What do you need to know about thermal imaging cameras?
As businesses, schools, hospitals and sporting venues look to safely reopen in a COVID-19 world, thermal imaging systems will play a critical role in helping to detect and distinguish skin temperature variations in people. Thermal surveillance, a mainstay of traditional physical security and outdoor perimeter detection, is now being deployed to quickly scan employees, contractors and visitors as part of a first line of defense to detect COVID-19 symptoms.
In the coming weeks and months, the security industry will look to implement thermal camera solutions for customers, yet many questions remain as to the differences between different system types and how to properly install thermal imaging cameras. In this Q&A, Jason Ouellette, Head of Technology Business Development for Johnson Controls, answers several of these questions.
Q: What are some of the different thermal imaging solutions available in the market to detect an elevated temperature in a person?
For the general market, there are three types of these thermographic screenings. There is the handheld device, which is typically lower cost, very portable, and very easy to use. Typically, this is a point and shoot type of device, but it requires you to be three feet or less from the person that you're screening, which, in today's world, means the user needs to wear protective personal equipment.
For the general market, there are three types of these thermographic screenings
The second type of solution would best be described as a thermal camera and kiosk. The advantage of this system over a handheld device is this can be self-service. An individual would go up to and engage with the kiosk on their own. But many of these kiosk type solutions have some integration capability, so they can provide some type of output, for either turnstiles, or physical access control, but not video management systems (VMS). Some of the downside of this type of system is that it’s less accurate than a thermographic solution because it does not have a blackbody temperature calibration device and the readings are influenced by the surrounding ambient temperature, called thermal drift. So instead of being able to achieve a ±0.3ºC accuracy rating, this system probably provides closer to ±0.5ºC at best. Some of these devices may be classed as a clinical thermometer with a higher degree of one time accuracy, but do not offer the speed and endurance of the thermographic solution for adjunctive use.
And then there are thermal imaging camera systems with a blackbody temperature calibration device. These types of systems include a dual sensor camera, that has a visual sensor and a thermal sensor built right into the camera, along with a separate blackbody device. This provides the highest degree of ongoing accuracy, because of the blackbody and its ability to provide continuous calibration. These systems can provide much more flexibility and can offer integrations with multiple VMS platforms and access control devices.
Q: When installing a thermal imaging camera system what is the most important element to consider?
Camera placement is critical to ensure the system works as expected, however the placement of the blackbody device which verifies the correct calibration is in place is equally as important. If the customer wants to follow FDA medical device recommendations for camera placement, both the height of the camera and the blackbody as well as the distance between these devices should comply with the product installation instructions. This takes into account the device focal range and calibration parameters in addressing the distance from the person undergoing the scan. Also, integrators should minimise camera detection angles to ensure optimal accuracy and install cameras parallel with the face as much as possible, and again in compliance with installation instructions.
Integrators should minimise camera detection angles to ensure optimal accuracy
The blackbody should be placed outside of the area where people could block the device and located more towards the edges of the field-of-view of the camera. You need to keep in mind the minimum resolution for effective thermographic readings which is 320 by 240 pixels as defined by the standards. To achieve this, you would need to follow medical electrical equipment performance standards driven by IEC 80601-2-59:2017 for human temperature scanning and FDA guidelines. Within that measurement, the face needs to fill 240 x 180 pixels of the thermal sensor resolution, which is close to or just over 50 percent of the sensor’s viewing area typically, meaning a single person scanned at a time in compliance with the standards for accuracy.
Along with height and distance placement considerations, the actual placement in terms of the location of the system is key. For example, an expansive glass entryway may impact accuracy due to sunlight exposure. Installations should be focused on ensuring that they are away from airflow, heating and cooling sources, located approximately 16 feet from entry ways and in as consistent of an ambient temperature as possible between 50°F and 95°F.
Q: Once a thermal imaging camera system is installed, how do you monitor the device?
There are several choices for system monitoring, depending on whether the solution is used as standalone or integrated with other technologies, such as intrusion detection, access control or video systems. For standalone systems, the ability to receive system alerts is typically configured through the camera’s webpage interface, and the cameras include abilities such as the live web page, LED display for alerting, audio alerts and physical relay outputs. When done right, these features will all follow cybersecurity best practices which is important for any network solution today, including changing default passwords and establishing authentication methods.
The ability to receive system alerts is typically configured through the camera’s webpage interface
These types of thermal cameras can also integrate with turnstile systems, VMS platforms and access control systems. This is typically done through the integration of a relay output, activated by a triggered temperature anomaly event on a thermal imaging camera which can then be used for activities such as locking a turnstile, or through access control and video systems to send an email or provide an automated contagion report for contact tracing. These capabilities and integrations extend the monitoring capability above that of the standalone solution.
The camera can be configured to monitor a specific range of low and high alerts. Users can determine the actions that should be taken when that alert exceeds the preset low or high threshold. These actions include things like a bright and easy-to-see LED can provide visual notification through pulsing and flashing lights as an example.
Q: What about system maintenance? Does a thermal imaging camera require regular service in order to operate accurately?
First it’s important to make sure the system is calibrated. This can be done after the unit stabilises for at least 30 minutes to establish the initial reference temperature source known as the blackbody. Calibrations conducted before this warm up and stability time period can throw off accuracy. Also, as part of your system maintenance schedule you will want to perform a calibration check of the blackbody device every 12 months, along with following recommendations of the FDA and IEC. If you install the solution and don’t perform maintenance and the blackbody calibration certificate expires, over time there’s a risk that the device will experience drift and a less accurate reading will result.
There’s a risk that the device will experience drift and a less accurate reading will result
Q: What final pieces of advice do you have for either an integrator who plans to install a thermal imaging camera system or an end user who plans to invest in this solution?
Before you buy a thermal imaging camera check to see if the manufacturer ships the camera with a calibration certificate. Also, become familiar with FDA’s guidance released in April 2020, Enforcement Policy for Telethermographic Systems During the Coronavirus Disease 2019 (COVID-19) Public Health Emergency. This document places thermal/fever products for adjunctive use under the category of a Class I medical devices and subject to its regulatory control. Driven by these regulations and categorisation, users need to understand specifically what is required to meet the required level of accuracy for successful detection.
While thermal imaging camera systems are more complex than traditional surveillance cameras, they can prove to be a valuable resource when set up, configured and maintained properly.