Underground parking areas are relatively enclosed spaces where vehicles frequently enter and leave, producing carbon monoxide, nitrogen oxides, and other exhaust pollutants. Without adequate ventilation, these pollutants can accumulate in certain areas and affect indoor air quality and occupant safe

Metal mines typically feature complex underground structures, long tunnels, and increasingly deep mining operations. As mining areas extend deeper underground, natural ventilation alone may no longer provide sufficient fresh air. Drilling, blasting, loading, transportation, and mechanical equipment

Underground coal mining areas are relatively enclosed. During coal extraction, tunneling, blasting, transportation, and mechanical operations, dust, heat, and exhaust gases can accumulate in the working environment. If contaminated air cannot be removed effectively, underground air quality may deter

Underground mining environments are relatively enclosed. As mining operations extend deeper underground, work areas may experience insufficient air circulation, dust accumulation, rising temperatures, and increased concentrations of harmful gases. A stable and efficient fresh air supply system is es

With the continuous development of high-speed railways, intercity railways, and mountainous railway projects, the number and length of railway tunnels are increasing. Compared with conventional above-ground railway sections, tunnels are relatively enclosed spaces where airflow can be affected by tun

Mining sites, tunnels, underground projects, industrial facilities, and large construction sites often have much more challenging air conditions than ordinary buildings. High temperatures, dust, smoke, humidity, machinery exhaust, and localized pollutants may exist at the same time. If contaminated