There are basically 3 different types of gas fireplaces: 

 

    Millivolt System Gas Fireplaces

    Standard System Gas Fireplaces

    IPI System Gas Fireplaces

 

Probably the easiest way to tell which type of system your gas fireplace uses  is to determine how you would normally operate it.

With a millivolt or IPI system, you would normally turn the main burner flame on and off with a wall switch  where a standard system involves physically turning a knob or lever to turn the flame on and off (we will explain how each of these systems works later).

The difference between a millivolt or IPI system is whether you have a standing pilot light or not.  Millivolt systems have a pilot light (that tiny little flame that runs constantly) and would normally have to be re-lit if it were to go out.  IPI systems have no pilot light until you turn on your wall switch.  With IPI, your pilot will electronically light itself after you flip on your wall switch.  IPI is a relatively new system.