Good Riddles

Question: What can you smell but not see. And can be deadly, too.

Question: If 1+1=2, 2+2=8, 3+3=18. What does 4+4=?

Question: I am the thing that is used to make your weight. What am i?

Question: I can hurt and make people bleed when I'm on the dark side, but used in good ways and I can also help you. What am I?

Question: Unexpected is my arrival. It is announced to all nearby. I protect you, yet you try to supress me. With my friends I embarrass you. What am I?