During this escalating and unpredictable pandemic, there is one constant in helping to ensure public safety: the ability to accurately screen for fever,” said Francesco Pompei, Ph.D., CEO of Exergen Corporation. “Non-contact thermometers are proven to be inaccurate in measuring core body temperature, yet they’ve been used extensively from the start of the pandemic, giving a false sense of security. In public settings, they are large ‘theater,” and as such their use should be seriously questioned. Only thermometers with extensive clinical studies, such as the Exergen TemporalScanner, can be trusted for accuracy during these threatening times of COVID.”


Medical information disclaimer: this document may contain general information relating to various medical conditions and their treatment. Such information is provided for informational purposes only and is not meant to be a substitute for advice provided by a doctor or other qualified health care professional. Readers should not use the information contained herein for diagnosing a health or fitness problem or disease, and should always consult with a doctor or other health care professional for medical advice or information about diagnosis or treatment.