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How Thermal Camera’s can be applicable for Fever Screening
ABSTRACT
Thermography is a useful tool to conduct non-contact mass fever screening in a cost-effective and most efficient way. It was proven effective during the first outbreak of the SARS (Severe, Acute Respiratory Syndrome) epidemic when the virus swiftly spread throughout different continents resulting in around 8,000 infected cases. Thermal fever screening has been implemented to detect a potentially affected person that may be a carrier of the disease.
Over the period, different companies had developed various tools that may be used for fever screening. However, some of them still fail to provide appropriate fever screening today. We see several videos of different products. They may all have the same functionality, but the accuracy of each device will differentiate them from one another.
Conventional fever screening with the use of a battery-operated thermometer may usually provide inaccuracy in getting body temperature, especially when it is used continuously. In some instances, if a person is not aware of what is the average body temperature, the possibility of missing out on a potential virus carrier is strong. Compare to a full solution with the use of a Thermal Camera; the assigned person is not required to have any physical contact for both people. Advanced Thermal Solution, like Immunotherm, is designed for heavy human traffic wherein people do not need to stop at a particular pint to be screen.
How did Immunotherm start
Digital Thermal Power is a local company established in Dubai, UAE, that specialized in building inspection services and an authorized FLIR distributor in GCC. Skilled Engineers and Thermographer run the core business of the company. In August 2019, the company started to develop different solutions using thermal cameras. One of them is Immunotherm for mass fever screening. Since then, the solution had learned to adapt to varying types of environments and identify each difference between human body features. Today, Immunotherm is the first-ever solution developed in the United Arab Emirates that has been implemented throughout Gulf Countries screening each passenger, office workers, students, factory workers, and more.
Understanding how Immunotherm works and limitation of Infrared
Accuracy in terms of temperature reading using infrared may differ since they are some factors that may affect temperature accuracies such as human, environmental factor, and equipment variable. It is also limited by the fact that the thermal device measures skin temperature and not the core body temperature. Therefore, each thermal imager should be able to understand febrile from a healthy subject and by knowing how his device works.
Human factor:
- When a person is just starting to have a fever, fever may not be significant enough to reach the set minimum target for temperature detection.
- Individuals’ activity each person has different activities, i.e., the temperature may be affected by the food that we take; it may increase and decrease your temperature.
- One thing everyone should know Infrared does not detect the presence of influenza in our body. During the subsiding stage of being febrile temperature can return to normal, either gradually or suddenly, but at this stage, the pathogen is resolving
The usual incubation period for influenza is at least two days depending on the strain and on the person infected. Still, usually, it can be contagious 24 hours before the onset of the symptoms.
Environmental Factors
Infrared detects infrared radiation, and human skin absorbs radiation that may come from the sun if a person is exposed from direct sunlight in a long period, this may affect the accuracy. Since Thermal camera usually measures the temperature o a surface of an object by interpreting the density of an infrared signal emanating from that surface and reaching the camera itself. Fever screening is not valid when used outdoors since it cannot be positioned to direct sunlight, outside lights, reflective lights. Ambient temperature is central to the controlled environment. Temperatures too warm or too cold for comfort (18°C to 24°C is optimal, and ISO recommended) can affect the accuracy of the target temperature reading.
Device Variables:
Each thermal camera has an individual specification to provide an accurate reading for elevated body temperature.
NETD (Noise Equivalent Temperature Difference) is closely related to thermal sensitivity. The very minimum to avoid thermal noise is NETD of 100mK (0.1°C), but nowadays, we have an expectation of 50mK with the ability to detect temperature differences of 0.05°C. The ideal spectral range is 7.5 to 13 microns.
In addition, ISO has established technical guidelines for the application:
The device should carry out a self-correction (NUC), and it must operate in near real-time for rapid screening.
Currently, most qualifying thermal devices on the market are Focal Plane Array microbolometer technology with resolutions of 320×240 or 640×480 with 30-60 frames per second.
This knowledge is critical to effective screening, the International Organization for Standardization published ISO 13154:2009 with operational and implementation guidelines for screening thermography.
ISO Functional Requirements:
- Detect infrared radiation emitted from the FACE over at least the range of 30°C to 40°C
- Obtain a temperature reading from the TARGET (between the eyes)
- Compare that temperature reading to the THRESHOLD TEMPERATURE to determine if the person is febrile.
- Isothermal color display for visual interpretation and rapid identification of the target
- Indication of temperature range, with color code/temperature scale, shall be displayed.
- The screening thermograph shall be provided with at least one-color mapping mode where the colors follow the order of the visible spectrum such that blue is cooler and red is hotter.
- Date and time that the image was acquired
- Display THRESHOLD TEMPERATURE
- Create a thermogram of the FACE. A guide or mask shall be provided in the image of the WORKABLE TARGET PLANE on display.
- The image shall be provided with an ALARM SYSTEM that includes an alarm that indicates when the THRESHOLD TEMPERATURE has been exceeded inside the TARGET.
Significant areas of your measurement
The human body is a good object when it comes to emitting radiated heat/energy, but the temperature from a human head to toe may span a minimum of 8 C° on an average person. The human head is the hottest, and feet are the coldest, and there are variations in temperature within each region.
Normal temperature ranges
In adults, the average core body temperature (referred to as normothermia or afebrile) is 36.5–37.5ºC or 97.7–99.5ºF. A wider temperature range is acceptable in infants and young children and can range from 35.5–37.7ºC or 95.9–99.8ºF.
And since the human skin absorbs radiation, i.e., from the sun, this may affect your temperature reading. Immunotherm is specialized to detect basal body temperature, and the common target area will be the Inner canthus of the eye: close to the brain and hypothalamus where a branch of the carotid artery terminates. The ideal area to measure EBT, but the target size is only 5-6 mm (the most stable and convenient area for measurement).
The second area will be your Ear Canal One of the best places: several arteries flow to the hypothalamus, which regulates body temperature; however, since this is within the inner part of our body, we can only see the outside of the ear canal. For precaution, you may ask a person t double to check their temperature when captured with a thermal camera.
Requirements for screening the face
The face should be free from any obstruction such as eyeglasses or any eyewear that may cover the inner canthus. It is essential to know that the IR camera cannot see through the glass; therefore, the reading you might get when a person is wearing glasses is just a reflective temperature. Other IR cameras with fever screening solutions don’t work when a person has too much obstruction from their faces, especially nowadays wearing masks is a must. However, for Immunotherm, it designed to do still the detection even a person wears a mask or any headdress. Since Immunotherm is developed in UAE, we created the software to continuously detect the temperature of a person regardless of wearing Kandara’s or abaya.
Where to position your Thermal Camera
One primary reason why most of the airports, malls, and hospitals choose mass screening solution is to decrease the traffic when taking body temperature. Having an answer for fever screening keeps the flow of human traffic without any delays. Most of the people who purchase thermal cameras do not know where they are going to install the camera. Knowing the right place where to connect the camera is essential because the thermal camera will be your tool for preliminary screening.
A thermal camera must be positioned to be pointing directly in front of a person, and it should be raised high enough to measure each person’s height, for example, a kid, adult, and a person in a wheelchair. Thermal cameras are built with a different resolution. If a camera has a higher resolution, the more distance it can measure, but if it has a low resolution of 80 x60, the maximum length is only at 2 meters. It is not advisable to be mounted on a ceiling. Your thermal camera should not also be in any area that person may accidentally hit at any time in positioning your thermal camera always consider that traffic flow must include an easy exit.
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