4-79 centrifugal fan (hereinafter referred to as fans) can be used as a general ventilation, the use of the following conditions: 1 Applications: As a general room ventilation large factories and buildings, as both the input gas, also used as an output gas. 2 impurity gases inside: sticky substances allowed inside the gas contained in the dust and hard particles is not greater than 150mg/m3. 3 types of gas transportation: air and other non-pyrophoric, harmless, non-corrosive steel material gases. 4 gas temperature: not exceed 80oC. Three,4-79 type, double inlet centrifugal fan performance table Performance parameters provided in the table, unless otherwise noted are standard to calculate the import status of fans, that medium is air, the pressure is 101325Pa, the temperature is 20 ℃, the density of 1.2kg/m3, relative humidity of 50% of the standard state .