One of the most important tasks of lighting in a modern building is to help people find their way out of a building when there is a fire or an emergency.  That's where exits along with emergency illumination become a critical working item.  They must simply be working at all times, not so building owners won't get cited for faulty equipment, but for helping people escape.  There are many types of exit sign light bulbs on the market because so many sign companies have used various product in the past. There are several general categories of sign bulbs which include incandescent, fluorescent, self luminous and LED sources.  For most people that are constructing a new building, the LED or light emitting diode exit is what is being specified most often in new spaces.  The reason is that they have an extremely long life where the LED lamps will last for 10 to 20 years and the correct amount of illumination that meets code.  They've also come down in price a lot as well.

For most older facilities that have not retrofitted to LED technology, there are still the incandescent variety which includes the 15T6 and the 20T6.5 lamps which have a tubular shape.  They were used for many decades as the lamp of choice in exit signs but much of that changed once more efficient light sources came about.  They are tubular in shape and hence the designation with the letter T.  They have a long filament inside which does make them vulnerable to things like vibration which is another reason people have been switching from those to fluorescent or LED sources.  We still have them available though and there are many people that still use them.  For those of you who may have these, you may want to consider going to a LED retrofit or to a fluorescent source and in some cases, if the sign is just really old, you may want to consider changing those out.  Another light source that was mentioned as one of the exit sign light bulbs used today are the Dulux or PL lamps that are a fluorescent light and operates on a ballast, but it too has largely been replaced by LED light source.  As with all fluorescent bulbs, they rely on ballasts inside of the fixtures or units to make them work. 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. 

One of the other types of exit sign light bulbs that was mentioned is something called self-luminous and it's really wrong to call it a light bulb anyway.  It's a tritium based isotope which is enclosed in a tubular element.  It really isn't a light bulb at all and it's an integral part of the exit, in other words, it's never replaced like a bulb.  It generally last for at least 25 years and is used a lot in places where there is no electrical line as these do not have any electrical connection because of the radioactive isotope which glows.  So self-luminous are great for areas where you can't get an electrical circuit to an area or some other kind of egress that is difficult to put an exit sign in. Remember that there are many types of exit sign light bulbs, we describe some the types used in commercial buildings here.  We have a large inventory of light bulbs for nearly every type of light fixture in the field.  If you need help identifying a bulb, our customer service representatives can help you determine what you have.