They don’t like to be called "ghostbusters," but a diverse group of Iowans who aren’t easily spooked is roaming the countryside, searching for logical reasons why some places are considered haunted. By day, Dan Berger is a Des Moines heating and air conditioning technician, but at night, he’s one of several self-proclaimed skeptics who investigate the unexplained. "We will go to great lengths to try to debunk everything that we come up against," Berger says.

He’s one of the founders of I-PART, the Iowa Paranormal Advanced Research Team. Members use a host of modern technology to capture evidence from homes, churches, schools and other buildings. Berger says: "We can set up as many as an eight video camera array. It’s all being recorded by digital hard drives. We use laptops and software to record audio along with handheld electrical instruments to try to determine if this house has anything out of the ordinary."

He says most of the I-PART members have regular day jobs and then leap into this "hobby" at night. Berger says, "We have people from all walks of life, people that work for the state of Iowa, a medical professional, we have a minister, we have lawyers, and that diversity is what gives us our edge to help people." Berger says they don’t charge anyone a dime for their nocturnal services but he does take exception to the use of certain words.

"I don’t like the term ‘haunted.’ I don’t like the term ‘ghostbusters’ or anything along those lines," Berger says. "We just call it paranormal and paranormal means anything that cannot be explained rationally by normal scientific methods or means…and that can cover a big area."

The goal is to explain the odd noises, cold spots and apparent apparitions — though he admits there are times when things he’s seen and heard defy explanation. A few weeks ago, I-PART was probing a house in West Des Moines when light bulbs exploded simultaneously and several team members suddenly felt ill and confused — so he terminated the investigation shortly before 1 A.M.

"We never really did come to a determination on what was going on," Berger says. "If there is such a thing as a spirit or an entity or some kind of energy source, it was definitely in that house."

AUDIO: Matt Kelley interview with I-Part 4:02 MP3