Methods of temperature measurement

Clinical mercury thermometers
Traditional mercury thermometers have been used for many years in clinical settings and may be used in the mouth, the axilla or the rectum. Although they are familiar to nurses and clients, their use has declined in recent years due to the potential hazards of mercury spillage and broken glass. There is also controversy surrounding accuracy of measurement and the length of time a mercury thermometer needs to be left in place. Types available include oral, rectal and subnormal (those that record
below 35ºC), and disposable covers are readily available to reduce the risk of cross-infection.

Electronic thermometers
These have become more popular in recent years and are often purchased for use in the home. An internal probe is connected to a power supply that has a display unit and bleeps when the maximum temperature is reached. They can be used in the mouth, the axilla or the rectum and should be covered with a clean disposable probe cover for each patient. They take significantly less time to register an accurate temperature than traditional thermometers and have therefore become increasingly popular. Though incurring a more significant cost they are considered a much safer product.

Tympanic thermometers
These are placed in the ear canal and heat is detected as infra-red energy from the tympanic membrane. It is a rapid way of measuring temperature, only taking a few seconds, but there is some controversy over the accuracy of measurement. They are probably the most widely used devices used in hospitals today.

Chemical disposable thermometers
These may be used in the mouth or the axilla. They are usually plastic strips which are impregnated with thermo-sensitive chemicals that change colour with increasing temperature. As these are disposable there is no risk of cross-infection.

Disposable strips
These are widely available from retail pharmacies and consist of individually wrapped strips for single use only. The strip is applied to the forehead until a reading can be visualized on the strip. Whilst they can give a broad indication of whether the individual is hot or cold they are the least accurate and only really serve as a very basic guide as to whether more professional attention is needed.