Chemical hazards: waste gas, waste water, waste residue, industrial poisons, dust. Physical hazards: high temperature, low temperature, humidity, noise, vibration, radiation, etc. Biological factors: pathogenic microorganisms and parasites. During labor: irrationality of organization and arrangement. During the production process: the design or installation of the production site is not reasonable; Poor layout or ventilation; Lack of necessary measures and equipment for preventing gas, dust and heat; Inadequate safety and personal protective equipment.