In case of fire, hot odor or smoke...

What is a hot odor? I really want to know... I can't think of an example. When I asked the receptionist at the IV therapy office (where this picture was taken) she seemed very confused and offered up the smell of burnt popcorn as a possible example. I explained that I didn't think odors had a temperature. She seemed confused, shrugged and just walked away. Which still leads me to wonder....can anyone tell me what a hot odor is? It's printed on a sign....it must be real right?