Fire safety property comparison: Among petrol (gasoline), kerosene, diesel, and furnace oil, which product has the highest flash point under standard test conditions?

Introduction / Context:
Flash point is the lowest temperature at which a liquid gives off sufficient vapour to ignite momentarily. It increases as products become heavier and less volatile. This property informs storage and handling classifications and safety practices in refineries and depots.

Given Data / Assumptions:

• Products considered: petrol, kerosene, diesel, furnace oil.
• Standard closed-cup or open-cup methods as per product specs.
• Comparison is qualitative: identify the highest flash point product.

Concept / Approach:
Light products (petrol) have very low flash points, kerosene is higher, diesel higher still, and residual fuels such as furnace oil exhibit the highest flash points due to minimal volatility at ambient conditions. Hence, furnace oil tops the list for flash point among the given options.

Step-by-Step Solution:

Verification / Alternative check:
Typical specification ranges: petrol has a very low/negative flash by design; kerosene around tens of °C; diesel higher; furnace oil significantly higher still, often exceeding 60–90°C depending on grade.

Why Other Options Are Wrong:

Common Pitfalls:
Confusing “flash point” with “autoignition temperature”; these are different properties with different trends.

Final Answer:
Furnace oil (residual fuel oil)