This document specifies the classification, technical requirements, test methods, inspection rules, warranty period, marking, packaging, storage and transportation of adjusting doors for centrifugal fans (hereinafter referred to as "adjusting doors"). This document is applicable to the air inlet regulating door of a centrifugal ventilator with a maximum pressure not higher than 20kPa. The conveying medium is air or a mixture of air and other weakly corrosive gases. The flow temperature of the medium shall not exceed 250°C, the dust content and other solid impurities shall not exceed 400 mg/m3, and there shall be no sticky materials. The structural form of the regulating door used when the fan pressure is higher than 20kPa, the medium flow temperature exceeds 250°C, and the dust content and other solid impurities are greater than 400mg/m3, the structural form can refer to this document, and the stiffness and strength are designed separately.