Thermal cameras are terrible at exposing COVID-19. Here’s why companies are buying them anyway

Companies are increasingly turning to tech to help mitigate the spread of COVID-19 among their workers. Individually, these technologies provide limited help, but together they may keep workers vigilant about their health.

Thermal cameras are terrible at exposing COVID-19. Here’s why companies are buying them anyway
[Photos: USGS/Unsplash; Brooke Cagle/Unsplash]

When Suffolk Construction first installed thermal cameras on their jobsite in Hollywood, Los Angeles, all the workers wanted to see what their faces looked like in yellow, red, purple, and blue. These are the colors that indicate warmth, coolness, and potentially a fever.


The new technology is part of an evolving infrastructure aimed at keeping workers protected from COVID-19. Companies like Suffolk are buying up a range of cameras, applications, and even robots to mitigate virus transmission. While such precautions may be helpful, they are far from a panacea—even though some companies treat them that way. COVID-19 has been a particularly difficult virus to curb in part because of its long incubation period and high portion of asymptomatic cases, making it hard to detect even with technology.

Daniel Garay, a safety manager for Suffolk’s Hollywood site, says the thermal cameras are one of the most recent additions. In February, his company started circulating paper surveys to determine whether workers were experiencing any coronavirus symptoms before they came into work. By mid-March, Suffolk had created and launched an application that screens workers through a questionnaire for potential COVID-19 infection. The questionnaire asks whether they have experienced symptoms or were in proximity to someone who tested positive. The company also encourages workers to stay home if they’re sick and offers varying paid leave packages, even for subcontractors. Suffolk also allows workers to work from home when possible.

The federal government considers construction an essential business. While some of Suffolk’s projects are more ordinary fare, like building hotels, some of its work is directly related to COVID-19. In Boston, the company worked with the city to convert the Boston Convention Center into a 1,000 bed field hospital. There can be more than 400 people on a jobsite at a time. So far, the company has rolled out 50 thermal cameras to jobsites around the country. Suffolk plans to deploy them in its offices next.

The first hiccup we ran into was a guy who had a mouth full of coffee.”

Daniel Garay

On Suffolk’s construction sites, workers must complete their health survey before they arrive. Cleaning crews come onto the site first to disinfect the area. Worker start times are staggered. When workers get to the site, they go through the thermal camera check to see if they have an elevated temperature. The camera uses the inner corner of the eyes to gauge elevated body temperature. When the camera is initially set up, the operator has to take the temperatures of 10 fever-free people for the machine to gauge a mean temperature, which is then used as a baseline check when the camera is up and running. If a worker shows a temperature three or four degrees above the average temperature, they go through a secondary screening process where they’re asked questions about their health. The company will then make arrangements for the worker to get further care from a physician if needed.

The workflow has not been without its missteps.


“The first hiccup we ran into was a guy who had a mouth full of coffee,” says Garay. One worker had taken a swig of hot coffee right before stepping in front of the camera, sending off alarms. “We told him he had to step aside and wait ’til [he] swallowed that coffee.”

The limitations of thermal cameras

Thermal cameras were not originally designed to detect fevers. Before COVID-19, they were used predominately by the military for everything from detecting faulty electrical systems to charting proximity to other ships at sea. “In normal times, people aren’t beating our door down for elevated skin temperature solutions,” says Chris Bainter, global business development director at FLIR Systems, one of the biggest makers of thermal cameras. “We have some demand, mainly in Asia Pacific, for travel and transport.”

Still, he says, pandemics have been spurring sales of thermal tech since 2003, when SARS emerged. FLIR has seen sales spikes during MERS, H1N1, and Ebola outbreaks. Typically, these taper off over time, but Bainter thinks that COVID-19 has incited a new behavior in the commercial market. “Frontline screening will become the new normal,” he says. 

Frontline screening will become the new normal.”

Chris Bainter

Though they are already being deployed, thermal cameras are limited in their ability to detect fever. Skin temperature registers a bit cooler than inside the mouth. While an oral thermometer might capture a 98-degree temperature, FLIR’s camera might register a skin temp of 95 degrees. They are not exact corollaries. While thermal cameras may be fairly accurate in their ability to determine skin temperature, they cannot discern the nuances of why a person may have a higher or lower temperature reading than average.

A person who is bald recently told me that they consistently get lower temperature readings on thermal cameras because they don’t retain heat as well. External temperature might also be affected by other non-COVID-19 ailments. Skin is also more susceptible to environmental factors, like if a person is sitting inside of a hot car for a prolonged period of time. Fever suppressants, like Tylenol, could also help a person evade detection.


Having screening measures in place is a critical component of bringing workers back to work. Already, Suffolk, General Motors, City Farmers Markets, and others have sought to implement thermals cameras as part of their effort to mitigate COVID-19 among their employees and customers. Using thermal cameras is an attractive option to companies because they are relatively affordable. FLIR’s thermal camera systems, for example, start around $6,500.

Businesses are desperate for ways to identify an illness among their workers that in some instances has no signals at all. However, reports on such cameras show they are not particularly effective at finding sick people in a crowd. A 2019 study looking at the use of entry and exit screening at airports found that entry screening was not effective for locating people who had contracted Ebola, H1N1, and SARS. When people were flagged by the system, they were often found to have other unrelated illnesses, such as a respiratory infection or a more mild influenza. This is in part because the symptoms for the diseases under scrutiny were not easily observable.

Systems like FLIR are only capable of observing severe temperature. The problem with COVID-19 is that most cases have mild symptoms or none at all. On top of that, it has a long incubation period: A carrier can have the illness for 14 days without showing any signs. Relying on thermal cameras as the sole screening measure for rooting out coronavirus in crowds or workforces would be a failing proposition.

From thermal cameras to social distancing tech

Suffolk has tried to make cases of COVID-19 among its workers more visible by trying lots of different solutions. Not all of them have worked. For example, the company tried using proximity detectors to maintain social distancing. “It would go off at weird times when no one was on the jobsite,” says Alex Hall, an executive at Suffolk.

It would go off at weird times when no one was on the jobsite.”

Alex Hall

Now the company is working with a company called Tri-ex on helmet-mounted devices that start beeping when two people get within 8 feet of each other. The sound gets louder as people get closer, and can also be muted as needed. The devices record moments of proximity, so the company can send a manager over to see why workers are making prolonged contact. However, the system is limited in that the data is only reported back to a manager when the device is near a base station. Suffolk is currently considering contracting with robot maker Boston Dynamics to attach a base station to its quadruped Spot, so it can rove around the site and report back data in near real time.


Hall says his company is also looking at robust ways it can collect more information on whom its workers are coming into contact with.

“Everything we do about social distancing on the jobsite doesn’t matter if people are coming to work on mass transit or in a car pool,” says Hall. The company is in the process of launching a new application that would ask employees to divulge more data about their day-to-day activities to understand their COVID-19 risk. In addition, the application would offer workers who have been diagnosed with COVID-19 a step-by-step manual for how to manage the illness and keep in touch with care providers. It would in effect allow the company to contact-trace COVID-19 within its ranks.

Such tracking raises big questions about employee privacy. The American Civil Liberties Union has cautioned about the limits of using cellphone towers and GPS technology to detect a person’s whereabouts within the 6-feet guidelines. There are also concerns about the ways employee data will be retained, stored, shared, and used.

Hall notes that while overall the company’s system seems to be working, there have been instances where Suffolk has had to shut down jobsites for 48-hour deep cleanings after a worker tested positive for COVID-19.

“[It’s] obviously very difficult to deal with an absolute unknown entity,” says Hall. “We can have all these physical controls in our workplaces and someone can still be asymptomatic. So for us it’s just important to be sharing as much information as possible.”

About the author

Ruth Reader is a writer for Fast Company. She covers the intersection of health and technology.