The Pitt Prescription | Exploring different types of thermometers and the role of fevers in COVID-19

Walking into almost any establishment — restaurants, University buildings, hospitals — it is common to be greeted at the door by some sort of temperature-monitoring station.

As fevers are one of the common symptoms of COVID-19, it makes sense that businesses would want to make sure nobody is entering with a high temperature. From forehead thermometers to temperature kiosks, we see many different tools being used to measure bodily temperature. 

Types of thermometers

There are several different types of thermometers, such as digital, tympanic and temporal. Additionally, thermal infrared temperature kiosks can be used to measure a person’s body temperature, and these are seen in many establishments during the ongoing pandemic. Each type of thermometer has its own temperature limit that indicates the presence of a fever. The limits listed in this article come from the APhA Handbook of Nonprescription Drugs Quick Reference.

Digital thermometers are some of the most commonly seen thermometers because of their easy use and their availability in many drug stores. Digital thermometers are often seen as the quickest and most accurate way to measure body temperature, especially in children. The three main areas where a digital thermometer can be used are the mouth, the rectum and the armpit (although this location does not give the most accurate reading).

Oral (mouth) digital thermometers: These are used underneath the tongue and are best for adults and children over the age of 4 years. To properly use an oral thermometer, insert the tip underneath the tongue and hold for 30 to 60 seconds, or until the thermometer beeps to indicate it has a reading. For oral digital thermometers, a temperature at or above 99.5 degrees Fahrenheit is considered a fever.

Rectal digital thermometers: These thermometers are the most invasive of the digital thermometers, but they also provide the most accurate body temperature reading. The tip of the thermometer should be gently inserted into the rectum and held there for 30 to 60 seconds. This technique is best for babies under 3 months old but is also commonly used in children under 3 years. For rectal thermometers, a temperature at or above 100.4 degrees is considered a fever.

Axillary (armpit) digital thermometers: These are inserted underneath the armpit and should be held in place for 30 to 60 seconds to obtain a reading. However, the armpit is the least accurate area to measure temperature with a digital thermometer. For axillary thermometers, a temperature at or above 99.3 degrees is considered a fever.

Tympanic (ear) thermometers are commonly used in infants and children over the age of 3 months. These thermometers are simple to use and require inserting the tip into the ear cavity to get an infrared reading. For babies less than a year old, their ear should be pulled back and then the tip should get inserted. For children more than a year old, their ear must be pulled back and up before inserting the tip.

However, there are some drawbacks to this type of thermometer. If the child has a buildup of earwax, then the reading will be less accurate. Additionally, the weather can affect the reading — for instance, if a child plays outside in the winter and then gets their temperature checked once they come inside, it would report an artificially low temperature. For tympanic thermometers, a temperature at or above 100 degrees is considered a fever.

Forehead thermometers come in two styles — temporal, which requires skin contact, and infrared, which is contactless and what many businesses are using for their COVID-19 screenings. It is important to note that like tympanic thermometers, their readings can be impacted by environmental factors, so they should be located inside away from any harsh temperatures or air movement.

Temporal forehead thermometers: These thermometers are used to measure the temperature of the temporal artery and need to make contact with the skin above the artery while being held in place for an accurate reading. These thermometers are typically more accurate than tympanic thermometers, but digital are still preferred. To get a temperature reading, the thermometer should be placed on a clean forehead out of direct sunlight and gently swiped across the skin.

Infrared forehead thermometers: More recently, contactless forehead thermometers have been making an appearance. They use infrared technology to measure the temperature of the skin — however, they may not be as accurate as digital or temporal thermometers.

The fever threshold for forehead thermometers differs with increasing age. For up to 2 months, a temperature at or above 100.7 degrees is considered a fever. For 3 months to four years old, a temperature at or above 100.3 degrees is considered a fever. For anyone 4 years or older, a temperature at or above 100.1 degrees is considered a fever.

Thermal temperature kiosks are becoming increasingly popular for temperature screenings during the COVID-19 pandemic. Many businesses, as well as Pitt, are using them upon entry into their buildings, such as Hillman Library and Salk Hall. These kiosks are equipped with cameras that can sense the subject’s temperature using infrared energy and provide a quick reading. Most kiosks enable the user to set the temperature cutoff, and there is not much evidence on what temperature range should be considered a fever — however, it is thought that it is similar to forehead thermometers’ range. The main benefit of these kiosks is that they are quick to use, mostly accurate and require no close contact between people.

Many people are questioning if these devices are even accurate, as they often give similar numbers to the majority of people using them. The Food and Drug Administration reports that when used properly, these imaging systems can provide accurate readings for one person at a time. They are not effective if trying to measure several people at once, but otherwise, they can be regarded as accurate.

How temperature readings relate to COVID-19
Something important to note is that although COVID-19 commonly presents with a fever, not every person who is infected may have that symptom. Not everybody with a fever has COVID-19, and not everybody with COVID-19 has a fever.

Fevers typically indicate some sort of illness, so preventing entry into businesses to those with high body temperatures is a smart safety measure, especially during a pandemic. It’s important to realize that there are also medications that can help lower fevers, which can cause an artificially low temperature reading. Ultimately, temperature monitoring is a beneficial aspect to maintaining safety during this pandemic — it’s not nearly enough to solely do that, though.

Temperature screenings can sometimes give a sense of security, but it should be noted that people with COVID-19 can still pass through if they are asymptomatic, have other symptoms excluding a fever or if they’ve been recently infected and haven’t started to present symptoms yet. Because of this, it is important for people to continue to wear masks and uphold safe social practices such as distancing and hand-washing even if you are in a temperature-monitored space.