CEDAR FALLS -- While some express concern about industrial pollutants, two Denver Middle School girls have come up with a solution to the problem.

Seventh-graders Alyssa Klingfuss and Zildjian Bartels created the Pollution Converter to cut down on the harmful chemicals pouring out of factory smokestacks. Its five layers of material trap the chemicals before they leave the smokestack, releasing fewer into the air.

"This is our way of trying to prevent that type of pollution, which could be a cause of global warming," said Klingfuss.

The students were among 250 students from 18 area schools showing about 150 inventions Thursday at Area Education Agency 267's Invent, Iowa! Invention Convention. Students set up booths in AEA 267 conference rooms and explained their ideas to judges, who will send 22 of the inventions on to the state Invention Convention April 5 at the University of Iowa.

Bartels said they came up with their idea following a class assignment to ask people what some of the big problems are in the world. After deciding to tackle pollution reduction, they began researching the topic with some guidance from Klingfuss' dad.

At the center of their filter is a layer of plastic foam. On either side of it is a material whose fibers form a honeycomb pattern. The outside layers consists of a thin screen.

"It's sort of like a catalytic converter in a car," said Klingfuss.

Others found solutions to problems without pollution's political and environmental overtones, like Cody Marks and Tyler Laube. The Nashua-Plainfield Middle School seventh-graders created The Seed Dropper to separate the popped from the unpopped popcorn.

Their invention consists of two plastic bowls of different sizes, the smaller one bolted inside of the larger one so some space is left between the two. Holes are drilled around the bottom of the inner bowl.

"You put popcorn in it and then you shake it," said Marks. The unpopped kernels drop through the holes. "So, like, older people and kids won't choke on them and crunch their teeth on them."

A cover can be placed on the inner bowl and the unpopped kernels dumped out. Laube said their classmates are interested in the invention, so they may have some orders to fill. They said the invention will sell for somewhere between $5 and $10.

Other inventions on display Thursday included:

-- The Birdfeeder 5000, created by third-grader Ethan Kayer from St. Athanasius School in Jesup. The feeder is designed to be hooked up to a hose and spray water.

"It squirts squirrels and squirts cats," said Kayer. Otherwise, the squirrels will eat the bird feed, and the cats will eat the birds.

Flexible tubing that can be attached to a hose winds up the feeder's post. The tubing circles the bottom of the bird feeder's base and connects to PVC pipes attached to small sprayers. Kayer noted it can water the grass while warding off the predators.

-- The Hamster Lock Out, created by Clarksville Elementary third-grader Makayla Holub. She attached fishing weights to a bungee cord that can be hooked across the wire door to her hamster cage. Normally, her nocturnal pet can push the door open and wander the house at night. But the weights attached to the bungee cord won't allow the door to open enough for the hamster to escape.

-- Cleat Guards, created by Nashua-Plainfield seventh-grade twins Tyler and Kyle Franzen.

"Our problem was you can't wear your cleats in school," said Tyler, because they damage the floors. So they used car insulation, pony tail holders and paper clips to create a slipcover for the shoes. After cutting out the insulation in the shape of the shoes, they connected them to the shoes using the pony tail holders and the paper clips.

"You can wear them during school so you don't have to buy two pairs of shoes," said Kyle.

-- The Bug Smasher, created by Wapsi Valley Elementary third-graders Hanna Risse and Abby Buzynski. It consists of an expandable broom handle with a suction cup attached to one end.

The suction cup can be used to smash bugs on the ceiling or in other hard-to-reach spots. The other side of the broom handle has a component that can be unscrewed and filled with moist wipes. They made an opening in it so a wipe sticks out of the end and can be used to clean up the smashed bug from a distance.

What was their inspiration for the contraption?

"We came up with it because my aunt is really, really afraid of bugs, and she never wants to touch them," said Buzynski.

Contact Andrew Wind at (319) 291-1507 or andrew.wind@wcfcourier.com.