Red Seal Gasfitter — Class A Practice Exam

How does altitude affect gas combustion efficiency?

1. Higher altitudes enhance combustion efficiency

2. Altitude has no effect on combustion

3. Higher altitudes can cause appliances to burn less efficiently

4. Lower altitudes create a need for more fuel

The correct answer is: Higher altitudes can cause appliances to burn less efficiently

At higher altitudes, the atmospheric pressure decreases, which in turn affects the availability of oxygen in the air. Gas combustion relies on a proper ratio of fuel to oxygen to burn efficiently. As altitude increases, the partial pressure of oxygen diminishes, leading to a reduction in the amount of oxygen available for combustion. Consequently, appliances operating at higher altitudes may not be able to achieve optimal combustion, resulting in a richer fuel mixture or incomplete combustion. This leads to the production of carbon monoxide and other byproducts, making combustion less efficient. Understanding this effect is crucial for gasfitters and service technicians who need to make necessary adjustments to appliances. These adjustments can include modifying burner settings or using altitudinal conversion kits to ensure that the appliance operates safely and efficiently despite the changes in atmospheric conditions.