What is the minimum horizontal clearance from combustible material for an unlisted outdoor open flame illuminating appliance with a flame height of 24 inches above the burner head?

For an unlisted outdoor open flame illuminating appliance with a flame height of 24 inches above the burner head, the minimum horizontal clearance from combustible materials is set to be 3 feet. This distance is necessary to ensure safety and minimize the risk of ignition of nearby combustible materials. The regulations are based on the understanding that flame could cause heat and sparks, leading to potential fire hazards.

In an outdoor setting, where wind patterns can influence the flame and its heat dissipation, maintaining this clearance helps ensure that any nearby flammable materials remain at a safe distance, reducing the risk of fire. Standards are designed with a conservative approach to prioritize safety, hence the requirement for 3 feet of clearance in this case, which accounts for both the flame height and safety margins for unexpected conditions.