Is the fire pit or fireplace approved for use in screened porches, gazebos, and lanais?

The unit itself is not UL approved for this application, but there should not be any problem provided the following guidelines are followed:

A minimum of three walls are screened. Screens must be permanently open. They cannot have windows that can close.
The screened walls must provide a minimum open area of 30%.
All appliance ceiling and wall clearances must be met.
Minimum porch area 96 square feet.