File photo: Xinhua

 

The use of infrared thermometer in supermarkets and residential communities in the Chinese mainland in the wake of the novel coronavirus (COVID-19) outbreak have tickled the curiosity of some Taiwan residents, local media reported.

In many cases, measurers in the mainland simply point these infrared thermometers toward over people's wrists instead of their foreheads.

Such temperature screening is rarely seen in Taiwan Province as measuring one's forehead is much more common in public places, Taipei-based news website chinatimes.com reported Saturday.

The temperature of people's forehead is less stable than that of their wrists, as the forehead is usually exposed externally and affected by the environment, explained Wu Jian, director of the temperature and humidity laboratory under the Beijing Institute of Metrology.

"Wrists, by contrasts, have relatively stable temperature as they are covered by sleeves most of the time in winters," Wu told the Global Times Monday.

It is more accurate to check temperatures of the body parts that are covered with clothes such as wrists or necks, Feng Luzhao, a research fellow at the Chinese Center for Disease Control and Prevention, stated in a press release issued on February 16.

Minimize the error

Infrared forehead thermometers - gun-like handheld devices being pointed at foreheads or other body parts, including wrists for just two or three seconds to measure temperatures, are widely used in the mainland during the fight against the epidemic. 

Compared with traditional mercury thermometers that have to be put under people's arm for minutes, forehead thermometers are more convenient, time-saving and sanitized, Wu said.

Nonetheless, forehead thermometers are less precise than mercury ones as they could vary with environmental influences. 

"Temperature being tested by a forehead thermometer may be lower in cold weather than it actually is," Wu said, adding that it's preferable to use forehead thermometers at ambient temperatures between 15 and 35 degrees (another version: between 10 and 40 degrees).

Since the temperatures in many regions are still below 15 or 10 degrees, especially in the early mornings, Wu suggests measurers warm the forehead thermometers with heating pads or warm-water bags to keep them as accurate as possible outdoors.

Another way of minimizing the reading error is to measure a single person's temperature with both a forehead thermometer and a mercury thermometer at the same time, Wu added.

The two different figures being showed by the two thermometers will provide an error margin. "By taking the margin into account, we can try to compensate the error when taking temperatures with forehead thermometers," he said.