An infrared forehead thermometer, often called a temporal artery thermometer, is a non-contact device that measures the thermal radiation naturally emitted by the skin over the temporal artery on the forehead. A sensor captures the infrared energy and converts it into a temperature reading within seconds. The ability to obtain a fast result without physical contact has made these thermometers popular, especially when checking children or multiple people.
Ensuring Accurate Readings
Achieving a reliable reading requires proper preparation of both the device and the environment, as infrared thermometers are sensitive to external factors. The thermometer must acclimate to the measurement room’s conditions, typically by placing it in the room for 10 to 30 minutes before use. This ensures the device’s internal components stabilize, preventing inaccuracies that occur if the thermometer is moved from a significantly colder or warmer space.
The measurement environment should be free of drafts, direct sunlight, or strong radiant heat sources like heaters or fireplaces. An optimal ambient temperature for use generally falls between 60.8°F and 104°F (16°C and 40°C), depending on the specific model. The forehead must also be clean and dry, free from sweat, cosmetics, or creams that can interfere with the infrared signal.
Avoid taking a reading immediately after the person has engaged in strenuous physical activity, bathing, or wearing a tight hat or head covering. These actions can alter the surface temperature of the skin, leading to a reading that does not accurately reflect the body’s internal temperature. Controlling these environmental and physical variables establishes the best possible conditions for an accurate measurement.
Step-by-Step Measurement Guide
Begin by ensuring the thermometer is set to the “body” or “human” mode, as many devices include a “surface” mode intended for objects. Hold the thermometer by the handle, keeping the sensor lens clean and untouched. Position the device perpendicular to the forehead, aimed at the center just above the eyebrows.
The distance from the skin varies by model, but it is typically a short range of 1 to 2 inches (3 to 5 centimeters) away from the forehead. Holding the thermometer too far away can result in a drop in accuracy or an error reading. Once positioned and aimed, press and quickly release the measurement button, often labeled “Scan” or “Measure.”
The device will capture the thermal emission, and the reading will be displayed on the screen, usually accompanied by an audible beep or a color-coded indicator. Hold the thermometer steady during the brief scan time, which is often less than a second. If multiple readings are needed, wait a few moments between each scan to allow the skin temperature to stabilize and the sensor to reset, ensuring consistent results.
Understanding the Results
The number displayed represents the surface temperature of the forehead, which the device’s internal algorithm translates into an estimated oral-equivalent temperature. For adults, a typical normal temperature range falls between 97°F and 99°F (36.1°C and 37.2°C). Forehead readings are often slightly lower than those taken orally, possibly by 0.5°F to 1.0°F (0.3°C to 0.6°C).
A temperature of 100.4°F (38°C) or higher is generally considered a fever in both adults and children. A person’s baseline temperature naturally varies throughout the day, often being lowest in the morning and highest in the late afternoon. For children, the normal range is slightly wider, typically between 95.9°F and 99.5°F.
Rather than relying on a single measurement, it is helpful to track a trend of temperatures over time to understand a person’s specific pattern. If a high reading is obtained, taking a second or third measurement a few minutes apart can help confirm the result and ensure it is not a momentary fluctuation. Interpreting the reading in context with other symptoms is always advisable.
Common Errors and Troubleshooting
Inconsistent or inaccurate readings often result from environmental interference or minor user errors. A frequent issue is debris on the sensor lens, which can block the infrared radiation. The lens should be gently wiped with a cotton swab dampened with alcohol to maintain clarity.
Drafts from open windows or air conditioning vents can rapidly cool the skin surface, resulting in a spuriously low reading. Similarly, sweat or hair obstructing the path to the temporal artery may skew the reading. If the device gives an error code or an unusually low reading, first check the battery, as a low charge can affect performance.
If a reading seems unusually high or low, wait about 15 minutes, move to a temperature-controlled area, and then re-measure to allow the body to stabilize. Maintaining the device involves storing it in its case in a cool, dry place and avoiding drops or physical damage that could affect the internal calibration.