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  1. Applications
  2. Thermography
  3. Indicative fever screening during an infectious disease epidemic

Indicative fever screening during an infectious disease epidemic

Fever detection with contact and infrared thermometers from Trotec

In times of infectious disease epidemics, the early detection of infected persons becomes all the more important. Highly infectious viruses, such as norovirus, SARS-CoV-2 (corona) or even H5N1 (bird flu) don’t respect closed doors, international borders or access restrictions. The pathogens spread across the world during a pandemic and the most important measure to help contain them is the early interruption of the chain of infection by detecting and isolating infected people. Airports, sports stadiums and shopping centres, in particular, as well as schools and universities, are required and encouraged, due to their high numbers of visitors and high rate of pedestrian traffic, to make a reasonable effort to contain the further spread of an acute infectious disease.

Fever screening helps to find infected persons

An important indicator in the early detection of already infected persons is an elevated body temperature, indicative of a fever. Therefore, at the time of a rampant virus epidemic, contact-free fever screenings are performed in many places to quickly and reliably identify people with elevated body temperatures in large groups of people. To enable this contact-free scanning, Trotec offers various measuring devices which can be used in different situations. For example, the XC300 thermal imaging camera or the XC600 thermal imaging camera work to identify potentially ill people, even in large crowds. Professional thermal imaging cameras do, however, also require a corresponding willingness to invest, which is easy to guarantee for daily use at airports, but is often not the case for temporary use at a workplace or for an event area.

Infrared thermometer - the effective alternative for temporary measuring

The handy industrial pyrometer from Trotec is another method of contact-free high temperature measurement. Especially in light of the fact that in times of crisis, contact-free infrared thermometers for human-diagnostic purposes are often very difficult to get hold of or are only available at relatively high prices. Additionally, industrial thermometers usually have a much larger measuring range, which makes them an all-round useful tool for work and everyday life, even if they are not used for human temperature screening.

Quick measuring results in times of crisis

Since fever screening during times of crisis is primarily used for the early detection of suspected cases with an increased risk of infection, and the proper medical assessment of the so-called core body temperature takes a back seat, infrared thermometers from Trotec can also be used for prevention purposes.

Precise measuring results in work and everyday life

Measuring devices like the BP21 Infrared thermometer and the BP25 Pyrometer use an almost identical measuring method to medically approved infrared thermometers and deliver comparable, precise results. Infrared thermometers only actually display the temperature of the surface measured without corresponding correction factors, e.g. the forehead surface, but not the core body temperature, as is the case with devices offered especially for measuring fevers. These work with special calculation algorithms and in a limited temperature measuring range of slightly more than the maximum body temperature, which makes them unsuitable for use outside this measuring range (approx. 34 - 42°C).

The contact-free temperature screening using an infrared thermometer is normally done on the forehead. However, the forehead temperature is subject to fluctuations and depends, among other things, on age, body size, environmental conditions and the current form of activity of the person being measured. If, for example, you sweat after physical exertion, the evaporative cooling falsifies the result more than if you do not sweat. If one comes from a cold environment into a warm one, the forehead will be cooler than normal for a while. This difference can be several degrees Celsius. The core body temperature, on the other hand, does not change but remains almost constant. Even a lighter skin tone can produce different measurement results as opposed to tanned skin.

Therefore, there is no simple calculation or factor that can be used to easily convert the measured surface temperature, known as the body shell temperature, to the core body temperature.

Despite this difference in determining the measured values, industrial pyrometers can also be used to draw comprehensible conclusions about the body's core temperature, taking some points into account.

No matter whether in a security area, workplace, private area or at an admission point: Before an industrial pyrometer is used, consistent reference measurements must be taken using a conventional fever thermometer.

Whichever of the following two reference measurement methods you choose, please always note that each measurement must be carried out on a specific device and cannot be transferred across the board from one device to all devices, since each device has its own measurement errors and measurement uncertainties.

Reference value determination options

Method 1: Determination of the temperature difference

  1. Using a suitable thermometer, determine the actual core body temperature of various test persons of different ages and take several parallel forehead temperature measurements with your pyrometer on each of the test persons. The forehead should be dry. Make sure that the measuring distance to the forehead is not more than 5 to 10 cm. Never touch the forehead of the person to be measured directly to avoid cross-infections. Keep the pyrometer as still as possible during the measurement and wait until the measured value has settled.

  2. Determine an average value from the measured values. For example, if the temperature measured by a clinical thermometer is 36.5°C and the pyrometer measurement is 35.0°C on average, it can be statistically assumed that the temperature measured by the pyrometer is on average about 1.5°C below the core body temperature.

  3. If an alarm limit value can be set in the instrument, for example, assuming 38°C as the reaction limit for an elevated temperature, the alarm in the instrument would have to be set to "36.5°C"

Method 2: Determining a corrective emissivity

  1. Using a suitable thermometer, determine the actual core body temperature of various test persons of different ages and take several parallel forehead temperature measurements with your pyrometer on each of the test persons. The forehead should be dry. Make sure that the measuring distance to the forehead is not more than 5 to 10cm. Never touch the forehead of the person to be measured directly to avoid cross-infections. Keep the pyrometer as still as possible during the measurement and always wait until the measured value has settled.

  2. Determine an average value from the measured values. If your pyrometer has the option of changing the emissivity, adjust it until the pyrometer shows you the same value when you measure the forehead temperature again as the measurement previously taken with the clinical thermometer.

  3. If an alarm limit can be set in the device and, for example, 38°C is assumed as the reaction limit for an increased core body temperature, set the limit accordingly to "38°C".

Programmable alarm thresholds make screening automated

With pyrometers like the BP17, reference temperatures and tolerance limits of 1°C, 3°C or 5°C can be set. If the temperature determined in advance during the self-measurement is set as the reaction limit and the measured temperature value lies outside the limit corridor, this is also shown in colour on the display and acoustically by means of a signal tone.

All the advantages of pyrometer measuring at a glance:

  • Contact-free fever screening
  • Excellent value for money
  • Acoustic and visual alarm when a preselectable temperature differential is not met/is exceeded (depending on model)

Notice: The pyrometer measurement can only be seen as an indicative screening and does not replace suitable temperature measurements with specially designed medical measuring devices.

We will be happy to advise you on your fever screening options

Always at your side when it comes to answering questions about measurement technology: Trotec Customer Service. The experts on the subject of temperature measurement in all areas are happy to help you on +49 2452 962-400 or by e-mail:

We look forward to helping you further.

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