How to get the best out of your infrared forehead thermometer

As businesses weather the COVID-19 pandemic, it has become government mandated to monitor the temperature of all employees. TMSA are proud to stock two brands of infrared forehead thermometers which, as we explain in our previous blog post, we consider to be strong options for all businesses. Here we discuss how to understand and best utilise your device, once purchased.

What is Infrared radiation?

Infrared is just one type of radiation within the electromagnetic spectrum.  Other types of electromagnetic radiation include microwaves, x-rays, and visible light. It is the infrared radiation in sunlight that causes sunburn, though hopefully the benefit of this cooler weather is less chance of that!  Infrared radiation is heat, and although we can’t see infrared radiation, we can feel it. Everyday examples might include the warmth we feel when holding a steaming hot cup of soup, or standing in the sun on a cold winter’s morning, or sitting in front of a roaring log fire.

How do IR thermometers measure temperature?

Simply put, the higher the temperature (heat emitted by) the surface of an object (in this case, the skin of the human forehead) the more electricity will be sent to the sensor (found inside the infrared thermometer) and the higher the reading shown on the screen of the thermometer.  It must be noted that infrared thermometers only read surface temperature. They are not capable of reading the core body temperature of a person, which in some cases can be up to 2 degrees Celcius higher than the external skin temperature on the forehead.

What factors could influence the reading accuracy?

  • The distance between the thermometer and the object. Please follow the manufacturer’s instructions in the operating manual enclosed with your device or contact us for guidance.
  • The angle of the lens. This must be perpendicular to the forehead and the person must remain still whilst the measurement is taken.
  • Ambient conditions also play a role in the reading, so it is best to take temperatures in the following environments in a draft-free area, with no direct sunlight, nor any nearby sources of radiant heat (e.g. heaters), where the temperature is16-40 degrees C, and relative humidity is below 85% percent. It is best to place the thermometer in the testing environment for 10-30 minutes prior to use in order for it to adapt to the ambient temperature.
  • A dirty or scratched lens can also affect the readings and it is recommended to clean the lens regularly following the manufacturer’s instructions.
  • The person whose temperature is being taken should also be appropriately prepared.
    • His/her forehead should be clean (including free of cosmetic creams), dry and not obscured by headgear or hair or lotions.
    • That he/she should not have had a hot drink or hot food immediately prior to temperature being taken.
    • That he/ she should not have been in a warmer or colder environment immediately prior to measurement being taken (e.g. sitting in a hot car, standing in the sun in a queue, wearing excessive clothing). We therefore advise thinking carefully about where your testing station is located, including the queue of people waiting for their temperatures to be taken.

Steps to be taken if a “Lo” or extremely high reading is obtained:

  • The employer or company concerned should have a protocol for such events. The person taking the readings should know what this protocol is, how to implement it, and who he/she should refer to if in doubt. It is important that the staff member/customer concerned is not victimised, and equally that he/she does not intimidate the person taking the reading into allowing him/her to proceed despite the unsatisfactory reading. The protocol could include steps such as:
  •  Asking the staff member/customer to wait for 5-10 minutes in a designated area away from other staff, to allow them to acclimatise (e.g. if they have come from a hotter or colder environment) before taking their temperature again.
  • If high temperature readings are obtained after at least three consecutive measurements 5-10 minutes apart the person should be referred to a medical doctor for further diagnosis.
  • Consideration could be given to testing on other exposed skin surfaces e.g. the neck (below the ear), the throat or on the wrist.
  • Given the number of factors that could result in a potentially inaccurate reading by an infrared thermometer, it is important that the person conducting the testing is aware of other observable Covid-19 symptoms e.g. coughing, redness of eyes, shortness of breath, or difficulty breathing. A combination of symptoms would be a better indicator of possible infection than the reading given by an infrared thermometer alone and could inform which further steps needed to be taken.

As businesses continue to adapt to operating amidst this pandemic, we remain contactable for advice or solutions to any temperature monitoring problems. Please don’t hesitate to contact us.


  1. How to measure your body temperature correctly using an infrared
  2. Quick Tips technical resources Healthcare and Laboratory.
  3. F02 Medical Infrared Body Thermometer (MIBT) Considerations and Precautions.