What is the minimum height above grade for ducts conveying explosive or flammable vapors?

The minimum height above grade for ducts conveying explosive or flammable vapors is established to ensure safety and reduce the risk of fire hazards. In scenarios where ducts may be exposed to potential ignition sources, having them at a height of 10 feet above grade helps to mitigate risks associated with vapors mixing with air at lower levels where ignition could occur. This height allows for greater dispersion of any potential leaks or fumes, reducing the chance of accumulation that could lead to an explosion or fire.

This standard is informed by safety regulations that take into account factors like the density of the vapors, the likelihood of exposure to ignition sources, and overall site safety requirements. Thus, maintaining ducts at this specified height aligns with best practices aimed at protecting both the structure and individuals working in or near such environments.