Definitely clean floor under carpet area to remove the smell. There are products on the market for this or you can clean with a vinegar/water solution. If you see black areas on the floor under the carpet that will indicate a buildup of old urine.

Years ago we had a couple of cats that didn't like our new baby. They started urinating right outside the litter box on the carpet. The time to sell came a few years later. Despite lots of cleanings there was still a faint cat urine odor when it was humid outside. It was on the OSB (or whatever it was). We pulled out the carpet, washed the area with Nature's Miracle (or something like that) sold in pet stores. We poured a lot of baking soda over the area and let it absorb any remaining odors. The final step was sealing it with Kilz. There might be better sealing choices, but it's what we had. The combination worked. No more smells on high humidity days.

If all of the above worked for cat urine, I'm pretty sure it would work for human waste stains and odors. One additional note: if you find stains, also check nearby baseboards. We had to remove a small section and clean there too.

Frank, never be embarrassed or shamed by the human condition. My husband had and died of dementia. Sometimes it's not just floors and subfloors damaged by incontinence.

I would start by spot treating with Nature's Miracle, replace the subfloor anywhere where messes soaked through or were especially bad, then Kilz the whole subfloor.

So I've only had carpet replaced/installed once in my life. Through Lowe's. For these comments about inspecting the subfloor, applying Killz, etc. ... Can I work with the installer company to make two visits? One to rip out the old floor-to-floor and one to install the new? Should the salesperson/estimator that comes out be familiar with this sort of situation and perhaps pull up some of the carpeting to inspect the subfloor to determine damage and recommend remediation before install, or are they pretty typically cookie-cutter rip-and-lay? I'm not particularly handy, but I can watch YouTube videos ... do I need to rip up sections of the carpet and handle the inspection and any pre-treatment of the subfloor myself?

TIA, David

You would be wise to rip up in small sections, remove and inspect subfloor. Most carpet installers rip out old and lay the new on all the dirt that is on the floor. I grabbed a ShopVac vacuum and cleaned the floor while they were getting the new rug in the house to install. Amazing how much dirt/sand collects on the floor under the carpet.