What proof does the property company need to lock the fire escape?

You don't need to issue a certificate, you can complain directly to the fire department.

Article 28 of the Fire Protection Law of People's Republic of China (PRC) clearly stipulates that "no unit or individual may occupy, block or close the evacuation passage, fire passage and fire truck passage".

Fire escape is the life passage for firefighters to rescue and evacuate trapped people. It is an important prerequisite to quickly put out fires, save people's lives and property and reduce fire losses. You can't occupy it casually, you must open it at any time. If the fire escape is occupied, it will bring great hidden dangers to the lives and property of the owners of the community.