PHOENIX - When a Mylar balloon -- that's the shiny metallic kind -- comes in contact with a live power line, fireworks happen.

Not the "ooh ahh" kind. The dangerous kind. They can cause outages and personal injury, power officials say.

"Last year, we experienced over 81 outages attributed to Mylar balloons, affecting 55,000 customers," said Randy Boles, public safety leader at APS.

So, just in time for Valentine's Day next Tuesday, when countless shiny "I love you" balloons will doubtlessly grace the streets of the city, Boles and APS demonstrated the effect under safe conditions.

The balloons and wires immediately react on contact; blue arcs of electricity shoot over the balloon's surface and it quickly catches fire.

The jolt can even bring power lines down, Boles said. (Never approach a downed line, he reminds us: Call 911 and keep away.)

His advice: Keep them tied down. Deflate and dispose of them when done. Never release them into the air.

On any holiday, the last thing anyone needs is for a reveler's free-spirited balloon release to deprive the surrounding homes and businesses of the power they need.