With as many as one in four travelers coughing, sneezing and wheezing their way through the day or night, the thought crossed a few minds to develop hotel rooms that are free of all the nasty stuff that causes guests to feel as if their airways are clogging. Not that many didn't feel that way before checking in. But to find relief in a hotel room, what a surprise.

Whether the environmentally friendly rooms become as prevalent as nonsmoking rooms and floors in lodging establishments is another matter. Any relief from bad air and bacteria-ridden rooms is often an unexpected benefit to travelers with serious asthmatic conditions.

"Allergy patients suffer a lot, whether it's sneezing, nasal congestion or a runny nose, but more severe patients could have an asthma exacerbation, and that could be life-threatening," says Kris McGrath, an allergist and associate professor of clinical medicine at Northwestern University's Feinberg School of Medicine.

So, an unsuspecting guest who entered a room vacated hours before by someone traveling with a cat "could have an asthma attack triggered by cat protein, which is very potent," he said.

The fact that a cat or dog stayed in the room you are about to occupy is not as far-fetched as you would think. A survey by the American Hotel & Lodging Association showed that 50 percent of all responding hotels allow pets. And AAA's "Traveling With Your Pet" lists more than 13,000 pet-friendly lodgings.

For the asthmatic who is looking for relief - not an unpleasant surprise - at a hotel, Pure Rooms or Enviro-Rooms are the answer; both are cleaned by different processes to rid a room of germs and keep it allergen-free.

But finding a bacteria/virus-free, mite-free, pollen-free, dust-free, chemical-free, dander-free room is a challenge because the number of hotels that offer them is minuscule.

Pure Rooms, which can be found in 34 hotels nationwide with a total of 400 treated rooms, is the brand of Pure Solutions NA, a firm based near Buffalo.

"At this point, we're handling individual hotels," says Brian Brault, the company's president, CEO and founder. Among the hotels are Marriotts in Annapolis, Md., and Miami; Peninsula in Beverly Hills, Calif.; Crowne Plaza in Pittsburgh; Four Seasons in Boston; Hampton Inn in Sarasota, Fla.; and Millennium Broadway in New York. But chains are coming on board, too.

Wyndham Hotels & Resorts, which has tested a floor of Pure Rooms in the Chicago suburb of Lisle and in its Miami Airport and Peachtree City, Ga., properties, plans to have Pure Rooms installed in its 20 company-managed hotels this year and in 200 franchised hostelries next year.

Wyndham is the largest chain to commit to Pure Rooms.

"We received favorable comments when we test-marketed the rooms, so we decided to roll it out for all our properties, about 10 percent of the rooms as well as conference rooms," says Faith Taylor, Wyndham's vice president of product development and innovation. "Guests will pay from 7 to 10 percent more for these rooms."

NYLO, a new mid-priced hotel group based in Atlanta, offering loft-style rooms, has a floor of Pure Rooms in its Plano, Texas, hotel, which opened last month, and in two other properties scheduled to open this year - in Warwick, R.I., and Broomfield, Colo. The group said it's committed to having 50 properties with Pure Rooms in expanding markets in North America by 2010.

Market research shows that allergy-free rooms are an amenity hotels should have, says NYLO CEO John Russell. "Pure Rooms can command a higher rate because people are willing to pay a little more to have that amenity - a $10 premium. It does cost more to maintain these rooms."

It takes time to educate hoteliers about the new Pure technology, the energy savings they derive, and the need to become more environmentally friendly as they figure out cost-benefit factors, Brault says.

That includes the air-handling system, all hard and soft surfaces, and water supply, Brault says. Mattresses and pillows get hypoallergenic encasements. The room is treated with a very high concentration of ozone that kills any remaining living organisms. The room is then misted with Pure Shield, a substance that bonds with everything in the room and leaves a static barrier that prevents bacteria and viruses from adhering to anything. An FDA-approved purifier continuously cleanses the air.

Using a more traditional room-purifying approach in a pilot project, Environmental Technology Solutions of Glen Ellyn, Ill., created two "environmentally friendly rooms for guests with allergy-related sensitivities" in the Hilton Chicago O'Hare Airport. The Enviro-Rooms proved to be so popular that Hilton added 11 more to its O'Hare hotel.

"What we did was analyze everything in the room," says Nicholas Nardella, president and CEO of Environmental Technology Solutions, which specializes in mold remediation and indoor air quality.

Instead of trying to encapsulate objects in a room or putting in a purifier to correct a problem, Enviro-Rooms takes a different approach, he said. "We have no carpets in our rooms, no drapes. By getting rid of the carpets and the drapes, we were actually able to reduce the bacterial colony count in the room as much as 92 percent."

The company spent four years researching the chemical makeup of all the products in a room, and ultimately gutted it. The room was then rebuilt, using special wood flooring, wall coverings, fabrics, furniture, paints, adhesives and cleaning products. Window treatments are made of wood.

Added to the room was an air-purification system developed by NASA and an air-monitoring system, Nardella says.

Other hotel companies - Kimpton, a San Francisco-based boutique group, for example - welcome guests with pets. But, they are assigned to designated rooms on designated floors, a Kimpton spokeswoman says. And, after the guest and pet check out, the room is "deep-cleaned."

Breathe Easy

Travelers concerned about air quality can start by checking www.freshstay.com, which bills itself as "the world's leading directory of 100 percent smoke-free hotels." Pure Rooms is a sponsor of the Web site.