How to measure body temperature correctly using an infrared thermometer

By Testo South Africa SANAS Calibration Lab JHB on 21 April 2020

In recent weeks, many companies have introduced additional screening methods for employees in order to comply with their legal obligation in Section 8 of the Occupational Health and Safety Act, 1993 (OHSA). This requires every employer to provide and maintain, as far as reasonably practicable, a working environment that is safe and without risks to the health of its employees.

This duty includes (i) taking steps to eliminate or mitigate any hazard or potential hazard, before resorting to personal protective equipment; (ii) providing information, instructions, training and supervision that may be necessary to ensure the health and safety of employees at work; and (iii) enforcing such measures as may be necessary for the interests of health and safety. Section 9 extends these duties towards persons other than those in employment affected by the employer’s activities such as visitors and contractors.

In order to ensure employees are safe, the law permits employers to impose rules on their employees in order to ensure a safe working environment and, in addition, it may place conditions on entry into its premises.  In light of COVID-19, many employers have reviewed their rules and a legitimate entry requirement may now be requiring the disclosure of recent international travel and subjecting individuals to a temperature test. Monitoring the health status of an employee is not a new requirement for the food industry as daily fitness checks are part of an effective PRP programme for personal hygiene.

However, taking someone’s temperature is not our normal practice and as such there are a few considerations:

  • Any such test must be conducted with due regard to the individual’s privacy.
  • Educate employees on the reason for this requirement
  • Ensure you have their documented consent first
  • The temperature test itself should be as un-invasive as possible. An infrared thermometer/ pyrometer such as the testo 830 can be used for temperature scanning rather than one that is inserted into the ear/ mouth or under arm. This kind of thermometer reads thermal radiation; it measures the object’s surface temperature rather than the internal temperature. It does not penetrate the surface, but rather gathers information by sensing the heat coming off of the object itself. It is, therefore, a safer way to scan temperature because the thermometer will not be contaminated. It should be noted however that the testo 830 infrared temperature measuring device is not classified as a medical thermometer. It uses the same technology, but the information it provides needs to be interpreted by the user.

 As measuring someone’s temperature is normally part of a medical examination undertaken by a qualified medical practitioner, you should take careful note of the following:

  • A good guideline to note is that your (internal) body temperature is normally about 2° C higher than the external (skin) temperature on your forehead (i.e. 36.1° C on your forehead would translate to approximately 38.1° C body temperature – a possible indication of fever)” Refer to figure 1 for more information

Fig 1.

  • There should be an adaptation period, based on where the person comes from (i.e. the cold/ warm outdoors), before the temperature is scanned. This would also apply when you take the IR thermometer from inside, too (a warmer/ colder) environment.
  • The site of temperature scanning is also important. Most commonly used is the forehead.
  • The recommended best practice is to measure a sample of 5 people at room temperature (on their forehead) and measure the same people outside (at the warmer/ colder temperature) to get a more accurate indication.
  • There can be variation in basal body temperature depending on gender, age, time of day, exertion level, health status (such as illness and menstruation), what part of the body the measurement is taken at, state of consciousness (waking, sleeping, sedated), and emotions.
  • Infrared thermometers are extremely accurate when being used correctly. Not all materials give off thermal radiation in the same way, and a material’s ability to give off this type of energy is known as its emissivity. Emissivity is measured on a scale from 0.00 – 1.00. The emissivity of your IR thermometer should be set to 0.98 for measuring skin. It is only possible to change the emissivity with some IR thermometers (like the testo 830). For some IR thermometers, the emissivity is fixed, so you have to make sure that it is compatible with human temperature scanning BEFORE you start using it.
  • The distance you measure a subject from also affects the result. The general rule of thumb is the closer, the better (approximately 5cm from the thermometer to the forehead). However different IR thermometers offer different accuracies (for example the testo 830-T2 measures more accurate at a greater distance than the testo 830-T1)
  • The measuring accuracy of your thermometer is also a factor to consider – please check your technical specifications for this information.
  • The infrared thermometers give you a good indication of whether someone is running a fever, which should then be investigated further by a medical practitioner.



Fig 1:

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