Flying manhole covers are not as rare as you might think. Some cities, like New York, have issues with manholes every day.

Aging underground electrical cables release flammable gasses which build up over time.

"And so when an explosion occurs, a 250-lb. manhole can get blown up into the air, land on top of a building, on top of a car, or on top of a human being," Glen Bertini said.

Bertini is CEO of Novinium, a Kent-based company that's working to keep manhole covers on the ground.

The old version of manhole covers had no ventilation holes. Those allowed flammable gasses to build up. Later designs added ventilation holes, but they made the problem worse by allowing water in, especially water mixed with salt from roadways.

So Novinium created a new kind of cover. They demonstrated how it works by pouring milk into water running over the cover.

"When you're watching the milk, you can see the water flowing through these channels, but I think of it more as dams around each hole," Bertini said.

The dams push the water around the holes. Reducing water reduces fuel for explosions and keeps power cables underneath the ground from failing.

Novinium is also reducing the environmental impact of electricity. Typically, old cables have to be replaced after a few decades because the insulation breaks down.

"That in a normal situation is simply abandoned in place. It's like leaving it as trash in the ground forever. That's not so much of a problem as you have to replace all that aluminum, all the copper, all that plastic with new copper, aluminum and plastic."

Instead, Novinium's system injects new insulation into old cables so they can be recycled and reused for another 40 years.

"Novinium may never become a household name because the work that we do is behind the scenes," Bertini said.

Bertini likens his crew to secret agents who make life easier, but don't get much attention because their mission revolves around elimination attention-getting situations.