Hi, Louis. Pet stores have an enzyme solution that will destroy pet odors. There are many of these on the market and they all seem to work about the same. Let the floor dry well after you use it. As you know, it's not a good idea to get chip board or flake board wet since it expands and does not return to shape but you should be OK if you just get the board damp for a little while. If the board already has a misshapen surface, you should replace the board. This should be pretty easy to do. If there does not seem to be that much odor after you remove the carpet and pad, you might choose to forgo this step.
After the enzyme solution is dry, paint on a coat or 2 of Zinnser's B-I-N. This is nothing more than shellac with a white pigment in it to show you where you have applied it. Shellac is great for sealing odors in wood. Since the solvent for shellac is alcohol, it will smell like crazy while you are applying it. With a couple of windows open, the smell will dissapate as it quickly dries. However, since the alcohol is flammable, you want to remove any sources of ignition in the area. This includes things like furnace, waterheater and stove pilot lights and electric fans or other motors. You can apply this to a floor with a roller on a pole easily and it will save your back. Don't forget to get some extra denatured alcohol for clean-up.