Crowd temp screening is a joke, one tech expert says

Thermal Infrared Camera crowd scanning
With no one in a crowd in the ideal focus position of a thermal camera used for temperature screening, one expert says it's no more accurate than having someone put a hand on your forehead and guessing your temperature. (Credit: asiandelight/iStock/Getty Images Plus)

Markus Tarin, President & CEO of MoviTHERM, a developer of thermography inspection solutions, has spent the last two decades developing thermal imaging systems for industry and research. But never in his career—not even during the SARS outbreak in 2002—has he seen so many companies jumping into the market with essentially unvetted temperature screening solutions.

The fact that the FDA released a temporary non-binding relaxation of its requirements in order to increase availability and capability of imaging products during this health emergency might seem to have only fueled the frenzy. But Tarin said that the gold rush started even before the announcement.

“It’s like the Wild West out there,” Tarin said. “At this point we have counted over 52 companies that have joined the space. Demand is being driven by every organization’s desire to put something in place to make people feel comfortable as they go back to work.”

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Tarin said that he understands that the pandemic has created an extraordinarily tough business climate for companies. He even has a kind of grudging admiration for the entrepreneurial spirit of some companies rushing to market with an array of thermal camera technologies.

“I admire how quickly some of these companies have been able to innovate and adapt, and I can really appreciate the intent. But at the same I find some of these solutions really unethical,” he said.

While not all are unethical, he noted that at worst some marketing claims are grossly exaggerated, with some companies slapping a cheap camera on a system and selling it for $1,500.  A good system will cost around $10K, if as Tarin notes "You want to take temperature scanning seriosly."

At best, some technologies fall short in meeting recommendations. In particular, he emphasized, “There is no viable crowd scanning solution available today--as defined by more than one person in the image being scanned simultaneously--that can properly measure elevated body temperatures.”

Richard Hames, sales director for Thermoteknix, disagrees with that assessment. His company sells the FevIR Scan Fever Screening System for mass screening of high pedestrian areas, with hundreds of installations in environments as diverse as airports and banks and hospitals.

“Since 2003, we have been producing these systems in applications for organizations that want to typically scan more than 200 people and measure elevated temperatures, and these systems are probably more sensitive than they were when the guidelines were developed. So, there’s two different ways to think about it – go strictly down the path of the guidelines or implement the technology in a different, more efficient way,” he said.

The importance of pixels

An infrared, IR or thermal imaging camera works by detecting and measuring the radiated infrared energy from the surface of an object. This data is then converted into a temperature reading. The more detector elements, or pixels, a device has, the higher the resolution of the image and the more accurate the temperature measurement.

The further the camera is away from the object being measured, the more the pixels are spread out over an area, and the lower the image resolution—and therefore the less accurate the measurement. That’s important, because even a small temperature difference could be the difference between a normal or elevated reading.

The accuracy of a thermal camera depends on many factors, including temperature drift, emissivity, and humidity and even under ideal conditions the accuracy is no better than plus or minus 2 deg C. Throw people into the equation and it makes things even more complicated.

“Understand that we are not looking at an innate object like a piece of steel,” said Tarin. “The human body is a complex, closed-loop mechanism that will change and fluctuate its surface temperature based on things like ambient conditions, the amount of energy expended, even alcohol consumption.”

Compensating for elevated body temperature measurements can involve either a relative comparison of skin surface temperature or an external black body reference, which can increase the measurement accuracy to about plus or minus one-half of a degree C.

The Centers for Disease Control consider a person to have a fever when the temperature measured is 100.4 F or 38 C. If a thermal camera found someone with a 35.9 C reading under most methods, the accuracy could be off enough to miss entirely someone with an elevated temperature

Fielding dozens of calls per week from companies inquiring about temperature scanning systems and how they work, MoviTHERM put together this video

The trouble with crowds

Point the camera into a crowd to perform temperature screening, though, and things get even more challenging.  “Scanning a crowd means that some people are closer  in and some people are further away from the camera, which means that nobody is in the ideal focus position of the camera,” said Tarin. 

According to FDA Guidelines, the ideal way to obtain an elevated body temperature reading is by measuring the surface temperature of an individual's inner canthus (tear duct), which should be covered by a sufficient number of pixels to allow for accurate measurement (a minimum of 3 X 3 pixels to 5 X 5 pixels, ideally more.) The individual should remove any eyewear and be standing a fixed difference (as per the manufacturer's recommendations) from the camera.

Without those procedures, Tarin said, “At best you are getting the head temperature, which is no more accurate than a nurse putting a hand to someone’s forehead and taking a guess.”

Hames acknowledges there are standards that refer to the camera system itself and its accuracy and other standards on how they should be used, noting the World Health Organization. But he adds that many of his customers want to use the technology a different way. “The World Health organization standard says that a person must take their glasses and head coverings off and come up and stand a certain distance for a couple of seconds and have their temperature taken, but that means you can only scan 15 or 20 people a minute, it’s a much slower process.”

Speeding up the throughput does require a tradeoff. When you have a group of people filing past the camera, some will be wearing sunglasses and head coverings so the system will focus on the forehead, said Hames. “While this results in a less accurate measurement than using the eye duct, we are able to account for that in our temperature reference and software. In the end, what you are looking for is an elevated temperature.”

Tarin might take issue with that, as he says that the optics and physics don’t lie. According to his calculations, pointing a camera into a crowd to detect an accurate, elevated body temperatures would require a thermal camera with >12 megapixels, which does not exist today

In the end, the real question to ask is, "What is the intended purpose of temperature scanning?" A thermal camera can only detect, measure and document the variations in skin surface temperatures. Its role in combating COVID-19 is limited, as only a health care professional can make a diagnostic determination.

“Are you just deploying this gear for ‘feel good’ needs, or are you truly looking to measure and eliminate feverish people?” said Jack E. Gold, President and Principal Analyst of J.Gold Associates, LLC. “You can deploy and tell people that you are doing the right thing by measuring their temperature. They won’t know if it’s true or not, of course, but they may feel better about going to your facility.

“But with no regulations that I know of to verify things are being done accurately, I could deploy a witch doctor that says he can tell your temperature is not normal by looking at your nose--and that might be just as accurate”

In his opinion, if you can’t do it right--don’t bother.

MoviTHERM has a number of useful educational resources on temperature screening for COVID-19 on its website, including:

Coronavirus - Screening for Elevated Body Temperature

Elevated Body Temperature Screening - Read this, Before Buying a Thermal Camera

RELATED: Thermal camera checks body temps and provides security

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