A combustion efficiency test includes the measurement of which of the following?

The correct response highlights the key components measured during a combustion efficiency test. This test is essential for determining how well a heating system burns fuel and dispenses energy.

Measuring carbon dioxide (CO2) levels is critical as it indicates the complete combustion of fuel; higher CO2 generally suggests better efficiency. Stack temperature is significant because it reflects heat losses; a lower temperature typically means that more heat is being used for heating instead of being lost up the chimney. Smoke is assessed to ensure that the system is not producing excessive particulate matter, indicating incomplete combustion. The measurement of excess air helps to determine how much air is being used in the combustion process; too much excess air can lead to inefficiency. Finally, draft is crucial as it affects the movement of combustion gases through the system, impacting overall efficiency.

Each of these elements contributes to understanding the combustion process's efficiency, leading to suggestions for maximizing energy use and minimizing emissions.