Looking Fit 01/2004: wolff words: Measuring UV Output

Measuring UV Output

It’s January, and salons nationwide are gearing up for the busy season. Many salon operators finally have started using UV meters to monitor their tanning equipment and lamps. However, we frequently are asked what the lamp readings should be after 100 hours of usage. The following will answer that question and explain more about UV output.

A handheld UVB/UVA meter is an excellent tool to measure lamp output. This particular type of meter gives an indication of total UV output. While not as accurate as expensive precision testing gear, a handheld meter allows a salon owner to track decline in UV output over time in a narrow fashion.

It is important to understand that handheld meters are not accurate enough to compare different beds with each other or different lamps with each other. This is due to the spectral character of the tested product in relation to the sensitivity of the meter at specific wavelengths. Additionally, when trying to compare one set of bed/lamp data with another, users actually are looking at results from many variables other than lamps, such as bed geometry, lamp density, distance from lamps to tanner, acrylic solarization, etc.

Ideally, testing should be done after relamping the bed. Warm up the bed and lamps for 15 minutes, and always test at the same time of the day so variables such as heat buildup are as close as possible to the same conditions from test to test. Consider doing all testing after the first 15 minutes of each test day. Record zero-hour readings. Test again every 100 hours and compare to the zero-hour readings. When output declines by 25 percent to 30 percent, replace the lamps before customers begin to complain. Do not rely upon the lamp manufacturer’s life-expectancy claims.

To answer the above question—what to do when lamps have 100 hours of usage—use this as the zero-hour reading. As sunlamps typically decline faster during the first 100 hours than at any other time in their life, plan to relamp when a decline of 15 percent is detected.

UV exposure causes acrylics to degrade over time. The acrylic’s ability to allow UVB to pass diminishes more rapidly than passing UVA. Most acrylics transmit 94 percent to 96 percent of the UV when new, but as they age (2,000 to 5,000 hours) they will drop to lower effectiveness, with emphasis on reduced UVB output. This process is known as solarization.

To measure the degradation of acrylics, a UVB meter is better than one for UVB/UVA. Measure without the acrylic after relamping, then measure after reinstalling the acrylic. Be sure to measure at the same point(s) and at the same distance(s) from the lamps. The lower value divided by the higher value equals the approximate transmission percentage.

Replace acrylics when the transmission percentage is between 80 percent and 90 percent. Because sunlamps emit predominantly UVA, and acrylic solarization most significantly affects transmission of UVB, the UVB/UVA meter will not give accurate enough data to protect a salon owner’s business from “no tan” complaints due to acrylic solarization.