What thickness of steel smokestacks requires air terminals under standard LPI-175?

The requirement for installing air terminals on steel smokestacks is primarily based on their thickness to ensure effective lightning protection. When smokestacks are less than 3/16 inches thick, they are considered more susceptible to the effects of a lightning strike, including damage and potential structural failure. Consequently, the standard LPI-175 mandates that air terminals must be installed on these smokestacks to provide additional protection.

This requirement is in place to enhance safety; since thinner steel structures are generally less robust and may not be able to adequately withstand the thermal and mechanical forces that occur during a lightning strike. By ensuring that air terminals are placed on smokestacks of this thickness, the design integrates a systematic approach to reduce the risk of damage and ensure the reliability of the structure.

For thicker smokestacks, such as those measuring 1/4 inch thick or greater, the need for air terminals becomes less critical, as these structures are less likely to suffer significant damage from lightning. This guideline helps professionals in the field identify when additional protective measures are necessary based on the physical characteristics of the infrastructure being protected.