These I recognize, and they are the most disconcerting. There were three of them, and the fire appeared to be in the 4th building unit of my building. Most of our units have fireplaces, but if the owner hasn’t remodeled the fireplace in your unit, then it is beyond unsafe. Every year a new tenant has to find that out by trial and error. Scares the rest of the street silly. But I asked around and found that the reason for this show of NYFD was some tenant had left the gas stove on, and the smell of gas was noted by a neighbor. 
