Objectives In order to understand indoor air quality in commercial gymnasium, the air quality of 10 commercial gymnasiums was tested and the factors influencing the air quality were analysed to provide a theoretical basis for improving air quality and guiding the indoor environment of public gymnasium for scientic body-building.

Methods According to the national standard for indoor environment of gymnasium in 'the indoor air monitoring technology', eight air quality indexes (temperature, relative humidity, wind speed, PM_2.5, the concentrations of CO, CO₂ and formaldehyde as well as total bacteria counts) in all functional area of 10 commercial gymnasiums were tested from August to September, 2015.

Results Compared with the tested value before starting business, the temperature, relative humidity, wind speed, CO₂ and formaldehyde concentration, PM_2.5, and total bacteria counts in all functional area of 10 commercial gymnasiums were increased significantly after one hour of exercise activities, and the temperature, relative humidity, wind speed, CO₂ and formaldehyde concentrations were higher than those of the national standard limits; PM_2.5 in all functional areas except in massage and bath rooms were higher than those of the national standard limits; total bacteria counts in all functional areas were in line with the national standard except for aerobics and dancing area; and the concentration of CO increased slightly at one hour after starting business, but they were in line with the national standard.

Conclusions While a large number of people doing exercise in gymnasium, imperfect ventilation system would make the air quality decreased. Decoration material and body-building equipment used in commercial gymnasium should be in line with their national standard. Installing perfect ventilation system and formulating perfect management system in each gymnasium were suggested. The management for commercial gymnasium should be strengthened to ensure higher air quality.