Fever Screening Explained

Spectral range: 7 – 13 µm

Optical resolution (IR): 640 x 480 pixels

Frame rate: Up to 32 Hz

Thermal sensitivity : 75 mK

Temperature measurement sensitivity (comparative ?) : 0.01°C.

Temperature range in medical specification 17°C to 38°C (scalable via software): -20°C – 250°C.

Auto Ambient correction.

Optics: 33° x 25°, 19 mm or 15° x 11°, 41.5 mm or 60° x 45°, 10 mm.

Accuracy: (absolute temperature) ±2°C or ±2%. Accuracy: (comparative ?) 0.01°C

PC interface: USB 2.0 or 3.0

Ambient temperature : 0°C to 50°C

Storage temperature: -40°C to 70°C

Relative humidity: 20 – 80%, non condensing

Enclosure size : 55 mm x 150 mm x 250 mm

Weight: 1020 g (2lb 4oz)

Shock / vibration: 25G, IEC 68-2-29 / 2G, IEC 68-2-6

Power supply: USB powered. PC, Laptop or Tablet running Windows.

WinTES3 camera control and analysis software.

Optional rechargeable power supply (back-up power for laptop or tablet)

The system should be set-up as close to passenger’s entry into terminal as possible. An area of minimal reflected infrared should be chosen. Infrared sources including all incandescent, halogen, or any other heat producing lighting should be avoided, infrared producing lighting should be replaced with florescent / LED lights.

The ideal temperature for the scanning area is 21°C. (Good results are achieved with any ambient temperatures between 19°C and 27°C but reliable data can be achieved in temperatures up to 35°C if temperature range of detection is reduced from 8 °C to 5 °C)

Air conditioning should not blow cold air onto the subjects being scanned, (if cold air can be felt on the face, air conditioning ducts should be moved or baffled to diffuse or divert the air from the persons being scanned. A plain, non reflective background (wall or partition) should be behind the subjects for best results.

The focal length from subjects to scanner should be between 2.5 m and 5 m. Optimum distance is 3 m. for low to mid definition cameras (160×120 to 380×280). High definition cameras 640×480 > allow for wider FOV at greater distances while maintaining accuracy and sensitivity from 2m up to 20m

Scanner should be mounted above passenger head level and angled slightly down in order to bring a sufficient number of passengers into the field of view. (average of 10 passengers within the screen view or per scan is recommended).

Children can be carried or stand with parents.

Wheelchair passengers and females with total head covering should proceed straight to manual temperature measuring station.

Make sure that all cables and connections are properly connected to computer and scanner and that power is on.

Start the WinTes software and start default scanning (used for general passenger scanning) ‘Note’ It is easier to set focus using full screen and then change to threshold detection window to scan passengers.

 It is good protocol to set up system at least ten minutes before a flight disembarks and passengers present for screening. The scanner will stabilize within approximately 30 seconds, but it is good protocol to run scanner for a few minutes before screening passengers.

If the threshold alarm is used : set the threshold to 1 deg C above normal (evaluated by screening test subjects at the location being controlled) and test threshold alarm with a known target temperature source (cup of fluid with thermometer at 39 deg C will suffice)

If a full color window is used : Set the colour scale to a threshold using the beginning of the red… (Bring the colours up or down until the image shows just the first pixels or pixel of red) this will show colour changes that can be assessed visibly at a glance without applying a statistical analysis.

There can be a wide range of normal temperature between passengers, dependant on sex, metabolism and many other factors but average skin temperatures will range between 35 °C and 37.5 °C.

 Use the colour scale (set colours) exclusively, rather than setting the minimum and maximum temperature range. 

Make sure that :

– ‘RANGE’ is set to 8 °C.

– Threshold alarm is set at or below 39 deg C

Passengers undergoing secondary scanning should be advised to remove eye glasses and masks if any. 

The minimum required area of the face that must be uncovered is from above the eyebrows to below the nose.

For secondary screening the passengers should look straight ahead (or at the camera) and stop briefly in a designated area.

Passengers should be pre advised that the scan is non radiation and has no risk. (this is best done at the time passengers are given an INFECTION risk questionnaire before scanning or can be posted on a notice board at the FEVER screening station).

Passengers should be controlled / organized as they approach the scanning area so they pass at a reasonable speed.

For any secondary screening it is beneficial for passengers to observe other passengers being scanned in order to know what to do…… better compliance).

For secondary screening a square area should be marked out on the floor which passengers can stand in to be scanned. This positions the individual or group of passengers correctly. (coloured tape can be used but the best method is to use crowd barriers or portable gates).

 A line on the floor for passengers to wait at should be made on the approach to the scanning area so passengers are close too, and ready to step into the square for scanning, saving time.

The passengers being scanned as a secondary test are told to remove any eye glasses or surgical masks and look straight ahead for the couple of seconds while they are being scanned.

As soon as the scan has completed, this group of passengers can be dismissed (provided the scan is within normal limits) and the next group of passengers directed to stand in the scanning area.

Interpretation of secondary scan results:

(This applies to the majority of individuals who tested just above the threshold alarm)

The majority of each passengers face will be in the green range with some percentage of yellow and orange, there is normally increased temperature around the medial eyes which may show as red or even white but this is localized and does not affect the average temperature significantly.

The region of the face used for statistical analysis is from below the hairline and above the eyebrow to below the nose and above the mouth.

When setting a secondary threshold it is important to keep the statistics box within the boarder of the face so only body temperature is included and not the temperature of the background behind the passenger.

If a region of interest statistical analysis is performed the average temperatures should be between 35°C and 38°C. The maximum temperature seen in the statistics does not signify core temperature.

Statistical analysis with an average temperature of over 38 °C should be considered suspicious and that passenger should have a tympanic temperature measurement conducted.

Pattern recognition is important, increased patterns of red or white throughout the face is suspicious. A ‘mottled’ appearance of the reds and whites throughout the face, particularly around the nose and forehead are suspicious and justifies performing statistical analysis and or proceeding to tympanic temperature measurement.

Hypothermia can be just as suspicious as hyperthermia. A passenger who is perspiring will present as significantly cooler, normally in the blue range of colour. (this is due to evaporative cooling effect). These passengers should also progress to tympanic temperature measurement.

There are minimal false positives as a febril subject will present with an obviously different thermal signature than the majority of comparable fellow passengers.

Passengers with local pathology affecting the face generally do not produce a suspicious result as do subjects with systemic pathology.

Some local pathologies can include dental or periodontal infection, sinusitis and headache. Systemic pathologies can include autonomic dysfunction, hormonal changes, thyroid dysfunction and all other systemic diseases. (pregnancy will also cause increased core temperature of one degree).

If in doubt, perform a tympanic temperature measurement to correlate with thermal findings.

A digital thermometer to measure ambient temperature.

Gloves and masks as per WHO / CDC guidelines. (any passenger testing positive should immediately be asked to wear an approved (N95) mask.

A hazardous materials bin should be available for disposal of tympanic thermometer covers and any other material considered potentially infectious.

A tape measure for measuring focal distances (fine tuning is done by using images as guide).

Courtesy at all times.

The process of screening should not cause concern or distress. (answer passengers’ questions)