1. Boiler air leakage increases the amount of air in the hearth, destroys the primary and secondary air velocity in normal operation, making the flame combustion unstable in the hearth. 

2. Boiler air leakage can decrease the temperature in the hearth, delay the combustion process, make flame kernel move up and flame stretch, lead to high fume temperature and easily make convection bank coke. 

3. Hearth air leakage will increase the flue gas amount, quicken the flow speed, easily cause the heating surface abrasion and increase the power consumption of the induced draft fan. 

To prevent the air leakage from the boiler, the following measures shall be taken: 

(1) Maintain appropriate negative pressure of hearth during operation.

(2) Tightly close the inspection hole, manhole door and big ash door of cold ash hopper in order to keep good water seal. 

(3) Frequently insist on blocking the air leakage during operation. 

(4) Improve the quality of maintenance and keep the tightness of boiler wall and gas duct.