Gas Safe ACS - Accredited Certification Scheme Combustion Principles Questions and Answers

Question 1

Which of the following are the three essential components required for combustion, often referred to as the 'combustion triangle'?

Accepted Answer

Fuel, Heat, and Oxygen

Answer

Gas, Flame, and Ventilation

Answer

Carbon Dioxide, Water Vapour, and Nitrogen

Answer

Methane, Propane, and Butane

Question 2

An engineer is commissioning a new gas boiler. They observe a lazy, yellow-tipped flame on the main burner. What is the most likely cause of this?

Accepted Answer

Incomplete combustion due to insufficient primary air

Answer

Excessive gas pressure at the appliance

Answer

A blocked flue terminal, causing recirculation of products

Answer

High water content in the natural gas supply

Question 3

According to BS 7967, when using a portable flue gas analyser, what is the primary ratio used to assess the combustion safety of a gas appliance?

Accepted Answer

CO / CO2 ratio

Answer

O2 / N2 ratio

Answer

CO2 / O2 ratio

Answer

CH4 / O2 ratio

Question 4

What are the main products of the complete combustion of natural gas (methane)?

Accepted Answer

Carbon Dioxide (CO2) and Water Vapour (H2O)

Answer

Carbon Monoxide (CO) and Water (H2O)

Answer

Carbon (C) and Water (H2O)

Answer

Sulphur Dioxide (SO2) and Nitrogen (N2)

Question 5

A gas engineer is investigating a report of an intermittent smell of fumes from an open-flued gas fire. A spillage test is conducted. According to standard procedures, when should this test be performed?

Accepted Answer

After the appliance has been running at maximum rate for 5 minutes

Answer

Immediately after lighting the appliance from cold

Answer

Only when a flue gas analyser indicates high CO readings

Answer

With all windows and doors in the property wide open

Question 6

Under the Gas Safety (Installation and Use) Regulations 1998, what is the fundamental requirement regarding the air supply for a combustion appliance?

Accepted Answer

There must be an adequate supply for combustion and efficient working of the flue.

Answer

It must be mechanically supplied by a fan at all times.

Answer

It must be ducted directly from the appliance to outside.

Answer

The air supply must be filtered to remove dust particles.