Define the smoke point of kerosene precisely as used in fuel quality specifications for clean burning: identify the correct interpretation involving the flame height in a standard test lamp.

Introduction / Context:
Smoke point is a critical kerosene property for lamp burning and turbine fuels because it gauges the tendency to form soot. Higher smoke point indicates cleaner, smokeless flames under controlled test conditions and typically correlates with lower aromatic content.

Given Data / Assumptions:

• Standardized test lamp and wick configuration.
• Measurement in millimetres of flame height.
• No forced draft; normal atmospheric conditions during the test.

Concept / Approach:
The smoke point is not a time or a temperature. It is defined as the maximum flame height (in millimetres) at which the fuel burns without producing a visible smoky plume in a standard test lamp. The parameter serves as a specification limit in aviation kerosene and illuminating kerosene to ensure clean combustion.

Step-by-Step Solution:

Verification / Alternative check:
Fuel standards list minimum smoke points (e.g., in mm) for kerosene grades and aviation turbine fuels, aligning with this definition.

Why Other Options Are Wrong:

Common Pitfalls:
Confusing smoke point (a combustion cleanliness metric) with flash point (a safety volatility metric) or with freezing point (low-temperature operability).

Final Answer:
Maximum flame height in mm without smoking in a standard lamp