What is the Difference Between Narrowband and Broadband UVB Lights?

Ultraviolet UVB bulbs are used in a variety of medical, industrial, and other applications. There are a couple variations of UVB bulbs, based on the output spectrum of the lamp.

These are referred to as Narrowband and Broadband UVB lamps. The names are somewhat self-explanatory in terms of the relative size of the output spectrum of each type.

The key differences between Narrowband (NB-UVB) and Broadband (BB-UVB) ultraviolet bulbs lie in their wavelength ranges, efficiency, and safety profiles, which determine their best applications.

Here is a breakdown of the key features of each, and the primary applications.

Wavelength Range

Narrowband UVB (NB-UVB) lamps emit a tight peak of ultraviolet radiation around 311–313 nm. This minimizes harmful shorter wavelengths below 300 nm that are more damaging to human skin and eyes.

Broadband UVB (BB-UVB) lamps emit a wider range (280–320 nm), including shorter, more damaging UVB wavelengths (290–300 nm). They are used more in applications where human exposure is minimized or entirely absent.

Key Differences

Medical efficacy. Narrowband lamps are generally more effective for skin treatments, as they have a higher therapeutic index. Broadband lamps are less efficient, resulting in a higher risk of burns when used to treat skin conditions on people.

Safety. The narrowband UVB bulbs have a lower risk of erythema (sunburn) and DNA damage, where broadband lamps have a higher risk of burns and skin damage due to the presence of smaller wavelengths.

Energy Use. Narrowband lamps are more efficient (less energy wasted) in general, with higher UV output at the desired wavelength for the same input wattage. Broadband bulbs are less efficient due to the wider spectrum.

Cost. While there are exceptions, the biggest drawback of narrowband UVB lamps is the higher price. They are a newer technology and the phosphors used to manufacture them are more expensive. This makes broadband UVB lights cheaper on average.

Narrowband UVB (NB-UVB) Applications

• Psoriasis (gold standard treatment, reduces scaling andinflammation)
• Vitiligo (stimulates melanocyte repigmentation)
• Eczema and Atopic Dermatitis (reduces itching and flares)
• Cutaneous T-cell Lymphoma (a type of skin cancer treated with UVB)

These lamps are also used for reptile lighting. Some high-end reptile bulbs use narrowband UVB light sources for safer, more controlled exposure.

Tanning bed lamps typically use a combination of UVA and some narrowband UVB to simulate sunlight.

Broadband UVB (BB-UVB) Applications

However, research and industrial testing are important applications. The broadband UVB wavelength simulates natural sunlight for material degradation studies (for example, plastics and coatings).

Lamps with a strong emission in the UVB range are also used in ultraviolet curing applications.

Rarely, vintage tanning bed systems used broadband UVB lamps, but modern ones avoid it due to the risks of skin damage. Modern tanning bed bulbs limit UVB output and use a combination of UVA and UVB, with most output in the UVA range.

Finally, the usage of broadband UVB has been studied in germicidal applications, specifically inhibiting photoreactivation of microbes. This is not a very widespread application, but interest in germicidal lighting has grown since COVID.

Which One is Better?

Whether narrowband or broadband lamps are better highly depends on the application. As with most lighting applications, there is no "one size fits all" solution.

For medical uses on humans, narrowband UVB is preferred. These bulbs are more effective, safer, and can result in fewer side effects when used as directed.

For reptiles, the right type of UVB lamp depends on a variety of factors, including the species of reptile. Some benefit from the more focused wavelength of narrowband UVB, while others need a broader spectrum for optimal health.

For industrial testing and research, broadband UVB may be used to expose materials to a fuller range of UVB. This is designed to mimic the natural degradation of materials under sunlight. Additionally, broadband UVB lamps are more common in UV curing equipment.

Safety Note

Both types of UVB lamps can cause skin damage if misused, although narrowband UVB is generally safer for prolonged exposure. Always consult exposure guidelines when using any ultraviolet light bulb, and consider the advice and recommendations of medical professionals.