Infrared thermometers are non-contact devices used to measure surface temperature, commonly seen in homes and public spaces. Their increased visibility has led to questions about the safety of their underlying technology. The primary concern is whether these devices emit radiation that could harm the person being measured. Understanding how these devices function provides a clear answer to these safety queries.
How Infrared Thermometers Measure Temperature
Infrared thermometers are passive devices, operating as receivers rather than transmitters. Any object with a temperature above absolute zero naturally emits thermal radiation within the infrared (IR) spectrum. The device’s lens collects this naturally emitted infrared energy from the target, such as a person’s forehead.
The collected energy is focused onto a specialized sensor known as a thermopile. This sensor converts the thermal energy into an electrical signal. Internal electronics process this signal, applying a temperature calculation to display the reading. The thermometer is simply sensing the heat already radiating from the body.
Physical Safety Concerns of Infrared Emission
The infrared radiation detected by these thermometers is harmless because the device does not send energy toward the person. This passive detection eliminates the risk of transmitting energy or radiation into the body or eyes. The electromagnetic energy measured is non-ionizing, meaning it lacks the energy to break chemical bonds or damage cellular DNA, unlike X-rays or gamma rays.
Many non-contact infrared thermometers (NCITs) intended for medical use do not feature an aiming laser. If a model includes a visible aiming laser, it is a separate component used only to indicate the measurement spot. This laser is not part of the temperature-sensing mechanism. These lasers are low-power, often rated as Class 1 or Class 2 products, which are safe for brief, accidental exposure. Users should still avoid staring directly into the beam.
These devices are regulated by the U.S. Food and Drug Administration (FDA) as Class II medical devices. This regulation ensures they meet performance and safety standards. Because the measurement is non-contact and non-invasive, NCITs are safe for use on all populations, including infants and children. There is no physical danger associated with using the device near the eyes or on sensitive skin areas.
Ensuring Accuracy Through Proper Usage
While the device is physically safe, its utility in a medical context depends heavily on accuracy, which is influenced by operational factors. Non-contact thermometers measure the surface temperature of the skin, which can fluctuate due to environmental conditions. For the most reliable reading, the device should be aimed perpendicular to the center of the forehead or the temporal artery area.
Environmental conditions can compromise the reading, so measurements should be taken in a draft-free space away from direct sunlight or radiant heat sources. If the thermometer has been stored in a hot or cold area, it must acclimate to room temperature for 10 to 30 minutes before use. Moisture, such as sweat on the forehead, can cause a falsely low reading, so the area should be dry.
The sensor lens must be kept clean and free of dust or fingerprints, as obstruction blocks incoming infrared energy and alters the result. The distance between the thermometer and the person’s forehead is specific to each model. Users must strictly follow the manufacturer’s distance guidelines. Following these procedures ensures the thermometer provides a reliable indicator of potential fever.