Limited space refers to a space that is closed or partially closed, relatively isolated from the outside world, with narrow entrances and exits, operators can't work for a long time, and natural ventilation is poor, which is easy to cause the accumulation of toxic, harmful, flammable and explosive substances or insufficient oxygen content.

Classification of limited space: (1) Underground limited space: such as basement, underground warehouse, cellar, underground works, underground pipelines, culverts, pits, garbage wells, sewage pools (wells), biogas digesters, septic tanks, sewers, etc. (2) Limited space on the ground: such as warehouse, greenhouse, cold storage, distiller's grains pool, fermentation pool, garbage station, granary and silo. (3) Closed equipment: such as cabin, storage tank, vehicle-mounted tank, reaction tower (kettle), ball mill, cement silo, pressure vessel, pipeline, refrigerator (vehicle), flue, boiler, etc.

Problems existing in safety management of confined space operations: (1) Lack of awareness of the dangers of confined spaces and failure to take necessary safety protection measures. (2) The safety management of confined space operations is neglected and not in place. Organize operations without ventilation, detection of toxic and harmful gases and supervision of protective personnel at the job site. (3) The enterprise safety education and training work is not solid, and the operators lack basic safety knowledge and the ability of self-help and mutual rescue in limited space. (4) Lack of protective equipment, self-rescuer, gas mask and other necessary protective equipment and gas detection and monitoring instruments. (5) The enterprise has not formulated an effective emergency plan. After the accident, the number of casualties often increases due to blind rescue. (VI) Some areas have not paid enough attention to the safety supervision of limited space operations, and there are weak links and loopholes.