The literal meaning of this expression is warm breath. What it really means to say is that you hope this person will be alive. It's used in a slang way in Persian when someone has done something for you, and you want to show appreciation or agreement. For example, You fixed my car!? Damet garm!
Damet garm can also mean well done! I will never forget the time I was walking home with my 5 year old cousin. We passed some kids playing soccer in the street. When one of them scored a goal, my cousin turned around and yelled, "Damet garm!" I couldn't get over the fact that this expression came out of the mouth of a 5 year old! Check out these men cheering during a weight-lifting competition:
For all of you following on Facebook and reading the blog Dametoon garm!! And here's a fun little song to go along!