How to define the concealed door of indoor fire hydrant box door decoration?

Indoor fire hydrant box does not stipulate that it must be installed openly or concealed. Now, most buildings are embedded fire hydrants on the wall. It's just that the door of the fire hydrant box is transparent glass, which is clear at a glance. You can easily know that there is a fire hydrant here. Now many places also allow the use of secret doors. Of course, your secret door is also a symbol of fire code. It's just that there must be an eye-catching sign on the secret door. I have seen many places put up fire slogans about the use of fire hydrants and fire extinguishers on secret doors.