We’ve previously talked about the importance of using UV meters to ensure optimal lamp performance; here is a related question: “I’m using a hand-held UV meter to register and track the output and service life of my lamps. The lamps installed in my 15-minute beds are registering about the same as different lamps I’m using in my 20-minute beds. Why is this?”
Before tanning equipment manufacturers market their products, they must test them with sophisticated spectroradiometry devices and determine the maximum exposure schedule (session times) in accordance with the regulations from FDA’s Center for Devices and Radiological Health. The maximum exposure is the amount of time that allows a tanner to receive four (4) MED (Minimum Erythemal Dose). Regardless of the number of lamps in the unit, the character of the unit’s original lamps, or the unit’s design, four MED is the maximum UV exposure allowed.
If you have questions, please email sales@wolffsys.com or call 800.959.6533.
The meter you are using is an excellent tool for tracking the UV output of a given set of lamps in a given sunbed. When you try to compare one set of bed/lamp data with another, you are actually looking at results from many variables other than lamps, such as bed geometry, lamp density, the distance from the lamps to tanner, acrylic solarization (transmissive quality), etc.
Remember, also, that commercial sunlamps emit almost all of their UV energy in the UVA region of the spectrum – maybe 96 percent of the energy is UVA, while only four percent is UVB. To make a lamp that will perform for shorter exposure times (a “hotter” lamp), lamp-makers generally add more UVB-generating phosphor. If all other things are equal, to produce a lamp with a 25 percent shorter maximum exposure (20 minutes vs. 15 minutes = 25%), only the lamp’s UVB emission needs to change by a small amount. The result might only be that the “hotter” lamp delivers 95 percent UVA and five percent UVB.
Since most of the energy from both of these lamp styles is UVA, your UV meter will give you very similar readings. After all, the meter is designed to detect total UV. There are other devices that actually “weigh” the erythemal effectiveness of the output tested, which would tell you something about maximum exposure times.
The spectral character of different lamps can affect any radiometer readings; this is another reason to avoid making comparisons between different lamps and tanning units. Without changing effectiveness, one lamp might have higher levels of irradiance at wavelengths not well-detected, while another lamp emits UV mostly at wavelengths easily detected by the radiometer.
