Probably the most popular size of germicidal bulb is the G30T8.  It's used in many types of area where killing germs in the air is becoming more and more of an issue. That's why there are germicidal fluorescents for every need.  Because of their size and their effectiveness, you'll find these bulbs in service in places like hospitals, clinics, food handling business and restaurants.  The G30T8 light bulb is a 3 foot version and is the largest of the fluorescent type so it has many large facility uses.  This is especially true for USDA facilities or food or anywhere there is a need to keep germs in the air at a minimum, then you'll find germicidal lamps in use.  There are several types that you might be familiar with as far as size goes.  The G8T5 germicidal is 12 inches, the G15T8 is 18 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 virtually the same, but some people might prefer one over the other. 

As with all fluorescent bulbs, they rely on ballasts inside of the fixtures in order to make them work. Ballasts are available from Universal, Osram Sylvania, among others. Almost all fixtures for these bulbs come with ballasts already mounted and wired. 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 G30T8 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.  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, USDA food service buildings across the country, we make G30T8 germicidal a perennial offering. There will never be a time when these will not be used in applications for killing bacteria, in fact, the applications seem to be increasing. Remember, there are many types of germicidal lighting, we have the G30T8 as the most common one 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.