Which of the following techniques have been employed to improve the efficiency of fireplaces?

addition of catalytic combustors

addition of boilers

use of masonry

use of venting systems

Addition of catalytic combustors and addition of boilers.

Explanation:

A fireplace is a masonry or prefabricated construction of metal and concrete that warms the environment. It is a domestic structure present in many houses, where a fire can be lit. It consists of a space lined with non-flammable materials such as stone and brick, to burn wood, and a chimney that lets smoke and other particles out. It was used for heating, cooking and lighting in old houses, but nowadays it is used mainly as decoration, or to heat houses in winter.

Over the years and advances in construction techniques, improvements were added to the construction of the fireplaces that made them more efficient. Among these improvements we can mention: addition of catalytic combustors and addition of boilers.

The first would be the right answer, all catalysts somehow boosts the performance