For a smog check, what is the correct interpretation of visible smoke?

Visible smoke during a smog check is significant because it can indicate underlying engine problems that affect the vehicle's emissions performance. This smoke often suggests incomplete combustion within the engine, which can lead to higher levels of harmful pollutants being emitted into the atmosphere. For example, blue smoke typically indicates that oil is burning in the combustion chamber, while black smoke suggests an overly rich fuel mixture. Both conditions can impair the engine's efficiency and contribute to increased emission levels, which is critical when assessing whether the vehicle meets the smog check standards. Thus, the presence of visible smoke is a key indicator that warrants further investigation of the vehicle's mechanical health and overall emissions control system.