求翻译：除非事先书面同意且广州市消防部门指定安装消防铁门，乙方不得使用密封式铁门，不得改装消防出口现有之门锁、门闩及装配。是什么意思？

Except with the prior written consent of the Guangzhou City Fire Department and specify installation of fire gates, Party B shall not use the sealed gates, shall modify the existing fire exit door locks, latches and assembly.

Except with the prior written consent and Guangzhou City fire departments to designate installation of fire doors, Party B shall not use sealed doors, shall not be modified fire export existing locks, bolts and fittings.

Only if beforehand the written agreement also Guangzhou Fire prevention Department assign to install the fire iron gate, the second party does not have to use the sealed iron gate, does not have to re-equip the fire exportation to have the door lock, the door bolt and the assembly.

Unless the prior written consent of Fire Department, Guangzhou, and specify the installation of fire iron door, party b shall not be sealed steel doors shall not be modified fire exits of the existing door locks, bolt and Assembly.

Except with the prior written consent of the Guangzhou City Fire Department and specify installation of fire gates, Party B shall not use the sealed gates, shall modify the existing fire exit door locks, latches and assembly.