Color temperature of lights - demo (C) D Friedman UV light, Woods Lamp
Buy & Use for building investigations of animals, materials odors, urine, blood, other contaminants

  • BLACK LIGHT & UV LIGHT USES - CONTENTS: Catalog of materials that can be observed, identified, or that will flouresce under UV light; How to use a black light (ultraviolet lights, bulbs, flashlights) or UV light also known as a Wood's Light, to track down the location urine and other animal indoor contaminants.
  • POST a QUESTION or READ FAQs about how to use black light or UV light or a Woods lamp in building investigations

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How to use a black light or UV light:

This article describes uses of UV light in building investigations. We describe the use of a black light, UV light to screen buildings for pet urine or urine from humans or other animals even where no stains are visible in or around buildings.

We provide a catalog of materials that glow or flouresce under UV light and cite scholarly-research for many of those materials and the forensic use of black light.

We also use UV light to screen buildings for other body fluids, including blood. Small black lights are available from pet supply stores, art supply stores, and forensic and police equipment suppliers and are generally inexpensive.

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Guide to Using Ultra Violet Light (UV light or "black light") for Forensic Building Investigations

One of the most effective uses of UV light in building investigations is the tracking down of odors & contaminants such as urine, urine stains, or odors & allergens from pets, rodents, or other animals, even human.

But because a large number of materials will fluoresce under a black light, we need to give some thought to how to interpret what our UV light is actually revealing when we shine it on a building material or surface.

Discussed here: Catalog of materials that fluoresce under black light (UV light) & sources of UV lights, supplies. Using a black light to find sources of indoor building smells and odors from dogs, cats, rodents, bats, unusual pets, and even people can be tricky; here are our suggestions.

Article Contents

Watch out: While in our OPINION the ordinary use of UV flashlights and UV lamps for purposes of building or environmental inspection or security screening constitutes no unusual health risk, excessive or inappropriate exposure to high levels or protracted durations of ultraviolet light may be unsafe and possibly carcinogenic.

A much cited study indicated that "The risk was not significantly or consistently raised for exposure to fluorescent lights at home or at work."[12]

Question: using a black light to track down iridescent powder substance in carpet

direct lighting hides problematic light colored mold colony on this wainscot paneling

Can you be of help identifying a carpet (?) problem I am having in my apartment?

I discovered this as I was using a black light to look at some iridescent fishing lures the other evening. I noticed several yellowish glowing spots in the bedroom carpeting. This caused me to check the living room and dining area carpeting, where I found the same type yellowish glowing areas.

The areas are ‘dusty’ in appearance and appear in a variety of patterns. I further checked the baseboards, some less trafficked areas behind the bed and other furniture, and the furniture and counter surfaces and found the same yellowish areas.

It quickly returns after cleanup. These areas do not appear in normal daylight, but do appear under a black light. Of course, the iridescence is greater at night when I can darken the apartment, but it can be seen under the black light during the day. It should also be noted that my feet and toe nails show the same yellowish glow. I walk around bare footed in my apartment.

Bathing removes the powdery substance from my feet and my physician says I have no mold or other infection in my feet. It should also be noted that when I purchased my black light over a year ago, for fun I checked out my apartment and carpeting for mold, pet urine, etc. and found none.

I will be checking with a local 'home' inspection type company next week regarding this.

Thanks for you help, - J.N. 07/21/2012

Reply: What materials glow under UV lighting & what is a "black light"?

Black light bulb (C) Daniel Friedman

A competent onsite inspection by an expert usually finds additional clues that help accurately diagnose a problem concerning building contaminants or conditions. That said, there are a number of materials that will fluoresce under an ultraviolet UV or "black light", even clean white sheets appear to do so.

At above left we illustrate our darkroom test set-up for light source comparisons, in this case with a "blacklight" or UV ultraviolet light bulb (Woods lamp) installed in our test fixture using a 13W bulb produced by Feit Electric (photo at left).[5]

You may have spotted pet urine stains and pet urine-contaminated dust from carpeting, or insect fragments, or possibly some urea-containing materials.

The observation that many materials contain fluorescent molecules means that interpreting light or presumed stain patterns needs to be done with some sense of location, age, material, and context.

Definition of Fluorescence & UV lights or black lights - the Woods Lamp

We should explain the mechanism of fluorescence before listing things that fluoresce under black light or really UV light: According to a nice Q&A by the U. Illinois physics department, although infra-red and ultraviolet spectrums or frequencies are beyond what the human eye can see (some animals can see in these light frequency ranges),

Some materials have the special property that they absorb ultra-violet light and then re-emit the light at lower frequencies that our eyes can see. This is called "fluorescence. [3]

The actual wavelength of black lights or UV bulbs that operates in the UV range is 280-410nm usually narrowed to 368-371 nm wavelength light.

Because UV flashlights or bulbs may also emit some energy in the wavelength range that is visible to humans, when you plug in a lamp that contains a "black light" bulb, it won't appear to emit zero "light" (that you can see), but it emits so little light in the range visible to humans that these bulbs are popularly called "black lights".

Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation. It is a form of luminescence. In most cases, the emitted light has a longer wavelength, and therefore lower energy, than the absorbed radiation.

The most striking example of fluorescence occurs when the absorbed radiation is in the ultraviolet region of the spectrum, and thus invisible to the human eye, while the emitted light is in the visible region, which gives the fluorescent substance a distinct color that can only be seen when exposed to UV light.

Fluorescent materials cease to glow immediately when the radiation source stops, unlike phosphorescence, where it continues to emit light for some time after. Fluorescence has many practical applications, including mineralogy, gemology, medicine, chemical sensors (fluorescence spectroscopy), fluorescent labelling, dyes, biological detectors, cosmic-ray detection, and, most commonly, fluorescent lamps.

Fluorescence also occurs frequently in nature in some minerals and in various biological states in many branches of the animal kingdom. - Jstor, retrieved 2017/11/07, original source:

The term flourescence originated with Stokes (1853)

How to Use UV Lights for Surface Inspection

We have had a number of discussions with forensic investigators and building inspectors, have tested several UV light devices, and have experimented with the forensic use of UV light in our lab and in the field. And of course there are numerous expert sources for this topic.

In general inspectors find that you can use a good quality ultraviolet light source even in daylight (notice the use of small UV flashlights for document checks in airport security screening procedures).

But for weak or dilute sources of fluorescent materials, such as very dilute fluorescein septic dye that might appear in a waterway up to a week after a septic loading and dye test, screening the target using ultraviolet lighting under low light or dark conditions is still more effective.

Catalog of Materials & Products that "glow" or fluoresce under Ultra Violet Light - UV light, Black Light

Cat in the house (C) Daniel Friedman

Here is an alphabetical list of examples of fluorescing materials you might commonly see during an investigation inside or around a building. In parentheses our c=XX note indicates common colors you will see from each material when it is exposed to ultra violet light in a dark area.

Use a UV flashlight, a "black light" bulb in a portable light fixture, or similar equipment to screen for these or other fluorescing substances in and around buildings.

Faux UV does not show urine on cotton (C) Daniel Friedman

Research & Resources on UV Flourescent Light Uses

UV light or black light information, sources, suppliers

Watch out: "blacklight bulbs" that resemble incandescent light bulbs with a purple-colored exterior coating are sold as "black lights" but do not emit UV and cannot be used for forensic purposes. Those bulbs simply emit a dark purple light.


Continue reading at BLOOD in ART WORKS, TESTING FOR or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.

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