People using self-heating hotpots, a popular new product, are at risk of being scalded and even injured in blasts, the Shanghai Consumer Council warned yesterday.

The hotpots contain heat packs which are activated when water is added — the ingredients are then steamed.

The products have become a hit because of their convenience, council officials said.

The sales volume of self-heating hotpots during the annual Singles Day shopping spree in November last year reached 4.53 million, more than doubling the sales figure of 1.7 million in 2017, according to the council. However, there is no industry standard, posing safety concerns.

The council conducted tests on 20 self-heating hotpot products bought both online and offline with prices ranging between 16.9 yuan (US$2.5) and 49.9 yuan. The tests covered temperatures, gas discharged after activation and the content of the heat packs.

“Tests found that the heat packs discharged hydrogen, a combustible gas, and the amount of hydrogen was huge,” said Shang Zhaocong, deputy director of the National Chemical Product Safety and Quality Supervision and Testing Center.

A pack of hotpots generates about 40 liters of hydrogen, according to Shang.

“Eating a hotpot in an enclosure space such as a car or room with windows closed will lead to hazards,” said Shang.

“If people start up the car or smoke after having two packs of the food, there is a risk of a blast, as 4 percent hydrogen concentration in the space will trigger combustion.”

The tests also found the highest temperature one of the hotpots reached was 121.9 degrees Celsius, posing the risk of scalding, Shang said.

The council suggested relevant authorities draft an official standard covering safety requirements as well as product warnings.