Measuring tympanic temperature (see Procedure guideline 14.6: Tympanic temperature measurement) requires a tympanic membrane thermometer. This is a small hand‐held device that has a disposable probe cover that is inserted into the patient's ear canal. The sensor at the end of the probe records the infra‐red radiation that is emitted by the tympanic membrane, as a result of its warmth, and converts this into a temperature reading presented on a digital screen (El‐Radhi [59]). The probe is protected by a disposable cover, which is changed between patients to prevent cross‐infection (Grainger [75]). Advantages of tympanic membrane thermometry are speed (temperature reading available within seconds), safety and ease of use (Gasim et al. [69]).

A common problem with using tympanic thermometers is poor technique leading to inaccurate temperature measurements (Bijur et al. [19], Jevon and Ewens [88]). The placement of the probe to fit snugly within the ear canal (Figure 14.38) is crucial as the difference in temperature between the opening of the ear canal and the tympanic membrane can be as high as 2°C (Lewis [103]). Other causes of false readings include a dirty or cracked probe lens and incorrect installation of the probe cover (WelchAllyn [208]). Ear infections and wax are reported to influence the true temperature of the tympanum (Basak et al. [14]); therefore, the ear should be inspected prior to obtaining a reading, and, if wax or evidence of an infection is present, an alternative route for obtaining the temperature should be sought (Grainger [75]). For infection prevention and control purposes, the appropriate disposable probe cover should be used and the healthcare professional should inspect the cover to ensure that it has been fitted correctly and that there are no wrinkles over the tip end. This will ensure an accurate reading is achieved (Grainger [75]).