One of the more common sizes of germicidal bulb is the G15T8.  It's a shorter size and can be used in places where a smaller light fixture is needed to kill germs in the air.  Because of their size and their ability to kill bacteria, you'll find these bulbs used in places like health care facilities, clinics, food handling business and restaurants.    This is especially true for USDA facilities or anywhere there is a need to keep germs in the air at a minimum, then you'll find germicidal lamps in use.  The G15T8 light bulb is a 18 inch version and is the medium length among the various choices.  There are several other types that you might be familiar with as far as length goes.  The G8T5 germicidal is 12 inches, and the G30T8 is 36 inches and would be used as the product was specified.  We supply these lamps in both Sylvania and the Philips version.  They are the same, but some people might favor one brand over the other. 

As with all fluorescent bulbs, germicidal bulbs rely on ballasts inside of the fixtures in order to make them work. Ballasts are available from Universal, Osram Sylvania, among others.  The ballast is important because it is specific for each type of lamp.  You can't change from one type of fluorescent to another without changing the ballast in most cases.  Most of the time the ballast and the lamp are matched electrically and so it's good to make sure the ballast you have is the right one for the lamp you choose. The G15T8 germicidal fluorescent light bulbs typically operate on a magnetic ballast which is less efficient than it's electronic counterpart, but that's beginning to change.  It's operates off the same ballast that an F15T8 does, but that doesn't mean it should be used in that fixture.  Look for this lamp commonly used in a shielded fixture out of the way of anyone's field of view.  The reason for that is that germicidal light bulbs can cause eye damage, that's why they're always used in an indirect lighting fixture. In fact, here's a warning from the manufacturers.

Direct/Reflected exposure of the ultraviolet energy from this lamp to eyes/skin should be avoided to prevent serious burns. Protection should be provided by clothing, gloves, opaque materials, & ordinary window glass. Do not use for general lighting.

Because it's still very pervasive in many health facilities, hospitals, USDA food service buildings across the country, we make G15T8 germicidal available. There will never be a time when these will not be used in applications for killing bacteria, in fact, the applications only seem to be increasing. Remember, there are many types of germicidal lighting, we have the G15T8 as one of the most common lengths used in lighting today. If you need help identifying one of these germicidal light bulbs, our customer service representatives can help you determine what you have.