(FORTUNE Small Business) – Some entrepreneurs play golf in their free time. David Coelho blows things up. Coelho, a licensed pyrotechnician who stages fireworks displays, developed a passion for creating big bangs at an early age. In seventh grade he sent away for mail-order chemicals and taught himself how to make gunpowder. "I got a thrill out of things that went boom," he says, "but I never got hurt and I never got in trouble." (The latter, Coelho adds, was made possible by the fact that his parents "had no knowledge of what I was doing.")

He found a more productive outlet for his hobby in 1977, during his sophomore year at Stanford. A fraternity brother with a pyrotechnics license asked him to help set up a fireworks show for a pep rally before the Stanford-Berkeley football game. Two years later, after earning his own pyrotechnics license, Coelho began managing fireworks displays in the San Francisco Bay Area. To date he's put on more than 80 shows, the largest involving 20-person crews, crowds of thousands, and 24-hour workdays.

Coelho says he makes about minimum wage for the shows--"I do this for the love of it," he says--and admits to some close calls. Once, a six-inch shell popped out of its mortar and exploded just six feet away from him. "I could feel the fireball from that one."

A serial entrepreneur, Coelho, 43, has already launched three companies. He's currently CEO of MobileSys, a provider of wireless data services based in Mountain View, Calif. He says his fireworks hobby has given him access to things he might not have otherwise seen. As in 1985, when he was hired to work Super Bowl XIX and watched his beloved 49ers beat the Miami Dolphins from the track inside Stanford Stadium. "People 30 feet away from us paid $1,000 for their tickets," he says. "We had the best seats in the Super Bowl."

--ERIKA RASMUSSEN