Don't Be Fooled By Hot Water Bottle Fever Camera DemosBy: Ethan Ace and John Honovich, Published on Aug 24, 2020
Fever camera salesmen like to fool buyers (and themselves) with hot water bottle demos. It deceives and detracts from the real flaw - these systems miss real human elevated temperatures. Learn how / watch now:
What's clever is that many people see it and think "Wow, this thing works. No water bottle, normal temperature. Hot water bottle, alarm!"
Common Sales Tactic
The hot water bottle is the go-to move of fever camera marketers around the world such as Dahua, Hikvision, and Sunell, examples shown below.
Problem: Too Hot
The problem is simple, hot water can be really hot - 110°F, 120°F, etc. Just because a system can detect a 110°F bottle does not mean that it can accurately detect 100°F or 101°F, the real temperatures that humans would actually be with a fever.
Your system needs to be precise enough to distinguish between 98°F and 100°F, a much harder task than the fever camera salesman who wants to fool you with a water bottle of 110°F vs 98°F.
Solution Just Hot Enough
If you really want to see if a system works, you want to elevate your forehead temperature just hot enough to replicate 100°F or 101°F, the temperatures that actual humans with fevers have. A person with an actual 110°F body temperature is not going to be walking through anyone's entrance.
Here is how to do it:
Warm one's forehead with a rubber water bottle / pouch:
The aim is to heat one's forehead modestly. You want it to get to 100°F to 102°F to fairly emulate a 'fever'. This depends on how hot the water inside the pouch is and one can easily experiment with a few seconds to ten seconds to see the right duration to elevate a subject's forehead to the desired range.
Then walk in front of the camera or detector you are testing:
Immediately, have a second person come in with a calibrated hand-held IR thermometer and measure the subject's temperature.
Compare the temperature that the fever camera / detector produces to that of the handheld IR thermometer.
This way you can compare to ground truth (with the calibrated handheld IR thermometer) rather than simply walking around with a very hot water bottle affixed to one's forehead.
Don't be fooled, use this superior method to better detect accuracy issues. In our testing of 20+ 'fever' devices, we found most systems have issues detecting moderately elevated temperatures, tending to favor reporting back 'normal' / statistically average temperatures, which produces a false sense of safety and risk of infectious people passing inside one's facility.