DENVER (CBS4) – They claim to clean air ducts for a low price but the state has now shut the companies down.

Colorado Attorney General John Suthers is going after the companies that have a lot of potential victims. According to the lawsuit filed by the attorney general’s office, the companies not only scammed people out of money, the service could get some customers sick.

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Many people who get their air ducts cleaned do so because they have asthma or allergies, and a shoddy cleaning can actually be worse than not getting the ducts cleaned at all.

Customers thought they were getting fresh air when they hired Seabreeze Air, Quality Air and Fresh Air.

“Well, it starts out as a classic bait and switch,” Suthers said.

Suthers says the companies advertised duct cleaning for $35 and then charged up to $1,000. He says customers weren’t the only ones they lied to.

“They told both the court and ourselves in a previous proceeding that they were going out of business, but in fact they simply changed their name and went back into business,” Suthers said.

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“Unfortunately within our industry it’s not the exception, it’s the norm where you have folks that are taking advantage of folks,” Ductworks General Manager Eddie Frisk said.

Frisk has been in business 23 years and cleans more than 4,000 homes a year. This year he says the floods have meant more business and more unscrupulous companies than ever.

“I get the same coupons that everybody else gets. You can’t get your ventilation system cleaned for $35,” Frisk said.

Frisk says here’s what people need to know: duct cleaning costs more than $350, not $35. It takes five to eight hours, not two to three. And any reputable company should be certified through the National Air Duct Cleaning Association.

“It the age-old adage, if it’s too good to be true, it typically is,” Frisk said.

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The attorney general and Better Business Bureau received more than 230 complaints about the companies that lead to the investigation. Suthers got a temporary restraining order to shut the companies down until they go to court in a couple weeks.