Why Does the Pet Smell Come Back After the Carpets Are Cleaned?

Quick answer: Pet accidents soak through to the pad, the slab and the baseboards, and carpet cleaning reaches only the fibers on top. When moisture returns, from the cleaning itself or a humid Austin afternoon, the residue underneath starts to smell again.

Why does the pet smell come back after a carpet cleaning?

In most homes, the smell comes back because the carpet was never the whole problem.

You know the pattern. The house smelled great for a day or two after the cleaners left. Then a muggy afternoon rolled in, the AC cycled on, and there it was: a faint pet smell in the living room, or a strong one in the corner where the dog used to sleep.

It isn't a mystery, and it usually isn't a sign the carpet cleaner did a bad job. It means the smell lives somewhere the cleaning wand never reaches.

Why can cleaning make the smell worse at first?

A pet smell is often stronger right after a carpet cleaning, for three reasons:

• Water wakes the odor back up. Old pet accidents dry into residue that sits quietly until it gets damp again. Hot water extraction adds moisture, and the smell rises with it.
• The cleaning reaches the fibers, not the pad. Carpet cleaning is built for the top of the carpet. A pet accident soaks straight through to the pad underneath, and sometimes into the floor below that.
• Drying takes longer than you think. In our humid months, a freshly cleaned carpet can stay damp underneath for a day or more, especially in a closed-up room.

Once everything dries, the smell usually settles back to where it was. The trouble is where it was.

Where does pet odor actually hide?

A pet smell that keeps coming back usually lives below or beside the carpet:

• The carpet pad. Pad is thick and spongy, and it holds whatever soaks into it. A spot that looks clean on top can still be soaked underneath.
• The slab. Most Central Texas homes sit on concrete slabs. Concrete is porous, and repeated accidents in the same spot soak into it. That odor rises again every time the floor picks up moisture.
• The tack strip and baseboards. The wood strips that hold the carpet in place, and the bottom edge of the baseboards and drywall, soak up odor in corners and along walls where dogs and cats like to mark.
• The subfloor in older homes. In a pier-and-beam home, the wood subfloor can hold odor the same way a slab does.
• Everything else that's soft. Couches, dog beds, curtains, rugs and the favorite blanket on the back of the chair.
• The HVAC system. Pet hair and dander collect at return grilles, in the filter and inside the ducts, and the system spreads the smell every time it runs.

Why does Austin humidity bring it back?

Old pet residue draws moisture out of the air, and damp residue smells stronger. On a dry day it stays quiet. On a sticky spring or summer day, when indoor humidity creeps above 55 percent, it picks up moisture and the smell returns.

That's why so many people tell us the smell "comes and goes." It follows the weather: worse after rain, worse when the AC is short-cycling, better in a dry cold snap. Keeping indoor humidity at 50 percent or below helps. Our Central Texas humidity guide walks through how to get there.

How do you find the real source?

Start with your nose and a flashlight, before you spend money on another cleaning:

1. Smell low. Get down near the floor along walls, in corners and near doors. Pet odor is usually strongest at floor level.
2. Use a UV flashlight at night. An inexpensive UV (blacklight) flashlight makes many old pet stains glow in a dark room. Mark each spot with painter's tape.
3. Check the pad in one bad spot. If you're comfortable doing it, wear gloves (tack strip is sharp), lift a corner of carpet near a marked spot and look at the pad and the concrete. Dark staining underneath tells you the odor has gone deep.
4. Smell the returns. Stand near your HVAC return grille when the system kicks on. If the smell is strong there, the system is spreading it.

What helps with a pet smell that keeps coming back?

Work from the bottom up, once you know where the smell lives:

1. Treat spots with an enzyme cleaner. Enzyme cleaners made for pet accidents break down the residue behind the smell. Use enough to reach as deep as the accident went, and let it dry fully.
2. Replace the pad in the worst areas. For heavy or repeated spots, cleaning isn't enough. Cutting out and replacing the pad is often the only real fix.
3. Seal the concrete or subfloor. After the pad is out, clean the slab and roll on an odor-blocking sealer or primer before new pad goes down.
4. Replace the tack strip and seal the baseboards in corners where pets have marked.
5. Wash every soft thing you can. Pet beds, blankets, throws and washable cushion covers, in hot water if the labels allow.
6. Change the HVAC filter and vacuum the return grilles. With pets, check the filter every month.
7. Clean the carpet last, once the sources underneath are handled.

Our guide to pets and indoor air has more everyday habits for keeping a pet-friendly home fresh.

Where does a whole-home treatment fit?

A whole-home treatment comes last, after the worst spots are fixed. A home that has had pets for years still carries odor on hard surfaces all over the house: baseboards, cabinet fronts, door frames, closet shelves, the inside of ducts. None of those ever see a carpet cleaner.

Our whole-home dry fog treatment reaches them. The patented VaPURE system floats a hydrogen peroxide and peracetic acid solution onto baseboards, door frames and closet shelves and through the HVAC ductwork without getting the couch or the dog bed wet, and then a surface protectant goes on. On treated hard, non-porous surfaces it helps control the growth of odor-causing microorganisms. It's done in one day, so the dog sleeps at home that night.

For stubborn pet odors, our Odor Treatment follows the dry fog with an ozone shock treatment while the home sits empty. People and pets stay out for up to 48 hours. It works best after the soaked pad and floors are taken care of, because no treatment can keep up with a source that's still there.

Common questions

Should I just replace the carpet?

Sometimes. If accidents have happened in many spots over many years, new carpet and pad, with the slab sealed underneath, may be the most realistic fix. If the problem is limited to a few areas, replacing the pad and sealing those spots is usually enough.

Will the smell come back after a whole-home treatment?

We don't promise that it won't. If a pet keeps having accidents, or a soaked spot is left in place, the odor will keep coming back. The treatment helps with the odor left behind once the sources are handled, and most homes smell noticeably fresher.

What do we do with the pets on treatment day?

Pets stay out with you. For a dry fog treatment, plan on a day out. For an Odor Treatment, plan for up to 48 hours with a friend, family or a boarding stay. Birds go with you either way. For a dry fog treatment, cover fish tanks and turn off the air pump; for an Odor Treatment, move them out.

Get a free phone consultation

Book a free phone consultation. A Comfort Advisor will call you, learn what's going on in your home and send a written quote based on square footage. Pure Maintenance Austin, brought to you by Gold Eagle Services, serves all of Central Texas, including College Station, Round Rock, Georgetown, San Marcos, Bastrop and Marble Falls.

Call 512-904-4646 or email IAQ@goldeagleservices.com. We're open Monday through Saturday, 7am to 7pm.