A salon operator recently asked this question of Team Wolff:
I have two 15-minute beds in my salon and tanners like them both. One is equipped with regular,100W lamps and the other has 100W reflector lamps. Readings with my UVA+B meter shows a pretty big difference between the two beds, with the reflector unit readings being higher. How can they both be 15-minute beds?
[gap height=”15″]
Remember, the maximum exposure time listed on your sunbed’s label refers to the time it takes to deliver four (4) MED – the maximum exposure allowed under FDA regulations. The exposure time is the result of testing the tanning system against its erythemal (burning) effectiveness. The sunbed manufacturer tests the lamp output at locations within the bed that approximate the tanner’s body position during use. Your UVA+B radiometer is testing total output (irradiance), which is mostly UVA. There are other affordable devices that can give you a better idea about the erythemal effectiveness which dictates the unit’s maximum exposure time, though they may not tell you as much about the output maintenance of your lamps.
[gap height=”15″]
Chances are, your two beds are not identical. There are probably differences in bed geometry, lamp density, lamp-to-tanner distance and other influential variables aside from the differences between a reflector lamp and a non-reflector lamp. The UVA+B meter is best for monitoring total lamp output, not comparing different lamps or systems.
[gap height=”15″][gap height=”15″]
Your reflector lamp system shows higher total UV, and the non-reflector lamp system is more erythemally effective.
[gap height=”15″][gap height=”15″]
The non-reflector lamp operates with a specular (like a mirror) reflector located behind the lamps (away from the tanner) which redirects the UV radiating from the rear of the lamp back toward the tanner. If non-reflector lamps are too close together, the efficiency of this specular reflector is actually diminished, as some of the UV energy is blocked by the lamps themselves.
[gap height=”15″]
Reflector lamps do not radiate from the rear due to the reflective coating inside and on the rear of the lamp. The specular reflector in the bed does not have much, if any, work to do. In fact, using reflector lamps would allow the bed-maker to eliminate the bed’s reflector without significantly affecting the system efficiency. If both lamp styles employ the identical phosphor blend, they will produce the same UV output. The reflector lamp, by itself, is more efficient, at delivery of the output, by 10-20% than the non-reflector lamp employed with an external reflector. This is due to:
[gap height=”15″]
- The inherent efficiency of an internal (to the lamp) reflector versus external,
- Short-wavelength UV loses potency over distance, particularly in the UVB region. It is simply further from the rear of the non-reflector lamp to the external reflector, then back to the tanner, than it is from a reflector lamp without the detour.
[gap height=”15″]
Of course, the sunbed manufacturer must take advantage of the reflector efficiency, whether internal to the lamp or external. Equipment with reflector lamps often has greater lamp density (closer together) than a bed equipped with non-reflector lamps. It is probably safe to assume that your “15-minute” non-reflector lamps employ a phosphor that is a bit more erythemally effective than that employed with your reflector lamps. This will account for similar exposure times from dissimilar systems. Your reflector lamp system shows higher total UV, and the non-reflector lamp system is more erythemally effective.
[gap height=”15″][gap height=”15″]
