Though personal observation of local properties and via customers requests for help on the OdorXit help line, we have seen and/or heard about flooring that was heavily contaminated with urea salt. Some were just stained black, while others, after being repeatedly washed with a variety of detergents and completely dried, would become wet and sticky again after a few hours from the hygroscopic action of the remaining urea salt. Now, we are talking about really contaminated flooring!
Though these extreme cases are more or less rare, more aggressive treatment was indicated.
More aggressive treatment in one case included sanding the surface of the area that was black and drilling a series of small holes through the hardwood flooring. The combination of the two removed the floor's finish and the holes provided a path for OdorXit to get to and neutralize the urea that had soaked into the surface and ran between and under the floor boards.
In another case more aggressive treatment included removing the most heavily contaminated part of the flooring. This revealed that the rafters and ceiling below the removed flooring was also heavily contaminated. Treating these newly exposed areas with OdorXit finally eliminated the odor problem.