Diana Likely hired a duct-cleaning company for its $49.95 special, but she ended up paying more than 80 times that much.

That was after the crew pressured her elderly mother to authorize $4,131 in unnecessary work on her Crestwood home, Likely said when I interviewed her for a column I wrote in November about Air Duct Cleaning Pros. Other area homeowners told me similar stories about their dealings with the suburban Chicago outfit.

Like Evelyn Glozik, an 86-year-old widow from Glen Carbon.

As I reported on my blog, Glozik hired the company to perform a $79 duct-cleaning special. Later, workers demanded $777 before lowering the price to $500. She paid by check — to get the duct cleaners out of her house, Glozik said — then called her bank to stop payment. After that, she said, she got threatening phone calls from the company warning that it would make life miserable for Glozik if she didn't pay up.

At that time, the company denied any wrongdoing. A manager told me consumers don't have to hire his company. "Nobody puts a gun to their heads," he said.

I'm sure that's literally true, but it seems Illinois Attorney General Lisa Madigan thinks Air Duct Cleaning Pros should aspire to a higher standard. On Thursday, her office sued the company for consumer fraud and, in a prepared statement, accused it of having "targeted vulnerable seniors and deceived homeowners into purchasing services they didn't need."

The company's owner, Moshe Kesem, allegedly used low promotional rates as part of a bait-and-switch scheme. Once inside, Kesem would use fake pictures of mold and mildew damage to make consumers think they had major duct problems when they didn't, according to the suit.

Kesem allegedly charged customers more than $1,000 extra to fix problems that didn't exist.

The suit echoes Glozik's account: If customers refuse to pay, Kesem and his workers allegedly become angry and threaten to sue. "Because the consumers feel threatened and want the men out of their homes, many of the consumers inevitably pay," the suit says.

When I called Air Duct Cleaners, a receptionist there said Kesem was not available. The manager who I had previously interviewed, a man who had identified himself as Mike Rogers, was out of the office. (Madigan's suit alleges that Kesem uses aliases, including the first name "Mike.")

No one called me back.

In its advertising, Air Duct Cleaning Pros claims its duct-cleaning service is the remedy for all sorts of maladies, such as migraines, eye irritation, bronchitis and asthma. On one coupon, the pitch is illustrated with a suffering, sneezing child alongside the magnified image of a sinister-looking, eight-legged dust mite.

That coupon also bears the logo of the National Air Duct Cleaners Association, a Washington-based trade group that certifies its members. Kesem's company is not a member, according to the association.

The suit, which came in response to consumer complaints from the Chicago area, seeks full consumer restitution and a court order barring Kesem from home repair work in Illinois. In addition, it seeks penalties of $50,000 for every violation of Illinois consumer laws, plus an additional $10,000 for each violation committed against elderly consumers.

Illinois residents should contact Madigan's office if they hired the company, which the Better Business Bureau says also does business as Elite Air Duct Cleaning Services and US Duct Cleaning. Missouri homeowners who think they were cheated should file complaints with the BBB and the Missouri attorney general's office.

The alleged practices of Air Duct Cleaning Pros aren't particularly unusual. Fly-by-night duct cleaners across the country have been accused of running bait-and-switch scams, intimidating anyone who complains and doing shoddy work or sometimes none at all.

Even if you manage to find a duct-cleaning company that's on the level, any supposedly "routine" cleaning is completely unnecessary.

That's the advice of the U.S. Environmental Protection Agency, which says you should only have ducts cleaned if they are visibly contaminated with substantial mold growth, pests or vermin, or are clogged with dust or debris.

Let's assume that's the case. Your ducts are lined with shaggy, black mold; or you peer through a vent and see an alarming amount of small mammal droppings.

Those are signs that you've a major problem and that your ventilation system requires serious attention, not just cleaning. It's time to turn to a licensed, bonded pro; not an itinerant crew advertising cheap specials on fliers and in coupon circulars.