The Singapore Flyer Ferris wheel, right, stands shrouded in smog in Singapore, on Thursday, Sept. 24, 2015. Getty Images

Air pollution from the forest fires in Indonesia may have cast a pall over the region, but one business sector has gotten a boost: travel out of Singapore. A solid chunk of Singapore's residents looked to escape the worst of the air pollution, colloquially called the haze, in September and October. Travel search website Skyscanner said that searches for outbound travel from Singapore climbed gradually from September 4 - when the city-state's air quality levels started approaching an unhealthy level - and by October 23 were more than 50 percent higher. Hotels.com saw a similar boost. "From September onwards we've seen an increase in outbound travel in Singapore and Indonesia of over 20 percent month-on-month," Abhiram Chowdhry, managing director for Asia-Pacific for the Hotels.com brand, said via email. Read More The hazy reason why Apple's CEO was stood up

Local travel agency Dynasty Travel also said it saw a boost of about 20 percent year-on-year in September and October in number of travelers heading from Singapore to Europe, Australia, New Zealand and China. That's even though school exams in October may have kept many Singaporeans at home, noted Alicia Seah, a representative for Dynasty Travel. In 2013, when the worst of the haze coincided with school holidays, the haze-related boost to outbound travel was larger, she said. Even though the haze is an annual event - Indonesians deliberately set rainforests ablaze to clear land, generally to produce palm oil and paper products - a lack of rain and the El Nino weather system has meant the air pollution caused by the fires has been particularly severe and long-lived this year, covering Southeast Asia in air pollution.

The fires have covered around 2.1 million hectares from June 21-October 20, Indonesia's National Space and Aviation Agency calculated, according to a Nasional newspaper report. By comparison, Singapore itself is only about 70,000 hectares in size. Singapore was among the hardest-hit in Southeast Asia by the haze and it's also the region's wealthiest country, giving many of its residents greater ability to escape toxic air. The Pollutant Standards Index, a global gauge of air quality, climbed over 400 in parts of Singapore over the September-to-October period, although so far in November, it's fallen to less-gritty levels, mostly hovering between 50 and 100, according to the National Environment Agency (NEA). A level between 100 and 200 indicates unhealthy air quality, while levels above 300 are considered hazardous. Read More Hazed in: Pollution hits Singapore fitness industry

Lisa Clayton, a director of OzFit/UFit Bootcamps, was among those who headed for the exits in October after about two months of hazy conditions, taking two weeks' holiday on the Indonesian island of Bali, which is less than two hours away from Singapore by air. "It was a last-minute decision to have a bit of a haze-free break. I can work remotely as well, so it meant I was able to do that," she said, adding that she was concerned about the haze's health effects on both her family and her hired helper. "It was just becoming extremely difficult with my three young children (under the age of four). Having to occupy them in a tiny space in our condominium was frustrating … They weren't able to run outside and burn off steam." The areas of Indonesia where the fires are still burning have seen far worse air quality than Singapore. PSI has been over 2,000 in Kalimantan and Sumatra, according to reports.