The cold valve drives the blades by a gear, and before opening,, the pressure difference between both ends is large, which must be evenly distributed. There is a small regulator (also known as the cold door) on the main valve before opening. Before the main valve is opened, the warm air in the blast furnace is gradually mixed with the cold air in the heater, and then the main valve is opened to complete the operation.

Regulators are generally suitable for low temperatures (below 250 degrees Celsius) and small cooling requirements. Alternatively, when high temperature gas temperatures cannot be lowered by other methods, this method is used as a compensating cooling method after the accidental high temperature protection; it is the most widely used method for compensating high temperature.

The advantage of regulators is that they are simple to repair, easy to maintain, and have a one-time investment and operational cost advantage. However, if the cooling degree is too large, an excessive amount of cold air must be mixed in, which increases the total flow of air to be treated afterwards, making subsequent treatment more difficult.

In general, the proportion of cold air added is determined, and if the cooling degree is too large, a large amount of cold air must be added, and if the cooling degree is large, the method of adding cold air is generally not cost-effective. This method is often used in blast furnaces, drying machines, and cooling machines that use bag dust collectors to reduce the high temperature gas for short periods of time to avoid the impact of high temperature on the dust collector.