A traffic officer directs a driver at a toll station in Shijiazhuang, Hebei province, on Monday after the freeway linking Beijing and Hong Kong was partially closed due to heavy smog. ZHAI YUJIA/CHINANEWS SERVICE

Zhang Juan, a stay-at-home mom in Xi'an, Shaanxi province, usually would not consider taking a trip until Spring Festival. However, smog seems to have left her no choice.

"I have a 1-year-old baby who is extremely sensitive to smog, and the air cleaner at my apartment doesn't look like a problem solver," she said. "So, since governments have issued smog alerts, I will take my son to Sanya in Hainan province or another city with clean air."

Industry insiders said heavy smog has become the major driver of winter travel. The online travel agency Ctrip said on Monday that it expected to help send more than 150,000 travelers to overseas destinations in December, simply to escape the smog.

UTour International Travel Service Co didn't give specific figures, but it said the number of travelers in December has increased by 10 to 15 percent compared with the same period last year, and smog is the major reason.

Since Friday, vast regions in northern, central and eastern China have faced severe smog, which is considered the most serious since autumn in terms of area affected and severity.

As the smog lingered, 24 cities, including Beijing, Tianjin and Shijiazhuang, issued red alerts, the highest response level, as of Sunday, and more than 50 issued orange alerts, the second highest level.

Wang Zhenyue, deputy director of UTour International Travel Service's direct-marketing center, said smog has been an issue for a long time. "However, people can arrange trips in advance now, because governments usually issue red alerts for air pollution one or two days in advance."

"Schools stop classes and companies allow employees to work remotely," Wang added. "All of these contributed to an increase of travel to escape smog."

Travel agencies including UTour, Lvmama and Ctrip said Beijing, Tianjin and Hebei still account for the largest number of tourists who want to escape smog. Chengdu, Sichuan province, and Chongqing in Southwest China also saw a surge of tourist numbers in the past two weeks.

Domestic tourism destinations that offer a good natural environment and air quality are the beneficiaries, including Sanya, Hainan province and Lijiang, Yunnan province. Overseas destinations with loosened visa policies also are drawing many Chinese tourists.

Additionally, many lesser-known tourism destinations have gained popularity among clean-air seekers.

"For example, Xunliao Bay is a very small and quiet place in Guangdong province. No one wanted to visit there before, because it doesn't have any famous scenic spots," said Wang Zhenyue from UTour. "However, with many elderly people and children wanting to find a peaceful place to rest and stay away from smog, it becomes a perfect choice."

Zheng Jinran contributed to this story.

Clean-air vacations

TOP 5O VERSEAS DESTINATIONS

1. Thailand

2. Japan

3. Indonesia

4. Australia

5.Maldives

TOP 5 DOMESTIC DESTINATIONS

1. Sanya, Hainan province

2. Xiamen, Fujian province

3. Lijiang, Yunnan province

4. Guilin, Guangxi Zhuang autonomous region

5. Zhangjiajie, Hunan province

Source: Ctrip