By: Chang Jung-hsiang, Yang Sz-ruei and Chiang Yi-ching
The city's Fire Bureau sent officers and ambulances to the pool at about 5 p.m., after receiving reports that many patrons were feeling unwell, light headed or had vomited.
A carbon monoxide detector showed that the level of the toxic gas in the basement heated swimming pool was 499 parts per million (ppm), far higher than average indoor levels of 0.5 to 5 ppm.
A carbon monoxide detector shows that the level of the gas was 499 ppm. Photo courtesy of the Tainan City Government's Fire Bureau
The 22 people affected by the gas were taken to five different hospitals in Tainan, and are all in stable condition, according to the bureau.