___ draft is created by a draft fan that pulls the gases of combustion through the furnace.

Mechanical draft is produced by ___.

Mechanical draft can be classified as ___.

The gases of combustion leaving a boiler that has natural draft are controlled by ___.

The induced draft fan is located ___.

Mechanical draft is used when burning ___.

The oldest form of draft used in a boiler is ___ draft.

The amount of draft produced in a natural draft system depends on the ___.

Air preheater is used to preheat air with the help of ______

When an insufficient (not enough) amount of air is supplied to a boiler, unburned fuel can create _________ deposits.

Dense (thick) white smoke leaving the stack in an indication that too much _____ is being supplied to the boiler.

A rotary air heater uses what is essentially waste heat to heat the air supplied to a boiler.

Name two commonly used types of oil heaters.

The flow of air and other gases through a boiler is commonly referred to as ________.

A ______ draft fan pushes combustion gases into a boiler.

An _______ draft fan draws(pulls) combustion gases out of a boiler.