Frequently Asked Questions: Thermal Imaging for Elevated Skin Temperature Screening

Thermal imaging cameras and scanners can be a useful, efficient tool for screening people for signs of elevated skin temperature (EST).

Q: Can products be used to detect a virus such as the Novel Coronavirus (COVID-19)?

A: No, thermal imaging cameras and scanner cannot be used to detect or diagnose an infection. However, they are used today in public spaces such as airports and hospitals. It’s also used by essential services such as manufacturing and shipping as an effective tool for measuring skin surface temperature. People who are identified as having an elevated skin temperature can then be screened by medical professionals using additional tools such as an oral thermometer.

 Q: How does thermal imaging technology work?

A: Thermal cameras and scanners detect heat radiation and can be used to identify the surface temperature of objects and people. With this capability, thermal cameras are commonly used as a non-contact screening tool to detect differences in skin surface temperatures and pattern changes.

Q: How accurate are the thermal cameras and scanners?

A: Thermal cameras “see” or detect the temperature differences with temperature measurements between -20°C and 2,000°C (-4°F—3,632°F). The standard (FLIR) product accuracy specification of ±2°C or 2% of the temperature reading at 30°C (86°F) ambient environment applies to all temperature ranges it measures and for the multiple applications for which it can be used. FLIR thermal camera with Screening mode can achieve accuracies of ±0.5°C (0.9°F) at 37°C (98.6°F). This can be achieved by using the camera in a stable ambient environment, only looking at humans, and updating the reference samples according to the population being screened. For scanners (Dahua Thermal Scanners) offers remote non-contact temperature monitoring with high temperature measurement accuracy (±0.3°).

It’s important to note there are many factors that can affect the accuracy of thermal cameras, such as focus, distance, the emissivity* of the target, the ambient environment, and the speed at which the temperatures are acquired. 

*A target’s emissivity is its ability to emit thermal radiation. For example, ceramic mugs, clothing, and even human skin have high emissivity, while polished metals have low emissivity.

Q: How close do you need to be to detect someone with an elevated temperature?

A: In order to obtain a good temperature reading, it is recommended that the intended target be as close to the camera as possible (with respect to the camera’s minimum focus distance). The location of the camera may require a different lens. Distance to the target is an important consideration, as is focus.

It is important that the application be set up so that all intended targets are in focus during the screening process, thereby creating a good image. In addition to focus, a good image is dependent on several additional functions and settings, with certain functions and settings affecting the image more than others. Functions and settings that the operator needs to set and/or adjust include the following:

  • Adjust the infrared camera focus
  • Adjust the infrared image (automatically or manually)
  • Select a suitable temperature range
  • Select a suitable color palette
  • Change the measurement parameters
  • Perform a non-uniformity correction (NUC)

 

Q: Do I need to use a black body for EST screening?

A: There are advantages and disadvantages to using a black body when screening for elevated skin temperatures. Including a black body in the camera’s field of view can improve the system’s performance in this application.

In contrast, using a black body for elevated skin temperature screenings can create challenges. The first is the cost and complexity of including an additional piece of hardware in the solution. Black body integration into a system makes mounting, powering, and ultimately maintaining it more complex. Such an addition also introduces another potential point of failure into the overall solution.

Proper focus on the black body is essential to getting accurate measurements. For a black body to be effective, it must be mounted in the same plane as the person being screened. A black body that is significantly closer or farther than the person being screened will be out of focus and not function as an accurate reference source.

Q: How should operators use thermal cameras for skin temperature screening?

A: Here are several tips to ensure optimal measurement performance from a thermal camera:

  • Camera operators should screen people one at a time to look for temperature anomalies.
  • Camera operators should measure temperature at the tear duct (inner canthus) as this location provides the closest temperature correlation to human core body temperature.
  • A camera operator who detects elevated skin temperature in a person being screened should request that such individual be screened using a device designed specifically for measuring body temperature, such as a thermometer.

 Q: Do people using your cameras need to be certified/trained to understand how to interpret the images and data?

A: FLIR recommends that thermal camera operators obtain at a minimum Level 1 thermal imaging certification through certified thermography courses such as the Infrared Training Center. This is not a medical training or medical certification, but it provides a baseline understanding in thermography. The Infrared Training Center offers more advanced training. More information can be found at www.infraredtraining.com.

 Q: Can you name some companies, organizations, and airports that have purchased your products?

A: While we cannot name specific customers or comment on current sales, we can say that our thermal cameras are used by customers at ports of entries and high-traffic locations in several countries, including the US, China, Hong Kong, Taiwan, Singapore, South Korea, Thailand, Philippines, and Malaysia.

 Q: How long had been thermal cameras and non-contact thermometers for elevated skin temperature screening been used?

A: Thermal cameras and scanners for skin temperature screening were used during the SARS outbreak in 2003.