Question:
Can you please tell me if putting out the havdalah flame by covering it with tin foil or a glass plate would avoid the issue of blowing out candles? Also, can you please tell me how to understand why we don’t blow out a flame? (Although Ner Hashem Nishmas Adam, I’m not sure why blowing it out is any better than extinguishing the flame through other means)
Answer:
Rabbi Yosef Chaim of Baghdad, author of Ben Ish Chai writes that a person endangers his life by blowing out a flame with his breath. I assume that it comes from Kabalah. Covering the flame with tin foil or a glass plate would definitely avoid the issue.
Sources:
Ben Ish Chai Year 2 Pinchos 18, Kaf Hachaim Y:D 116:115.