What is one of the primary indicators of improper combustion in a gas appliance?

Visible soot around a gas appliance is indeed one of the primary indicators of improper combustion. When combustion is not occurring efficiently, it can lead to incomplete burning of the fuel. This incomplete burning can create soot, which is a byproduct of carbon that does not fully oxidize.

The presence of soot is significant because it points to potential safety issues, such as the release of carbon monoxide, a dangerous and toxic gas that can occur when combustion is not complete. Soot buildup can also indicate that the appliance may not be venting properly, leading to further risks and potential appliance malfunction.

In contrast, blue flames generally indicate that combustion is occurring properly, suggesting complete combustion where gas is burning efficiently. Odorless combustion may lead to misconceptions about safety, as it does not inherently indicate proper or improper combustion. High gas pressure readings, while important for the functionality of the appliance, do not directly indicate the quality of the combustion process itself. Hence, visible soot serves as a crucial warning signal in assessing appliance performance and safety.