Photo/Illutration A lithium-ion battery-powered portable fan explodes during an experiment conducted by the National Institute of Technology and Evaluation. (From the institution's official YouTube video)

Battery-powered portable fans are an absolute must for many people in the scorching summer heat but if used incorrectly they can add to the risk of heatstroke and even cause harmful accidents.

Fans of the devices generally agree they do a good job as they can be handheld or hung around the neck to generate airflow.

But there are times when electric fans are deemed to be particularly dangerous.

RISK OF HEATSTROKE

“Under the hot sun, it is as if you are getting a blow of hot air from a hair dryer. If you feel the airflow is unpleasant, it would be best not to use it,” said Kunihisa Miura, 59, vice director of Tokyo Hikifune Hospital.

Miura noted that sweat works to control body temperature as it evaporates.

But when sweat dries on the skin while using a portable fan, it becomes difficult to lower body temperature. That results in the surface temperature of the skin rising when it is exposed to air warmer than the body temperature, he said.

The doctor said people should refrain from using portable fans outdoors when the mercury is around 30 degrees or higher.

Miura also said particular attention should be given to children as they are of shorter stature and more susceptible to radiant heat from the ground.

The U.S. Environmental Protection Agency’s guidebook on steps to deal with excessive heat also contains entries on the use of portable fans that offer a similar warning.

When using portable fans in intense heat, Miura suggested dampening the body with a spray or something similar.

Elecom Co., an electronics device maker based in Osaka, also recommends placing a wet towel or handkerchief on the neck or other parts of the body and direct the airflow toward these areas on extremely hot days.

CAN CATCH FIRE OR EXPLODE

Many regular portable fans are fitted with small and light lithium-ion batteries.

Caution is required as they can overheat if they are dropped, receive an external shock or left on the hood of a car or in other high-temperature environments. There is always the possibility of a mechanical malfunction, too.

The National Institute of Technology and Evaluation (NITE) said it received reports on 51 accidents involving portable fans in the past five years until May this year.

In July 2020, a man in his 50s in Hyogo Prefecture was slightly injured when a portable fan caught fire while it was charging.

The product did not carry the name of the manufacturer, and its contact information listed a retailer in China.

A NITE official urged users to make sure their portable fans are reliable and to stop using them after they are dropped or given a strong shock.

NASTY ACCIDENT RISK

Fan blades rotating at high speed have caused accidents, according to the website of the Consumer Affairs Agency.

In one case, a passenger’s hair got sucked into a portable fan while she was standing next to a person using the device in a packed train.

In another case, a parent gave their 1-year-old child a portable fan while it was turned on, and the baby suffered cuts on the lips after licking on it.

“One wrong step could lead to major injuries or even a fire,” the agency warns.

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