Infrared thermometer not accurate enough

Dr See says the infrared thermometer is fast and convenient, but the quality and the accuracy depend on the distance-to-spot ratio


INFRARED non-contact thermometers, made popular as a means of checking for fevers — a symptom of the coronavirus — are unreliable due to their low accuracy and inability to measure internal temperatures, according to an expert.

“The infrared thermometer has good points. It’s fast and convenient, but the quality and accuracy of this depend on the distance-to-spot ratio.

“For example, if somebody takes the infrared thermometer slightly further in distance, the temperature becomes lower,” Osel Group medical director and chief clinical and innovative scientist Dr Kris See Ke Shyang told The Malaysian Reserve (TMR) recently.

To measure one’s temperature, one should always try to measure at a safe distance which is ambiguous as this is up to individual interpretation, he added.

Usually, the rule is to keep the thermometer gun one foot away from the surface to be measured.

“Now, in supermarkets and shops, people taking the temperatures are security guards and foreign workers and many of them are not properly educated regarding this.

“I’m just very surprised that ever since the onset of the Covid-19 pandemic, nobody has talked about it,” Dr See said.

Fever, dry cough and fatigue are the most common symptoms of Covid-19, which has killed over 312,000 people and sickened 4.64 million worldwide.

In Malaysia, temperature testing has become commonplace at most public spaces including offices, shopping malls and commercial spaces, as a means of preventing potential Covid-19 carriers from spreading the deadly virus.

Dr See said the infrared thermometer has an accuracy of plus-minus three degrees, which is inadequate and inaccurate.

“Amid the Covid-19 pandemic, people everywhere are demanding for this thermometer. It is very difficult to prevent unscrupulous business people from buying low-cost infrared thermometers at a cheaper rate so that they can maximise the benefit.”

He added that the infrared thermometer only measures the surface and not the internal temperature.

“So, it’s really just a general screening tool. You cannot with very high accuracy say if somebody is having a fever or not,” he said.

According to Dr See, doctors do not diagnose Covid-19 based solely on temperature but also on exposure, risks and other symptoms.

He recommends that people obtain an approved pharmaceutical or medical grade infrared thermometer rather than cheaper alternatives.

Although the prices of such thermometers are “at least 10% higher than normal”, these devices are worth the money as they are accurate and can last a long time.

On whether the usage of infrared thermometers will compromise health standards, Dr See said such devices can be used if they are approved by engineering, medical and pharmaceutical standards, despite being less accurate than ear thermometers.

“I think that in an ideal situation, certainly everybody wants the best, but this is a crisis and we are still not out of the woods yet, so we need to be practical,” he stated.