Pros and Cons of Fever Scanning
In the age of COVID-19, does it make us safer?
With the advent of COVID-19, the topic of fever scanning has exploded on the Internet. It’s a popular topic in the media and vendors are developing new solutions to capitalize on the opportunity. I’m going to explain what temperature scanning is (and isn’t!) and give you a basic understanding of how it works so you can make your own decision about if it’s worth it.
Fever Scanning 101
The core concept is something we are all familiar with — using a thermometer to see if someone has an elevated body temperature (EBT). An EBT, or fever, is one indication that your body’s immune system is fighting an infectious agent, such as a virus or bacteria. For live event venues, the idea is that refusing entry to guests who have a fever can help prevent the spread of disease and reassure visitors that the grounds and venues are safe.
This isn’t a perfect solution. Some people can have an EBT for other reasons — maybe they had to stand in the sun before entering the venue. Cold weather outside or even over the counter pain medication such as aspirin may mask real fever symptoms. More importantly, many people with COVID-19 are asymptomatic and will not exhibit a fever. The World Health Organization estimates that as many as 80% of cases are mild or asymptomatic entirely.
Different Methods of Fever Scanning
Every fever scanning product and technology that is being talked about today can be put into three categories based on the core technology used. They all have pros and cons and each might be the right solution for different use cases. The key things to consider are accuracy, cost, and usability.
Traditional Medical Thermometer
Medical thermometers are familiar to everyone. They are inexpensive, accurate, and easy to use. They are available from many different sources both online and at any corner store. Both contact and non-contact versions are available.
The downside is that you must hold the device very close (2–3 cm or 1 inch) to a guest’s forehead and then wait to get a reading. The employee has to be in close proximity to a potentially sick person and the overall process is very slow and tedious. While these devices are generally available, they are intended for home use, not large-scale venue use.
Thermal Cameras
On the other end of the spectrum, there are many different solutions using thermal cameras. A visible light camera is built with pixels that are sensitive to regular visible light in a manner very similar to the human eye. A thermal camera, on the other hand, is built with pixels that are sensitive to heat, giving a thermal view of a scene.
It is important to understand that thermal cameras are mostly used for industrial equipment. They don’t have to be accurate for these tasks, and inexpensive thermal cameras are typically accurate to +/- 2 °C, (+/- 4 °F) which is not sufficient for EBT detection.
The main vendor of thermal cameras, FLIR, sells only one FDA approved thermal scanner and it is very expensive. Some vendors claim they can detect EBT from people in motion walking past a thermal camera. Both the FDA and FLIR recommend against this, saying that subjects should come to a complete halt and remove glasses for an accurate EBT thermal reading. If a subject has to come to a halt anyway, most of the advantages of a thermal camera are lost.
Temperature Guns
Temperature “guns” are contactless devices developed to measure the surface temperature of something at a distance, and some can measure temperatures a hundred feet away or more. This sounds like the perfect solution, but they are built for industrial use, not people. Any device that has a wide temperature range has an advertised range of from -22⁰ F to 752⁰ F — is not going to be appropriate for detecting human temperature.
Is Fever Scanning Worth It?
Because most sick people will voluntarily choose not to attend live events and anyone who wants to attend while sick can mask their fever with over the counter medication, fever scanning isn’t particularly useful for live events. Because each employee can potentially come into contact with a large number of guests and there is some motivation to come to work while sick, it may make sense to check employees for a fever at the beginning of each shift.
A word of caution: not only is this solution not perfect, there are a lot of people and companies racing to build systems that will address the new demands caused by this pandemic and they are not all created equal. Companies are claiming that they can “detect 1,000 COVID infections an hour”. Obviously, no thermometer can detect a COVID infection — the best any of them can do is to detect an elevated temperature which might be an indication of some sort of illness. There are also a large number of manufacturers of temperature guns promoting their devices as fever scanners, even though they are not accurate enough for this use case.
None of these solutions are perfect. Depending on a myriad of human and environmental factors, measuring body temperature will generate false positives (people who appear to have a fever but don’t) and false negatives (people who have a fever but don’t register). Many devices on the market are too inaccurate to be used for EBT scanning at all. Also, they can’t detect COVID-19 (or any pathogen) directly, although it is safe to say that anyone with an EBT should probably be turned away from a live event. To me, fever scanning goes into the category of security theater — it might make people feel safer but it doesn’t little to actually increase safety.
Mary Haskett is CEO and co-founder of Austin, Texas-based Blink Identity.
