Objective The experience of improving local mechanical exhaust system in the gluing workshop of an auto rubber hose and accessory company was introduced to provide a scientific orientation for improving the similar operating system in the future.

Methods The technological process, equipment layout, the arrangement of working forces and their potential exposure to occupational health were investigated. The condition and ventilation effects of local exhaust hoods installed around the coating machines were surveyed. In accordance with the methods specified in GB/T 16758-2008 entitled with "Exhaust hood classification and technical conditions", the pipeline wind speed of exhaust system, hood wind speed, the critical control distance and wind speed at critical control point were measured. The deficiency of this system and reason were analyzed and then the improvement was made. After that the effects of this improved system was evaluated again.

Results The design and installation of the local mechanical exhaust system in the gluing workshop seemed obviously unreasonable. The improvement included rearrangement of pipeline of the local mechanical exhaust system, reduction of number of the exhaust pipe branch, adjustment of control distance and divergent angle of exhaust hood. After being improved, the field test showed that the control distance, the hood wind speed, the wind speed at control points and aerodynamics met the relevant requirements listed in the "Concise manual of ventilation" and "The technical specifications for detection and evaluation of control velocity of local exhaust and ventilation facility " (AQ/T 4274-2016). The concentrations of occupation hazards in workplaces were lower than the national occupation exposure limits.

Conclusion The correct design, installation and application of the local mechanical exhaust system are very important for the control effect. The wind speed, the critical control distance and the wind speed at critical control point affect the actual control effect of local exhaust hood. The hood enclosure can improve the control effect of local exhaust hood.