Handheld Infrared Thermometers

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What is a handheld infrared thermometer?

Thermometers have been available for hundreds of year and are reliable devices. Unfortunately, most of them need to stay on a specific place at least 10 minutes to accurately measure temperature. Most do not have probes or any other possibility to measure temperature in a specific part of a room or on an appliance.

Handheld infrared thermometers have are highly useful. Battery powered, compact and with good enough accuracy, can be held in one hand and pointed to any area no matter how large or small, from a distance or close-by. The measured value is shown on a small display continuously or only when triggered, being extremely easy to use.

The greatest advantage of such a device is that it can show, in a couple of seconds, issues in uniform cooling or heating on certain devices, thermal losses, with no training and in a straightforward matter. The measured area is highlighted by a laser pointer on some devices, making identification very easily.


There are varied infrared thermometers. Some offer basic functionality while others include additional costly features such as live thermal imaging. The most simple ones are affordable and useful enough if they have some minimal capabilities. While largely similar, medical devices are not preferred since they may be more accurate but lack an useful laser pointer to indicate the measured area.

While there are many brands and models, a good product should have the following capability:

  • wide measuring temperature range (-50 to 380 Celsius degrees or even more)
  • less than 1.5 Celsius degrees temperature deviation from reference
  • quickly display instant temperature reading in Celsius or Fahrenheit degrees
  • laser pointer with additional indication of measurement radius (center and edge red dots)
  • large dial display, illuminated LCD, durable case
  • use a single 9V battery or two AA batteries (simple maintenance)
  • continuous measurement temperature if trigger button is held
  • hold last reading after trigger button pressed and released (useful on hard to reach places)
  • show temperature variation from reference value with different screen colour

Infrared Thermometer

Despite the complexity of the above list requirements, most general purpose thermal scanners do have at least basic capabilities. Essential features are the laser pointer with radius indication and continuous measurement, to identify areas of concern.


The actual performance of a building envelope and the resulting comfort of its occupants depend on a relatively stable, continuous temperature in most areas. Finding places that influence airflow, such as cold or hot spots, can point at where remediation procedures must be concentrated. Space heating and cooling imbalances can be easily spot, potentially saving more energy.

On appliances, large temperature differences may be normal such as on large cooking, refrigeration or conditioning equipment. However, all large temperature differences may create poor device performance, affect nearby furniture or have other undesirable effects that have to be considered. Ideal locations can be found by comparing temperature measurements.

Note that both the initial state of the device, normal and full load conditions can be easily determined and compared with previous days and various mitigations, ensuring effective solutions can be found in time. The focus is on reducing large temperature swings with subsequent measures.

Typical testing scenario

Various temperature readings are made on a room, to determine where heat losses or heat gains manifest. Improper or no sealing on doors and windows can be found. For devices that get hot during use, high temperature concentrated in a specific place points at poor airflow and need to rearrange nearby furniture.

Location Ambient or exterior air temperature Highest temperature Lowest temperature Comments
12000 BTU Air conditioning unit (on cooling) 35 Celsius degrees exterior 20 Celsius degrees 15 Celsius degrees Outlet air temperature around 15 degrees when operating, otherwise cleaning or servicing required
12000 BTU Air conditioning unit (on heating) -5 Celsius degrees exterior 48 Celsius degrees 35 Celsius degrees Outlet air temperature around 35 degrees when operating, otherwise cleaning or servicing required
Typical water space heater on central heating systems -5 Celsius degrees exterior 50 Celsius degrees 38 Celsius degrees Large temperature on heater surface promote intense air currents, increase heat losses to exterior walls
300l Refrigerator (Freezer set at -18 Degrees Celsius) 19 to 33 Celsius degrees ambient 50 Celsius degrees 35 Celsius degrees Appliance backside temperature should not exceed 50 degrees in certain spots on adequate placement
Kitchen 19 to 33 Celsius degrees ambient 33 Celsius degrees 19 Celsius degrees Temperature near cooking devices not more than 30 degrees over ambient to avoid discomfort
Typical room 19 to 33 Celsius degrees ambient 31 Celsius degrees 19 Celsius degrees Temperature differences between various parts of the room less than 5 Celsius degrees to minimize drafts and losses
Windows -5 to 35 Celsius degrees ambient 40 Celsius degrees 15 Celsius degrees Glass surface temperature less than 5 degrees over/under window frame on energy efficient modern windows, in intense sun or blizzard conditions
Partition doors 10 to 33 Celsius degrees ambient 30 Celsius degrees 19 Celsius degrees Surface temperature less than 3 degrees over/under nearby wall temperature for well sealed doors, regardless of air circulation and temperature on each side
Interior facade walls (in summer) 35 Celsius degrees exterior 32 Celsius degrees 28 Celsius degrees If interior side temperature exceeds 30-32 degrees in sunny days, more external insulation/shading is required
Interior facade walls (in winter) -5 Celsius degrees exterior 20 Celsius degrees 15 Celsius degrees If interior side temperature drops below 15 degrees in very cold days, more external insulation is required to avoid mold growth

Hot or cold spot temperatures may be relative. Note that first readings may be different from ones made after two or three minutes, as some affordable infrared thermometers may not have proper recalibration.

Food processing and storage can also benefit from sample temperature measurements to ensure conformity or other requirements, adjustments for lower energy consumption or another desired result.

Monitoring suggestions

Readings can be made at any time. Ensuring that some are done in worst conditions such as high occupancy, intense activity, very cold winter day, very hot summer day, high humidity, intense sun, some doors and windows closed or opened, creates enough scenarios to test various improvements.

Infrared Thermometer Laser Pointer Shows Measurement Radius

Measurement at a distance of around 3m, with this sample unit, is averaged inside a 20 centimeters diameter circle.

Keep in mind that the further you are from the surface you point the thermometer at, the wider the measurement area so if accurate evaluations are required, the device should be placed as close as possible to the area of interest. To understand what is actually measured, the scan radius laser pointer cast from the thermometer is very important.


Monitoring temperature anytime and anywhere, particularly in hard to reach locations, as close as a few centimeters or as far as a few meters, even if measurement accuracy may not be ideal, is extremely important.

Note that also particular food processing or other small manufacturing processes can be monitored on sample products with this device so its usefulness extends greatly beyond typical scenarios.