There are two actions I am going to discuss briefly, involved in dog urine cleaning. One is the action of actually extracting (removing) the urine. The other action is a chemical action or reaction that happens when the correct chemicals come in contact with the urine or urine residue. The process of removing the urine can be done with extraction (vacuuming it up or out) or absorption (absorbing it into a cloth or paper towel etc.). If you add a little water to this step as you do it you will get a rinsing action that helps clean more of the dog urine out. It is always more effective when you include this process of removing as much dog urine residue as possible first. Then apply the chemicals that will create a molecular change and go to work on the remainder of the residue still left in the your carpet or mattress for example. These chemicals, and there are several type that work, need to contact the urine residue to work on it and change it. Molecule for molecule exchange it is called by some. Or other chemicals that digest the residue. If you are cleaning tile, hardwood, vinyl etc. it is much easier and quicker to extract or absorb and be able to remove almost all of the dog urine. But if you are cleaning carpet, upholstery, a mattress or another absorbent surface you will want to consider including the extraction step. Not all chemical dealers include this step in their instructions or recommendation. Some will say just apply the chemical and let it do the job. This will work but it is much more successful on light urine contamination. To summerize you can remove urine with only a chemical reaction. Depending on your situation you may need to use a combination of both actions for your dog urine cleaning. If you use only chemicals on a heavy urine spot you will have to soak the spot thoroughly and it is then a good idea to remove the chemicals. So you are back to extracting or absorbing to remove the excess chemical residue. On a light contamination situation you do not need to soak the area as heavy and the chemicals will evaporate. This way you can accomplish the results without extraction. Although with some products you will find a sticky chemical residue left behind.