What is the maximum height for the bottom of an air inlet or exhaust opening in fuel dispensing areas?

The maximum height for the bottom of an air inlet or exhaust opening in fuel dispensing areas is crucial for ensuring proper ventilation and safety in locations where flammable liquids are present. Keeping the openings at a maximum height of 18 inches allows for adequate air flow while minimizing the risk of fuel vapors accumulating in a hazardous manner. This height is determined based on considerations such as the tendency of heavier-than-air vapors to sink and the need for fresh air to mix effectively with those vapors to prevent an explosive environment. Installing openings above this height could impede effective ventilation and lead to safety risks, while maintaining them at or below 18 inches helps facilitate the proper functioning of exhaust or air intake systems in these critical areas.