Does a sunlamp depreciate over time or just with use? Do lamps have a “shelf life?”
First, let’s talk about how a low-pressure sunlamp works. There is a thin phosphor coating on the inside of the lamp and a small amount of inert gas and mercury in the tube. When power is applied to the lamp, emissive material (a chemical coating) sputters from the cathodes at each end inside the lamp. These emissions assist in the ignition of an electric arc between the cathodes at opposite ends. The mercury vaporizes as a result of the arc, contributing its properties to the arc stream. The phosphors are “excited” by the ultraviolet energy of the mercury, causing them to fluoresce (shine).
As you can see, a sunlamp is composed of glass, metals, gas and phosphors. When Team Wolff System speaks about lamp performance depreciation, we are referring to the known characteristics of the phosphor contained within the sealed glass tube that makes up the lamp.
When a lamp is started and while it is operating, the depreciation process begins. The phosphor will weaken as the lamp continues to operate, producing less UV output. This is a natural result of the interaction between the phosphor material and the electric arc from one end of the lamp to the other, in addition to the phosphor-weakening factor of heat. This natural decline in output (from the degradation of the phosphor’s efficacy) leads us to the service life ratings we publish – service life equals the point where output has declined 30% from when the lamp was new.
Once the lamp is turned off, the depreciation process is halted until the next time the lamp is started. There is nothing organic in a lamp that will fail or spoil over time, as happens with bread or milk. Wolff’s service life ratings speak to lamp-on hours, not elapsed time. In some salons, it may take ten years to collect 1,000 hours on a lamp, whereas a busy facility may do that in a few months. If you burn a lamp for one hour then turn it off, put it in a time capsule, and unearth it 100 years later, it still has only one hour of use and is the same as when it was put away.
Therefore, tanning lamps sitting in inventory have no shelf life because the components used in the manufacturing process do not expire, age, deteriorate or spoil. The production date codes simply identify when the lamp was produced and are only used as a reference by the manufacturer to comply with FDA regulations, and at Wolff, as a component of our Quality Control processes.
Also, it doesn’t matter if the lamps are stored in a vertical or horizontal position. If stored vertically, be sure they are secure and will not be knocked over. Another question is, “Can lamps be stored in a cold garage?” This is not a problem; however it may take the lamps a few minutes to adjust to the change in ambient temperature and to light up fully in a tanning unit. Once it has adjusted, it’ll work fine.
