Thermometers are an essential first-aid kit item, but their infrared, gun-shaped variant has become one of the most widely used for checking people in crowded places. Is it necessary to have one at home? Three experts give their verdict.
For months now, we've been getting "gunned down" by thermometers. Streets, roads, shopping centers, supermarkets, and airports are some of the places where you've probably been checked by a health official, guard, or inspector, aiming directly at your body.
At first, many people got nervous, especially when the gun-thermometer couldn't calculate their temperature and therefore aimed at another part, like the neck or wrist. Today, that "shot" is just another routine measure in this new "normal" scenario.
But just as our temperature is taken before entering almost any public place, should we do the same with those who visit us? Is it essential to have a thermometer at home? Three health experts respond.
Types of thermometers
The first thing to know is that there are different types of thermometers.
Mercury thermometer
This is the one most people have in their first-aid kit. "Its accuracy and precision are superior to others," says nurse Carolina Calderón from Clínica Alemana. Its weakness is that it can break easily, "and since mercury evaporates, it can be a risk to the body," says the professional.
This thermometer must be disinfected after each use, and the device's temperature must be manually reset. Another characteristic, not very convenient for everyone, is that "the reading result is not very visible," adds Calderón, and it can take between 4 to 5 minutes to become noticeable.
Ignacio Silva, an infectologist and academic at the Postgraduate Directorate of the Faculty of Medical Sciences at the University of Santiago, adds that, although they are "accurate," they are no longer "as recommendable due to the risk of poisoning."
Digital thermometer
This is a kind of upgrade from the traditional mercury thermometer, as its digital cousin works through "a metallic detector at the tip, which heats up on contact with the body's skin, giving us the reading after a few minutes on a digital screen," specifies Carolina Calderón.
Regarding its effectiveness, this model can occasionally fail, "potentially varying by up to two degrees from the real body temperature," explains the nurse. This small device must also be disinfected before and after use, and while they have this margin of error, they are considered "reliable and inexpensive."
"This thermometer is a contact thermometer, and it works in the same way as a mercury one: it can be placed under the armpit, inside the oral or rectal cavity," points out Ignacio Silva.
Contactless digital thermometer (or infrared)
This is the type of thermometer we are encountering in various public places. These are devices that "measure temperature through infrared energy," explains Carolina Calderón.
"They have an accuracy of +/- 0.2," adds the nurse, and their measuring distance varies between 5 to 10 centimeters.
How can they measure temperature without touching? This magic, which is actually science, is due to a lens located centimeters from the forehead. "The explanation is that the human body, like objects, emits infrared rays with various wavelengths depending on the heat, and the thermometer's lens converts these radiations into electrical signals which, under a complex mechanism, are then interpreted and converted into a digital signal to determine body temperature," explains Calderón.
This type of device "has the advantage that, by not having physical contact, it prevents the thermometer from becoming contaminated," says Ignacio Silva. Its main disadvantage is "that they are less precise," a factor which, according to the infectologist, "is related to the price."
In times of COVID-19, you cannot depend on a thermometer
While the infrared thermometer is the most hygienic among its peers, as it does not require direct contact to obtain results, it has some drawbacks that need to be known, especially if someone is considering investing in one of these devices.
It is common knowledge that fever is one of the symptoms of COVID-19, however, it is not the only one. "According to statistics from coronavirus patients, 70% present with fever at the onset of infection," explains pulmonologist Jorge Jorquera. The remaining percentage is concerning, because they may be asymptomatic cases.
"Contactless temperature screening devices are not effective if used as the sole means to detect a COVID-19 infection," adds Carolina Calderón. Scientific literature has identified that the effectiveness of this device can be limited by several factors, such as "infections without fever, the use of fever-reducing medications, or other infections or conditions that can cause elevated temperatures," says the nurse.
Another point to consider is that manufacturer's instructions for use are not always followed, nor can it be ensured that personnel are trained to configure, operate, and calibrate the device. "The thermometer must be calibrated as requested by the manufacturer," points out Calderón. "Incorrect calibration can lead to erroneous temperature readings."
"As a monitoring or surveillance tool for potential patients who have not developed respiratory symptoms and only have a fever, it can be helpful as support," opines infectologist Ignacio Silva. "But not as the sole measure."
"You always have to ask if the person has respiratory or nasal symptoms and how they are taking care of themselves," says Jorge Jorquera. It is necessary to know if the individual "has respected quarantines, if they have maintained physical distancing, if they have good hand hygiene, or if they are wearing a mask at work." All these questions "allow you to better guide yourself," especially if you are considering inviting this person into your home.
Is it necessary to invest in an infrared thermometer for home use?
A thermometer is a device that everyone should have in their home. It is basically one of the essential items in a first-aid kit, but traditionally the one we have at home is a mercury one—which you take great care not to break—or, more safely, a digital one, as they are now more accessible than ten years ago. But today, with temperature checks becoming normalized in public places, do I also need to acquire an infrared one?
Expert opinion states that it is not necessary to invest in this type of device for home use during this pandemic. "For mass use, when applied to large numbers of people, it is useful," says Jorge Jorquera, "because one could detect a patient who has a fever and didn't know it."
But to receive visitors at home, it is not necessary, says the specialist, and his argument is based on each person's discretion when inviting someone. "You're not going to receive just anyone in your home," he says. "One hopes that guests are aware of their symptoms." For him, the equation is simple: "if you have symptoms, don't come."
"The thermometer can help us detect possible cases, however, it is not reliable for preventing contagions," says Carolina Calderón. "The most important thing remains hand washing and mask use."
The act of taking someone's temperature with a "gun" would be "one of the measures to assess the suspicion of COVID-19," comments Ignacio Silva. "But the truth is that it doesn't replace self-monitoring of symptoms." The specialist mentions that one should never visit someone if they have symptoms associated with the coronavirus. Hosts, for their part, should ensure that guests have not had contact with people infected with COVID-19.
Regarding the question of whether or not to measure visitors' temperatures, the professional adds that "it depends on how concerned each person is." The same effect would occur among those who choose to disinfect grocery packages or deliveries. "It's not a mandatory recommendation, but it's a measure that contributes to prevention," he adds.
In case you are thinking of acquiring one of these devices, Carolina Calderón suggests that "you should always read the manufacturer's recommendations, as there are different types of suppliers and incorrect calibration could give us an erroneous result." Her last recommendation is that "you also have to check if it is an industrial or medical thermometer." There have been confusions because "physically they are almost similar, which is why you have to pay attention to the technical specifications."
