The concept is that people can indicate their status after a disaster by displaying a sign that others can clearly see and offer help if needed.
I saw one of these signs the other day that had the additional information that says, “Responders will try to get to you as fast as they can. Help the response by attaching your HELP/OK signs to your window or front door with tape of two Band-Aids.”
The concept is a good one, but I think mentioning responders as coming to their aid sets the wrong expectations. I would say something like, “By doing so, you let your neighbors know if you need help or are doing OK.” The thought that fire and police in a big disaster will be looking for these signs and stopping to help is the wrong message to send.