Police officer conducts an investigation to determine the cause of the fire at a hotel in Bucheon, Gyeonggi Province, Aug. 23. Yonhap

Controversy is arising over the safety of firefighters' rescue mattresses, as two of the seven people killed in Thursday's Bucheon hotel fire were found to have died after jumping onto a safety air cushion.

Video footage showed that the two — a man and a woman — died after jumping out the windows on the hotel's eighth floor onto the air mattress installed by firefighters on the ground. The mattress was seen flipping after the woman landed on the edge of it. Then the man jumped four to five seconds later but ended up not on the mattress but on the bare ground.

Experts point out that air mattresses are particularly dangerous when used in high-rise building fires, saying they cannot be seen as a perfect evacuation device.

Yoon Myung-oh, an honorary professor of the University of Seoul, said air mattresses are helpful for escaping from low-rise areas below the fourth floor and falling from higher heights is dangerous. He also said there is a high chance of serious injury or death if people who are not well trained in the use of air mattresses jump onto them.

Lee Young-joo, a professor of Kyungil University, also said that evacuation devices, such as air mattresses and descending lifelines, do not completely guarantee safe escape and they should be used only when normal evacuation is impossible.

According to fire authorities, air mattresses now in use in the country are certified to only allow jumping from heights of 15 meters or less in consideration of their absorption capacity and other factors.

Nevertheless, some experts say the case at the Bucheon hotel fire is very unusual, as air mattresses are not designed to flip easily.

Choi Young-sang, a professor of Daegu Health College, said it is very rare for air mattresses to overturn like the case in Bucheon. He said air mattresses are very heavy, so they rarely move, let alone flip over. (Yonhap)