How do I find old dog pee spots in my house?

Use your nose to sniff out soiled areas. Examine the suspect area closely to catch hard-to-find soiling. If you have a black light, use it to identify soiled areas and lightly outline the areas with chalk.

Why Does My House Smell Like Dog Pee? Finding the Source

This guide covers how to track down a dog urine smell in your home: finding hidden and old spots with your nose, a black light and chalk, the places the sources name, urine that has soaked below the surface, and what to do once you find it, using what Humane World for Animals, the AKC, the IICRC and the Carpet and Rug Institute (CRI) say.

Why you can smell it but not see it

The AKC says: "Your dog isn't always going to pee in front of you. Your dog also could've had an accident in another room or when you're not home without you realizing." Humane World for Animals adds: "In some cases, old messes will have dried invisibly and be hard to locate."

The IICRC's carpet tip sheet describes a slow reaction between urine and carpet dyes:

"The other type of reaction develops slowly over several days or months and can result in permanent changes to the dyes and fiber. In many cases, this type of damage can only be seen with the aid of a black/UV light."

"The decomposing urine can also produce an objectionable odor."

Sources: AKC, How to Get Rid of Dog Pee Stains and Smells; Humane World for Animals, How to Remove Pet Stains and Odors; IICRC Consumer Floor and Furnishings Care Information (PDF).

Step 1: Use your nose and eyes

Humane World for Animals lists these steps to find older messes:

"Use your nose to sniff out soiled areas."

"Examine the suspect area closely to catch hard-to-find soiling."

The AKC says:

"Sometimes dogs will pee in more secluded or hidden parts of the home, so it may not always be easy to locate where your dog peed if you didn't see them do it. But oftentimes, you'll be able to smell it, even if you don't see it."

Sources: Humane World for Animals; AKC.

Step 2: Check with a black light and mark with chalk

Humane World for Animals says: "If you have a black light, use it to identify soiled areas and lightly outline the areas with chalk." A pet stain tip sheet on the Pendleton County, Kentucky, government site says: "A blacklight bulb will usually show even old urine stains." It adds: "Turn out all lights in the room, use the black light to identify soiled areas, and lightly outline the areas with chalk."

The AKC describes urine stain detectors:

"Urine stain detectors help identify spots where your dog has peed, even if they're not wet anymore. Most use LED UV light to detect urine stains on different surfaces, allowing you to clean more efficiently."

The IICRC says: "Cleaning professionals use a black/UV light to identify all areas that have urine that can't be seen with the naked eye. Not all urine stains show, so this is the proper way to identify affected areas." On what you see after cleaning, the IICRC says: "If the area still fluoresces after professional cleaning, it does not mean the service provider did an incomplete job removing the urine."

For a step-by-step walkthrough, see how to find pet urine with a black light on petcleanupkit.com.

Sources: Humane World for Animals; Pendleton County, KY, Removing Pet Stains and Odors (PDF); AKC; IICRC tip sheet.

Where to look

These are the places the sources name:

Carpet, drapes and upholstery. The IICRC says: "Dogs and cats may be our best friends, but they contribute to many issues when it comes to carpeting, draperies, and upholstery."
Dog beds and crate liners. The AKC says: "Fabric items like dog beds or crate liners can often be washed with hot water and detergent."
Wood, walls and baseboards. Humane World for Animals says: "If the wood on your furniture, walls, baseboard or floor is discolored, the varnish or paint has reacted to the acid in the urine."
Secluded spots. See the AKC line above on "more secluded or hidden parts of the home".

Sources: IICRC tip sheet; AKC; Humane World for Animals.

Urine that has soaked below the surface

The AKC's answer to "Why does my house still smell after cleaning dog urine?" is:

"Urine may have soaked into padding, upholstery, or wood. Repeated treatments or professional cleaning may be necessary."

Humane World for Animals says: "Your job will be more difficult if urine has soaked down into the padding underneath your carpet. In some cases, you may need to replace portions of carpet and padding." On floors, the AKC says: "Urine can penetrate hardwood, making odor removal more challenging."

See our guide to pet urine in carpet padding.

Sources: AKC; Humane World for Animals.

Why it can smell stronger on humid days

The IICRC tip sheet quotes its S100 carpet cleaning standard:

"Elevated heat and humidity created from the cleaning process can amplify odors, so they are more evident during and after cleaning and during warm, humid conditions."

On cleaning urine spots, the CRI says: "Don't use a steam cleaner when dealing with urine spots because the heat will set the stain and the smell."

Sources: IICRC tip sheet; CRI, Cleaning and Maintenance.

Cleaning the spots once you find them

We cover each surface in a separate guide:

Old, dried or black-light spots: How to Get Old, Dried Pet Urine Stains Out
Rugs: How to Get Dog Pee Out of an Area Rug
Sofas and chairs: How to Get Dog Pee Smell Out of a Couch
Laminate and vinyl plank: How to Clean Pet Urine From Laminate and Vinyl Plank Floors
Tile and grout: How to Clean Dog Pee From Tile and Grout
Dog beds: How to Clean a Pet Bed After an Accident

For wall-to-wall carpet, see how to get pet urine smell out of carpet on petcleanupkit.com. Whatever you use, the CRI says "you should still pretest any cleaner on a scrap of carpet or in an out-of-the-way area of your carpet."

Clean every spot you find. The AKC says: "Lingering scent can draw your dog back to the same area, reinforcing accidents." See also why dogs and cats keep peeing in the same spot.

Sources: CRI, Cleaning and Maintenance; AKC.

When the smell may not be the dog's urine

The IICRC's S100 standard, as quoted in its tip sheet, says:

"Odors can occur from sources other than bodily discharges (e.g., hair, dander, and body oils from dogs and cats)."

"Mold and mildew odors perceived to be coming from the carpet can actually also be present in other absorbent items in the home such as furniture, baseboards, drywall, window coverings, bedding as well as the HVAC system."

On a musty smell, the tip sheet says it is "best to eliminate it at the source" and that "you should always consult with an IICRC-Certified Mold Remediation Specialist".

Source: IICRC tip sheet.

When to call a professional

The AKC says:

"If odors linger despite repeated cleaning, or if there are multiple or deep stains, professional cleaning may be the best option. This is especially useful for carpets, upholstery, and car interiors."

The CRI says: "If necessary, call in a certified carpet cleaning firm that knows how to remove pet stains and odors permanently."

Sources: AKC; CRI, Cleaning and Maintenance.

About your dog

This guide is about finding the smell. On repeat accidents, Humane World for Animals says: "If your pet is having regular accidents, have them checked by a veterinarian to rule out medical causes."

Source: Humane World for Animals.

Using P-Cleaner

P-Cleaner is the Pet Stain & Odor Eliminator Foaming Liquid from Pet Cleanup Kit. The product listing says: "Our rinse-free, water-based formula tackles the toughest stains and odors from urine, feces, vomit, and other organic messes on carpets, rugs, upholstery, and hard surfaces." It also says: "Works on carpets, upholstery, tile, and more.", "No scrubbing necessary" and "Odor-Free & Residue-Free". Test it on a hidden spot first, as the CRI advises above. Follow the directions on the product label.

Still hunting for spots? The full kit includes a black light.

Buy P-Cleaner on petcleanupkit.com

Quoted from the petcleanupkit.com product listing.