With the current health atmosphere during the coronavirus pandemic, it is increasingly necessary for employers and public service businesses to screen employees, customers and vendors that enter their facilities to detect those that may have a fever and an elevated body temperature. Public areas such as schools, hospitals, hotels, airports and other places where large public gatherings could occur need to quickly identify someone who might be showing symptoms of the
Measuring an individual’s body temperature is typically performed in two ways, through contact thermometers that are placed on the forehead or in the mouth, ear, or armpit, or through non-contact thermometers that allow a person’s temperature to be taken without contacting the individual. The contact method does not allow for easy, quick or sanitary measurements when large numbers of individuals need to be tested, so the non-contact method has become increasingly popular for taking body temperature measurements.
Infrared (IR) Thermometers
The most common type of equipment used for taking non-contact measurements are Infrared (IR) Thermometers. IR Thermometers work by detecting the infrared radiation that all objects give off as heat. They are used in many industrial settings for a wide range of temperature measuring applications. They are lightweight, easy to use and can take temperature measurements in only a few seconds, which is important when screening large numbers of people.
One of the biggest questions in using IR Thermometers is whether you can take accurate body temperature measurements with them. There are two main types of IR Thermometers, general/industrial IR Thermometers and medical or clinical IR Thermometers approved by the FDA.
Industrial IR Thermometers are typically used for food service and processing, scientific and industrial applications and general home use. They are not designed for medical use and have a number of characteristics that make them inaccurate for body temperature measurements.
IR Thermometers are only designed to indicate the temperature at the surface of the object being measured. When measuring the skin of the forehead, the reading will be several degrees lower than the internal body temperature, even if a fever is present.
Industrial IR Thermometers are designed to measure a wide range of temperatures, from as low as -50°F to over 900°F. Their specifications are set up to encompass this entire range so they are not highly accurate in any specific temperature range. In the area of 100°F, even the best industrial IR Thermometers have accuracies of around 2°F (1°C) and most of them have accuracies of 3°F to 4°F.
All IR Thermometers have an ‘Emissivity’ setting that is set to indicate the ‘reflectivity’ of an object. Darker objects require an emissivity setting from between 0.90 to 1.00 and bright, shiny objects may require an emissivity setting of between 0.20 to 0.50, depending on the material. The emissivity of human skin is usually between 0.97 and 0.98. Some IR Thermometers have adjustable emissivity’s, however, most of the more popular, less expensive IR Thermometers have a fixed emissivity of 0.95. When used for body temperature measurements, this difference in emissivity setting can cause an additional error of 1°F to 2°F.
When all of the potential errors are added together, an error of over 5°F could be present when using an ordinary industrial IR Thermometer to measure body temperatures, which makes them inadequate for accurate body temperature use.
Medical IR Thermometers that are approved by the FDA have several advantages over industrial IR Thermometers that make them significantly more accurate in performing external body temperature measurements.
First, medical IR Thermometers are designed to have their best response in the temperature range between approximately 90 to 110°F. Since they are measuring in such a narrow range, their accuracies can be optimized to be the most accurate for those specific measurements. Accuracies of 0.5°F or better can be achieved with medical IR Thermometers.
Medical IR Thermometers are also programmed to make mathematical adjustments to the surface temperature readings to display an equivalent oral temperature. This can give a true internal body temperature reading.
Medical IR Thermometers also have the fixed emissivity set to 0.97 or 0.98 to more accurately measure the emissivity of human skin, so no additional emissivity errors are encountered in the measurement.
For accurate body temperature measurements, medical IR Thermometers should only be used.
Proper Use of IR Thermometers
In using any IR Thermometer for body temperature measurements, there are specific procedures to be followed to achieve the most accurate measurements. The manufacturer’s operating manual should be referenced for the specific guidelines and instructions to use the specific IR Thermometer.
The environment the IR Thermometer is used in is important to its performance. It should be used in an area free of drafts, out of direct sunlight and where there is no smoke, dust, or other particles in the air. The IR Thermometer should be allowed to adjust to the environment for 10-30 minutes prior to use.
Many IR Thermometers have a laser-pointing feature that is used to assist in aiming the thermometer. When using the thermometer for body temperature measurements, the laser should be turned off or covered with tape to avoid pointing the laser at someone’s eyes. When taking the measurement, the IR Thermometer should be held completely perpendicular to the forehead.
IR Thermometers measurement area or ‘spot size’ is a function of the distance from the thermometer to the target. IR Thermometers must be used at a specific distance to obtain an accurate reading. The manufacturer’s manual will indicate the correct measurement distances to obtain the most accurate measurement.
No matter which type of non-contact device is used for body temperature measurements, they should only be used in a screening function and should not be regarded as an absolute measurement of body temperature. Internal body temperature measurements should always be made when decisions about quarantine or isolation are to be made to prevent false readings and the quarantining of people who aren’t sick.
For more information on the proper use of IR Thermometers, contact e2b calibration.
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