How Is Shielding Effectiveness Measured? A Guide to EN 50147-1 and IEEE 299
The only way to know whether a shielded room really works is to measure it. The measurement method step by step.
3 min readSeptember 23, 2026
Why Is the Gasket So Critical?
In a shielded room the metal walls stop signals easily; the real risk is where two parts meet. On every surface that opens and closes, such as a door frame, service panel or access hatch, a small gap is enough for a high-frequency signal to pass.
An RF gasket fills that gap with conductive material and ensures continuous electrical contact between two metal surfaces. A correctly chosen and maintained gasket preserves the room's measured performance for years.
Finger Stock Gaskets
Finger stock, made of beryllium copper or stainless steel, consists of thin leaves arranged in a row. When the door closes, each leaf presses against the mating surface, creating multi-point contact. It is one of the best-performing solutions at high frequencies.
Its drawback is mechanical sensitivity: the leaves can be crushed or get dirty. That's why heavily used shielded doors need regular cleaning and replacement of damaged leaves.
Knitted Wire and Conductive Elastomer
Knitted wire gaskets are made by knitting metal wire over a rubber core. They are flexible, inexpensive and easy to fit, making them suitable for fixed panels and access hatches. On doors that open very often, however, they flatten over time.
Conductive elastomer is silicone filled with silver, nickel or graphite particles. It provides both sealing against dust and moisture and shielding, which is why it's often chosen for outdoor enclosures and shielded containers.
Which One to Choose When?
If high frequency and high dB are the goal, a double row of finger stock on the main door is the safest choice. Knitted wire is used on fixed joints and conductive elastomer where environmental sealing is needed. Most projects combine all three.
Whichever gasket is chosen, performance is only proven by measurement. Checking gasket condition during annual maintenance and re-measurement is the most economical way to prevent leaks before they appear.
Frequently Asked Questions
How often are RF gaskets replaced?
It depends on use. On doors opened dozens of times a day, finger stock is renewed every few years; gaskets on fixed joints last much longer.
How are gaskets cleaned?
Dust and dirt are removed with a soft brush and a suitable cleaner. Oils or non-conductive sprays should not be used.
How can you tell a gasket has failed?
Crushed or broken leaves may be visible; a definitive answer comes from a shielding measurement around the door.
Let's Find the Right Solution for Your Project
Get a QuoteYour free site survey and quote will be ready within 24 hours.