Engine-driven welders are generally used when electric power is not available for arc welding. Usually these are outdoor applications. However, engine-drive welders are often used for indoor applications when it is not convenient to supply power to electric "plug-in" arc welders. 

These indoor situations include everything from minor repair jobs to major plant shutdowns. When operating engine-driven welders indoors, vent the exhaust outside if at all possible, or use in large spaces with good ventilation.

The basic considerations when choosing an engine-driven welder are:

Application
Engine Type
Portability
AC Generator Power

Application

In trying to select an engine drive, the first thing to consider is the application. Ask yourself these questions:

Is this new construction or a repair job? Also, what is the size of the project?
Is there a particular welding process you would like to use? You may want to stick with a process with which you feel most comfortable, or there may be a certain process required on the job.
Is this a pipe welding project? The equipment chosen needs to produce an arc suitable for this type of work.
Will the job require arc gouging? Arc gouging is repair work usually done in industrial jobs.
What type of material needs to be welded? Most of the time the material will be a common mild steel plate. However, if it's aluminum, the welding will require different equipment.

Using this information, match it to the welding processes described below: