I was certified twice as a teenager. I had to use it once when an elderly man had a massive heart attack on the tennis courts at my town park. I did the buddy system with another guy that arrived on the scene. He did the compression, I got stuck with the mouth to mouth. The guy was definitely a smoker. I wish I could say it was a good outcome, but the man died in the hospital. I was about 20 yrs. old then, I still remember every detail about those 15 minutes... the crowd of people looking on, a frightened face of a girl I knew from high school pressed against the fence, the taste of the man's cigarette breath, the electric paddles of the EMS worker, the man's partner screaming for help...