Why Doesn't My UV Black Light Make Pet Urine Glow?

UV black lights are used to spot old animal stains like dog or cat pee that aren't visible to the naked eye. Black light torches shine wavelengths that cause the proteins and phosphorus in pet urine to glow, exposing the cause of odours and concealed stains. The Odorex Pet Urine Stain Detectors has a specific wavelength for detecting animal pee and is safe to use without protective glasses (unlike the powerful lights you see on CSI TV programs).

If you've never used UV black lights to find pet pee, you could have some difficulty finding the stains you're looking for so here are some reasons you can't find the animal urine stains.

The Room Must Be Dark

Our model of UV works best when there is no ambient light. Wait until nightfall, turn off all of the lights in the room or area you are in and close the curtains and doors.

Keep It Charged (or Battery-Fresh)

Our current Pet Urine Stain Detector is USB-C rechargeable, with no batteries required — just make sure it's fully charged before first use, as a low charge will produce a weaker glow (approx. 5-6 hours of use per full charge). If you have one of our earlier battery-powered models (3 x AAA, approx. 50 hours of use), the same idea applies: fresh batteries give the brightest, most reliable glow, and it's worth removing them when the torch isn't in use for extended periods.

Different Things Will Glow Under Blacklight

Once the torch is turned on, hold it at arms length and shine at the floor just in front of your feet. Slowly move through the room and allow your eyes to adjust to the UV light. You may see other fluorescent specs glowing. Other compounds, like carpet cleaner or a drink that has been spilt, frequently emit a dazzling white glow. Pet urine fluoresces to a light yellow so that is what you should look for. Checking your pet's skin rather than your floors? Ringworm (a fungal skin infection) also fluoresces under UV light — typically a bright yellow-green glow concentrated on the fur or skin itself, which looks different from the duller, more diffuse glow of dried urine on carpet or fabric. Consider that the smell might not be coming from where you think it is so conduct a thorough search. Commonly dogs will pee near outdoor access doors, under or behind furniture if an accident or up against tables, beds etc if marking. Typically cats are sneakier and prefer to pee around the back of couches, up against walls and curtains, in closets that have been left open, or piles of clothes etc.

Surfaces Must be Dry

Dry pet urine is the only type of urine that UV black lights can detect. The glow it creates will be weak or nonexistent if the pee is still wet or not completely dried. Even if the stain has had time to set, moisture on the stained surface or humidity in the air (such as that found in the bathroom, kitchen, or outdoors) may reduce the black light's effectiveness. Allow the pet pee to completely dry before attempting to identify it with your UV light for the brightest glow.

Bear in mind that pee on extremely absorbent textiles can sometimes penetrated deeply, past the surface layers. If so, there might not be enough urine on the surface to cause a noticeable glow.

Surfaces Can React Differently Under UV Light

In general, surfaces like carpet or upholstery will respond to UV light better than tile, hardwood floors, and other hard surfaces. A stronger glow can be produced since pet urine has a higher propensity to dry in greater quantities on porous absorbent surfaces. With hard surfaces, the pee typically dries in a thinner layer that is simple to remove with cleaning solutions or wear and tear. In other words, the glow gets brighter the more urine there is.

Darker hues absorb more light so it may be difficult for your black light to display a brilliant glow on dark surfaces - the glow will be lighter the darker the surface. For instance, a tan couch will be easier to spot stains on than a brown one.

Another issue is patterns. If the surface is patterned, the glow can become less noticeable since it will blend in with the pattern. A surface with a consistent colour will perform best with your UV light.

Still Can't Find the Pee Stains?

Make sure your UV black light is functioning properly by performing this fast test. Grab some white paper, then hold it up to your black light. You should see a strong, clear glow — blue if you have our newest 365nm black mirror filter model, or violet/purple if you have an earlier 385-395nm model. If your light's intensity is low it may be defective, so please get in touch with us so we can replace it.