Sealing Shielding

Sealing for Harsh Environmental Conditions in Telecommunications Applications

Outdoor telecommunications infrastructure - man on utility pole silhouette Parker HannifinOutdoor telecommunication infrastructures such as fiber optic boxes and electric enclosures often face many harsh environmental conditions. In environments where corrosive coastal air, flooding, and high humidity are common, telecom equipment is more prone to fungal attack. Fungus growth can severely deteriorate the conventional environmental seals such as foam and sponge gaskets, resulting in unprotected interior telecom components.

Therefore, sealing for outdoor telecommunication components is very crucial and is not as simple as keeping water out during a laboratory test. The seal has to exhibit excellent resistance to fungus while meeting other application requirements.

Testing requirements

Fungal and microbial

Fungal and microbial attack of elastomer products can be an issue in humid or tropical environments. Materials need to be tested to ASTM G 21-96, “Resistance to Synthetic Polymeric Materials to Fungi,” to ensure suitability for use in many of the world’s extreme environmental conditions.

ASTTM G-21-96 Resistance to Synthetic Polymeric Materials to Fungi, UL Ratings, Temperature Range, hardness, color



In addition to fungal attack, telecommunication equipment must also be protected from flame generated from either internal or external conditions due to its electrical components inside. In the event of a fire, the seal for telecommunication equipment must be able to self extinguish after the ignition source has been removed and must not create flaming drops or particles.

A good material to select would be one with a UL94 V-0 rating, a plastic flammability standard, to ensure regulatory compliance as well as safety for both the equipment and the surrounding areas. The V-0 standard is the most stringent UL flammability rating offered for elastomer products.

To pass the V-0 testing requirement, a seal has to stop burning within 10 seconds on a vertical specimen after the source is removed; drips of particles are allowed as long as they are not inflamed. In addition, the total afterflame time for the seal has to be less than or equal to 50 seconds.

Small box telecommunications enclosure showing seal and gasket - TechSeal Parker HannifinUL 94, released by Underwriters Laboratories of the USA, is the standard for safety of flammability of plastic materials for parts in devices and appliances testing. From the least flame retardant to the most flame retardant, there are six classifications. Please visit UL’s official website for the general descriptions of each classification and its testing requirement.


Afterflame – Persistence of flaming of a material, after the ignition source has been removed (Afterflame test – Time for each specification) Total afterflame time – The length of time for which a material continues to flame, under specified conditions, after the ignition source has been removed (Total afterflame time test – For 5 samples) Afterglow time – The length of time for which the material continues to glow under specific conditions, after the ignition source has been removed and / or cessation of flaming (Afterflame plus afterglow time test – For each individual specification after second flame application) Afterglow – Persistence of glowing of a material, after cessation of flaming or, if no flaming occurs, after the removal of the ignition source (Afterglow test – Afterflame or afterglow of any specification) Cotton indicator ignited by flaming particles or drops


One solution offered by Parker’s TechSeal Division is their S7395 material, which meets or exceeds all of the requirements for this harsh application.

It’s available in many standard low-closure force profiles including hollow O, hollow D, and many other custom engineered configurations. To learn more about this anti-fungal material, please contact TechSeal’s team of Application Engineers at (864) 573-7332 or Live Chat with our application engineers on our website


Additional resources:

Sealing Groove-less Applications with Flat Panel Gaskets

Seal Identification Methods: Part Printing | Sealing Fundamentals

Press-in-Place Seals Solve Problems for Automotive Applications

Sealing Fundamentals | How to Properly Install a Parker Hollow O-ring

What You Should Know About Advanced Bonding Technology

Manway Gaskets | Why Shippers Struggle


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