Disposable thermometers are single-use temperature measurement devices, typically appearing as flexible strips or small dot matrix cards. These devices contain heat-sensitive materials that change color when exposed to body temperature. Their primary benefit is the prevention of cross-contamination, making them a preferred choice in healthcare settings and homes for infection control.
Preparation and Placement
Before taking a measurement, check the product’s expiration date to ensure the temperature-sensitive chemicals are reliable. For an oral reading, the individual must not have consumed hot or cold liquids, chewed gum, or smoked within the last 15 minutes. These activities can temporarily alter the surface temperature of the mouth, leading to an inaccurate result.
To take an oral temperature, place the sensitive tip deep under the tongue. The thermometer must rest in one of the heat pockets located on either side of the base of the tongue. Instruct the person to press their tongue down and keep their mouth closed for the duration of the measurement. For an axillary (underarm) reading, the area must be clean and completely dry before placing the device. The dot matrix side should be placed directly against the torso, parallel to the body’s length, and held firmly in place by the arm for the designated time.
Reading and Interpreting the Result
Reading involves observing the color change on the dot matrix after the required duration. For an oral reading, the thermometer typically remains in place for 60 seconds, while an axillary reading requires three minutes. After removing the strip, wait approximately 10 seconds for the chemical dots to stabilize and “lock in” the final temperature.
The reading is determined by identifying the highest point on the scale where a dot has permanently changed color, usually to blue. If there are uncolored dots between the last colored dot and the one before it, these “skipped dots” should be ignored. The reading corresponds to the last fully activated color change. A normal oral temperature is generally considered to be around 98.6°F (37.0°C). A temperature reading of 100.4°F (38.0°C) or higher, depending on the measurement site, is typically considered a fever.
Understanding Accuracy and Limitations
Disposable thermometers are accurate to within ±0.2°F in the clinically relevant temperature range. However, they have a slightly wider margin of error than high-precision digital instruments. The sensitivity of the chemical indicators means that external factors can more easily compromise the final reading.
Poor placement, such as not reaching the sublingual heat pocket, or ambient room temperature affecting an axillary reading, can impact the result. An axillary temperature is often naturally lower than an oral reading. If a reading is unexpectedly high or low, or if a definitive diagnosis is needed, a second measurement with a high-precision device may be necessary for confirmation.
Proper Handling and Disposal
For optimal performance, unused disposable thermometers should be stored in a cool, dry place and shielded from exposure to extreme heat or direct sunlight. Exposure can prematurely activate the temperature-sensitive dots. The maximum storage temperature is generally around 86°F or 30°C.
After a temperature has been taken and recorded, the thermometer must be discarded immediately. Since these devices are non-electronic and mercury-free, they are typically disposed of in the regular waste stream as single-use medical material. Immediate disposal prevents the transmission of infectious agents.