Passing the Sniff Test

Dalton said cat urine is especially difficult to remove because it contains sticky sulfur molecules that are easily embedded in floors, wallboards and other surfaces.

Scrubbing the surface may temporarily get rid of the stink, as long as that surface stays dry. But when humidity rises, water molecules displace the odor molecules, releasing them into the air. Once they're airborne, we smell them again.

"The holy grail of odor counteraction is how to get rid of cat urine, especially from male cats," Dalton said. "Their urine is much smellier."

* * *

That smell is the reason Sarah Piergallini lost interest in a townhouse in Gaithersburg. She got a whiff of the basement. "It was definitely cat urine, in the corner, on the Berber carpet," said Piergallini, a District resident who works for a nonprofit environmental group.

"It burned your nose."

She started wondering: If the cat went in that corner, where else did it go, and how much would it cost to clear the smell if the problem were not confined to just one spot?

Chris Coffin, production director at the Alexandria branch of the specialty cleaning firm ServiceMaster, offered some ballpark figures.

If the cat damaged the carpet and padding, Piergallini would most likely have had to pony up $300 to $400 to spot-clean the carpet with an enzyme treatment and replace the padding. If the subfloor was affected, fixing it would entail cutting out the damaged section or sealing the concrete, both of which would have added a few hundred dollars to the cost. The costs would have climbed if the home's hardwood floors were saturated or stained, he said. Replacing a floor is the only viable option if it is soaked so deeply that it can't be sanded.

But there's no guarantee of what the outcome will be at a set price, especially if the offending odor comes from cigarettes, Coffin said. "The amount of nicotine that comes oozing out of the walls is amazing. You may have to clean it three times. Our technicians hate those jobs because it seems like they never end."

After they scrub the walls, they typically coat them with a thick primer and then paint them to lock in residual odors. In some cases, insulation may need to be removed to get rid of the smell.

The options go on. There are airborne odor-removal methods, including ozone gas that binds with odor molecules and neutralizes them. ServiceMaster uses ozone chambers in its facilities to treat smelly, fire-damaged furniture. The furniture sits in the chamber for a few days with the gas circulating around it.