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Active Air Terminals: What the Standards Say
An active air terminal is a product with an extra device at its tip rather than a plain metal rod. This article looks at what DSTU EN 62305-3:2021 relies on when air terminations are positioned and what follows for choosing a lightning rod on a mast.
An active air terminal is an air terminal with an additional device at the tip, as opposed to a plain metal rod. DSTU EN 62305-3:2021 sets the protection zone by three methods: the protection angle, the rolling sphere and the mesh.
Contents
What the standards rely on
Under DSTU EN 62305-3:2021 (cl. 5.2.1) an air-termination system may consist of any combination of rods (including free-standing masts), stretched wires and meshed conductors. They are positioned by one or more of three methods (cl. 5.2.2): the protection angle, the rolling sphere or the mesh.
Each method has limits. The rolling sphere is acceptable in all cases. The angle suits simple-shaped buildings and is limited by the height of the air terminal. The mesh suits flat surfaces. Sphere radius, cell size and angle depend on the LPS class (Table 2, Figure 1), and the figures by class are collected in the article on calculating the protection zone.
What “active” means
The name is given to an air terminal with an additional device at the tip. It is the name of a product type.
That is only the name of a product type. How much it protects is shown not by the wording on the packaging but by the method used to set the zone in the design.
What the standard says about the size of the zone
For all types of air terminals, the protected volume is determined only from the real dimensions of the metal elements of the air-termination system (DSTU EN 62305-3:2021, cl. 5.2.1). So the calculation uses the actual height and shape of the metal.
For placing air terminals, cl. 5.2.2 names three methods: the protection angle, the sphere and the mesh. Whether a particular design accepts such a product, and with what justification, is for the lightning protection designer to decide.
How to confirm the protection zone
The zone is confirmed by a calculation using one of the three methods. A rough estimate of the radius under the sphere method is available in the protection zone calculator, but the full calculation for a real object with several air terminals is done by an engineer from the text of the standard.
Which standards are in force now is covered in the overview of the standards. The difference between an air terminal, a lightning rod and a lightning mast is explained in the article on terms.
What to choose for a mast
For a lightning rod on a mast it is easier to start from the methods named in the standard: the height of the shaft, and so of the air terminal, is checked by a calculation using the sphere, angle or mesh method; for the angle method the height is limited (Table 2, Figure 1). How a steel mast works as an air terminal and down-conductor is covered in a separate article on the steel mast as a lightning rod.
The POLYGONAL company manufactures lightning rods on multi-sided bent shafts and masts, with more in the air terminals and lightning rods section. Send the height, the site and details of the object to be protected, and we will select the shaft. Installation is carried out by a licensed construction partner company.
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Active air terminals: frequently asked questions
What is an active air terminal?
It is an air terminal with an additional device at the tip, as opposed to a plain metal rod. The name describes a type of product.
Is an active air terminal one of the methods in DSTU EN 62305-3?
Clause 5.2.2 of DSTU EN 62305-3:2021 names three placement methods: the protection angle, the rolling sphere and the mesh. We did not find a separate method for active air terminals among them.
How is the protection zone of an air terminal determined?
By one of the three methods of the standard: the rolling sphere, the protection angle or the mesh. The protected volume is based on the real dimensions of the metal elements (cl. 5.2.1).
What can an air-termination system consist of under the standards?
Rods (including separate masts), stretched wires and meshed conductors in any combination, positioned by the angle, sphere or mesh method (cl. 5.2.1 and 5.2.2).
Can I install an active air terminal instead of a plain rod?
That is a decision of the lightning protection design, made by the designer with proper justification. Do not swap an air terminal on site yourself, least of all at height.
What should I send to have a lightning rod shaft selected?
The height and site, the dimensions of the object to be protected and the LPS class from the design, if it is already set.
Related products: Lightning protection masts and air-termination rods
More on this topic: Lightning Protection Norms: Why the Old Standard Was Withdrawn and What Applies Now · Calculating a Lightning Rod's Protection Zone: Methods and an Example · Lightning Protection of Masts and Towers: Choosing a Lightning Rod · A Steel Mast as Air-Termination and Down-Conductor per DSTU EN 62305-3 · Lightning Protection Inspection and Maintenance: Intervals, Checks, Records · Lightning Rod, Air Terminal, Lightning Protection: What's the Difference
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