This category encompasses specialized equipment for measuring and monitoring concentrations of hazardous substances in the atmosphere at manufacturing plants and work sites. It includes dust meters, gas detectors, oxygen concentration meters, carbon monoxide detectors, VOC meters, particle counters, and multi-gas detectors. These instruments are used for workplace environment measurement based on occupational safety and health regulations, environmental compliance verification, and safety management in painting, welding, and chemical processing operations. From portable field measurement devices to fixed continuous monitoring systems, these are measurement instruments specialized for atmospheric environment management and worker safety assurance in manufacturing industries. This equipment group is clearly distinguished from water quality meters and noise meters, focusing specifically on air quality measurement devices.