What percentage of the tank's capacity is typically filled before an overfill prevention device activates?

• A. 80%
• B. 90%
• C. 95%
• D. 99%

Answer: (C)

The typical activation percentage for an overfill prevention device is usually set at 95% of the tank's capacity. This design ensures an ample safety margin, allowing for a small buffer before the tank reaches its maximum fill limit. By activating at 95%, the system helps prevent overfilling incidents that could lead to spills or accidents, which are critical in maintaining environmental safety and regulatory compliance.

When the tank reaches this level, the overfill prevention device will trigger, signaling operators to stop filling the tank or initiate other safety measures. This threshold is especially crucial in vapor recovery systems, where the prevention of liquid overfill is directly related to vapor emissions control. Understanding this percentage is essential for operators managing fuel storage tanks, as it directly impacts both safety protocols and compliance with hazardous materials regulations.