During storage of gasoline in atmospheric tanks, “breathing loss” refers to evaporative loss caused primarily by which condition?

Introduction:
Evaporative losses from gasoline storage contribute to product shrinkage and VOC emissions. Distinguishing mechanisms helps operators choose appropriate hardware (e.g., floating roofs, vapor recovery) and manage inventories accurately.

Given Data / Assumptions:

• Storage in atmospheric or fixed-roof tanks.
• Daily temperature swings are typical in outdoor installations.
• Gasoline is a volatile mixture with significant vapor pressure.

Concept / Approach:
“Breathing loss” arises when the vapor space expands with daytime heating and contracts at night. Expansion expels vapor-rich gas to the atmosphere; contraction draws in fresh air. This cyclic “tank breathing” is driven by ambient temperature fluctuation, independent of whether the incoming air is saturated or unsaturated.

Step-by-Step Solution:
1) Identify the physical driver: thermal expansion/contraction of vapor space.2) Link driver to environmental condition: day–night temperature fluctuation.3) Conclude that breathing losses are primarily caused by ambient temperature swings.

Verification / Alternative check:
Tank loss equations and emission inventories in standards (e.g., AP-42 style methodologies) explicitly relate breathing loss to temperature cycling and tank parameters (roof type, paint color, insulation).

Why Other Options Are Wrong:
Unsaturated air alone does not cause the cyclic volume exchange; temperature-driven expansion is the key factor.“Both” overstates the role of air saturation level.Sulfur content has no direct bearing on breathing loss magnitude.

Common Pitfalls:
Confusing breathing losses with working losses (due to filling/emptying); both contribute to total VOC emissions but have different operational drivers.

Final Answer:
Fluctuation of ambient temperature during day and night