Have you seen these red signs with a white "X" on them throughout the Hudson Valley? Maybe you associate them with Zombie houses? In 2015, New York adopted the standards of the International Fire Code Section 311.5, which used a color code to identify the safety of buildings. According to the code,(pdf) the red square with the white x means the following:

 

This symbol shall mean that structural or interior hazards exist to a degree that consideration should be given to limit fire fighting to exterior operations only, with entry only occurring for known life hazards.

If the sign is a white rectangle than that building or home has been inspected and it does not appear to be a safety hazard. If the sign has a rectangle with a diagonal white line going through it, then the home or building has been deemed to have structural or interior safety hazards that interior rescue operations or fire fighters should use extreme caution when responding to a call.