Do you know your blacklight UVA from your germicidal UVC?

When buying Ultraviolet (UV) lightbulbs, it’s important to know which type of bulb is the right one for your needs.

At Lightbulbs Direct, we sell three different types of UV bulb, and (here’s the important bit) one type is not suitable for all uses. A blacklight blue (BLB) bulb won’t help you kill flies, just as a germicidal UV tube won’t help you detect forged bank notes. Once you’re aware of the different types of UV lamp and what they should be used for, picking one will be a lot easier.

With that in mind, here’s everything you need to know to buy UV bulbs in confidence.

What is UV?

It is often referred to as ultraviolet ‘light,’ but UV is a type of electromagnetic radiation with wavelengths shorter than visible light and longer than X-rays.

Electromagnetic Spectrum

All electromagnetic waves are measured in metres, but some wavelengths (like UV) are so small that they’re measured in nanometres (nm). You will often see product descriptions on Lightbulbs Direct reference the ‘nm’ range of the lamp because it directly affects what type of bulb it is.

UV radiation falls into three categories depending on its wavelength: UVA, UVB and UVC. The shorter the wavelength, the more energetic the radiation, and the more harmful it can be. Shorter wavelength radiation, however, is less able to penetrate human skin. The sun gives off the most harmful UVC rays, but they are not strong enough to penetrate the earth’s atmosphere (luckily for us).

The chart below shows the respective wavelengths (in nm) that different types of UV lamps produce, and where they fall on the UV spectrum. The three different types of UV bulb available are Blacklight Blue (BLB), Blacklight (BL368), and Germicidal.

UV Spectrum

These are each meant for very different uses and, in the case of germicidal lights particularly, could be hazardous to your health if mixed up. With that in mind, we’ve put together a handy guide to help you determine which UV bulb is the right one for you.

Blacklight Blue (BLB)

These are the type of ‘glow-in-the-dark’ bulbs that most would associate with ultraviolet light. The wavelengths that these UV lamps emit are between 370–400nm, right on the border of visible light. Typical uses include:

  • Anti-theft protection
  • Nightclub lighting
  • Detecting forged bank notes
  • Carpet cleaning (to detect stains)
  • UV nail lamps
  • Scorpion detection!

BLB bulbs are covered by a very dark blue or purple filter, and give off a purplish glow. Fluorescent tubes – either straight or turned into more compact shapes, like the example pictured – are the most common type but there are other lamp varieties available.

When using BLB lamps with UV varnishes or paints, check the manufacturer’s guidelines on the correct lighting needed to activate their product.

While BLB bulbs are not hazardous to your health in the same way that germicidal UVC bulbs are, they should always be handled with care. Wear gloves when handling them to avoid contaminating the bulb, and ensure they are disposed of safely. Avoid long exposure where possible.

See here for some more advice on the safe handling and disposal of lightbulbs.

Blacklight (BL350/BL368)

Blacklight lamps are not to be confused with the blacklight blue type described above. While they still fall into the same UVA bracket on the ultraviolet spectrum, the slightly shorter wavelengths (between 350-370nm) result in very different effects. Common uses for these bulbs include:

  • Bug zappers (the UV light attracts bugs)
  • Suntanning
  • Polymerisation

They emit a mixture of ultraviolet and visible light and will appear to glow a luminous blue colour when operating.

Again, ensure these bulbs are handled and disposed of with care. Here’s that link again with more information about the safe handling and disposal of lightbulbs.


These lamps have the shortest UV wavelengths (between 200-280nm) and as a result are potentially the most harmful. Accordingly, extra care should be taken when handling and using these types of UV lights.

The type of UV radiation these bulbs emit targets the DNA of microorganisms, causing cell death or making reproduction impossible. They’re certainly not the type of bulbs to be used in the home. They’re mainly used in professional and industrial environments in processes such as:

  • Water treatment
  • Disinfection
  • Sterilisation
  • Food sanitation

Like blacklight UVA lamps, germicidal UVC lights are commonly sold as tubes, either straight or turned into more compact shapes. Unlike the UVA lamps, germicidal tubes are usually transparent.

Wear protective clothing when handling germicidal UVC lamps and keep them away from your skin and eyes. It is best to avoid prolonged exposure to the light when it is in operation.

If you’re still in doubt about what type of UV bulb you need, please contact us for more information.

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