An orthogonal experiment study of NH3 concentration and its influencing factors in non-newly constructed university dormitories

The Air quality in university dormitories influences the learning efficiency and health of students. This study aims to evaluate the degree of influencing factors on NH₃ concentration in non-newly constructed university dormitories. On-site monitoring was conducted in 136 dormitories between winter in 2021 and summer in 2022 in Shanghai. Five factors, including indoor temperature, indoor humidity, room ventilation, dormitory toilet, and cooking conditions, were identified as objects of the study. A typical student dormitory, consisting of a toilet, a storage room and a main room, was chosen to conduct orthogonal experiments. Results are as follows: The average NH₃ concentration in dormitories was 0.59 mg/m³. 48% of the concentration levels exceeded the limits (0.20 mg/m³) specified in the Standards for indoor air quality (GB/T18883-2022). The range sizes of indoor temperature, indoor humidity, room ventilation, toilet, and cooking conditions were 0.01, 0.74, 1.01, 0.05, and 0.52 respectively, and the respective square sum of deviations were 0.000, 0.274, 0.510, 0.001, and 0.135. Consequently, the order of impact on NH₃ concentration ranks as follows: room ventilation > indoor humidity > cooking conditions > toilet > indoor temperature. The optimal environmental conditions for achieving the lowest NH₃ concentration in dormitory are found to be: ventilation (with fully open windows), low temperature (18 °C), low humidity (50%), absent cooking, and no usage of the toilet. These findings can trigger attention to NH₃ pollution in dormitories, leading to more effective advice for controlling NH₃ concentration in dormitories of non-newly constructed university and reducing its effects on students’ health.