What is a shielded enclosure?

A shielded enclosure is a box, cabinet, tent, or room whose walls form a continuous conductive barrier against radio frequency (RF) and electromagnetic interference (EMI). It keeps outside signals from reaching what is inside, and keeps signals from inside from getting out. Common types include benchtop RF test enclosures (shield boxes), walk-in shielded rooms, Faraday tents, and shielded racks and cabinets.

Is a shielded enclosure the same as a Faraday cage?

It works on the same principle. A Faraday cage is the general idea of a conductive enclosure that blocks external electric fields. A shielded enclosure is a practical product built on that idea, with engineered doors, filtered cable entries, and shielded vents so it can be used every day while keeping its performance.

What does an attenuation figure in dB mean?

Shielding effectiveness is the ratio between the field strength without the shield and with it, expressed in decibels. Every 20 dB is a tenfold reduction in field strength, so 60 dB means the field inside is about one thousandth of the field outside. Figures are quoted across a frequency range, and often separately for magnetic fields, electric fields, and plane waves, so compare them at the frequencies you actually care about.

What frequency range do shielded enclosures cover?

It depends on the enclosure. Many are specified from the low kHz range up into the GHz range, while benchtop shield boxes are often specified for the cellular, Wi-Fi, and other wireless bands their users test. Low-frequency magnetic fields are the hardest to block and may need thicker or magnetic metals, so state the lowest frequency you need when you ask for a quote.

What is the difference between a shield box and a shielded room?

A shield box is a closed benchtop or rack-mounted enclosure for one device or a board, used heavily in wireless device development and production testing. A shielded room is large enough for people and equipment, usually built from modular panels inside a building, and is used for EMC testing, secure communications, and other work that does not fit in a box.

Why do doors and cable entries matter so much?

The walls of a well-built enclosure rarely limit its performance. Gaps do. Door seals, seams between panels, cable penetrations, and vents are where signals leak. Doors use finger stock, knife-edge contacts, or inflatable seals; cables pass through filters or fiber optic feedthroughs; and vents use honeycomb waveguides that pass air but block RF below their cutoff frequency.

How is a shielded room tested?

Shielding effectiveness of enclosures is commonly measured with the method in IEEE Std 299, which replaced the older MIL-STD-285. A transmitter is placed on one side of the wall and a receiver on the other, and the signal is compared with and without the shield at the specified frequencies. Rooms are tested on completion and should be re-tested periodically and after any change.

Can I add a new cable or penetration later?

Yes, but it has to be done through a proper shielded penetration such as a filter, a bulkhead connector, a waveguide, or a fiber feedthrough, ideally by the enclosure supplier. Drilling a hole and passing a cable through can let in enough interference to undo most of the shielding. Re-test after the change.

When is a Faraday tent a better choice than a rigid enclosure?

A Faraday tent made of metallized fabric folds for transport and sets up quickly, so it suits temporary test areas, field work, and digital forensics teams that move between sites. Rigid steel or panel enclosures generally hold their performance better over years of heavy daily use and accept more doors, filters, and equipment.

How is MRI shielding different from EMC shielding?

An MRI RF shield is built into the walls, floor, and ceiling of the scanner room to keep outside radio signals from showing up as image artifacts. Scanners work at specific frequencies, around 64 MHz for a 1.5 tesla magnet and 128 MHz for 3 tesla. The shield is part of the scanner installation, and the magnetic field itself is handled separately by the magnet design and, where needed, separate magnetic shielding.

What does a shielded enclosure for digital forensics do?

Forensics teams isolate seized phones and tablets from cellular, Wi-Fi, and Bluetooth networks so they cannot be remotely wiped or receive new data while they are examined. Benchtop enclosures with glove ports, Faraday tents, and shielded rooms are all used, depending on how many devices are handled and where.

What should I send to get a quote?

Describe what goes inside the enclosure, the frequency range and attenuation you need, the cables and utilities that must enter, how often it will be opened, and where it will be installed. For rooms, include approximate dimensions and ceiling height. That is enough for a supplier to suggest a type and size and come back with a quote.

Disclaimer and terms of use

Last updated 22 October 2026

Information only, not advice

Everything on this site is general information provided for educational purposes only. It is not engineering, electrical, EMC, security, medical, safety, legal or other professional advice.

Do not rely on this site to specify, select, install, test or operate any enclosure or equipment. Always follow the manufacturer's instructions, your test, security and accreditation requirements, the applicable codes and standards, and the judgment of a qualified engineer. Security facilities are approved by their accrediting authority, and MRI shielding is coordinated with the scanner manufacturer; nothing on this site replaces either.

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Shielded enclosures and their installation carry real hazards, including heavy doors and panels, pinch points, lifting, electrical work on filters and power feeds, exposure to RF from test transmitters, and enclosed spaces with limited ventilation. Follow the manufacturer's instructions, electrical and lockout procedures, RF exposure limits, and applicable occupational safety regulations. Nothing on this site replaces them.

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