RF-shielded enclosures and semi-anechoic EMC test chambers · shielding effectiveness in dB by frequency (IEEE 299 / EN 50147-1 methods), 3 m and 10 m ranges, normalized site attenuation (NSA) within ±4 dB, hybrid ferrite absorber, RF doors, power-line filters
An EMC test chamber is a radio-frequency shielded room — a modular steel enclosure with RF doors, filtered power and signal entries and ventilation waveguides — that keeps outside signals out and test signals in. Lined with absorber on walls and ceiling over a metal ground plane, it becomes a semi-anechoic chamber for radiated emissions and immunity testing at 3 m or 10 m range. Ask three things first: the shielding effectiveness in dB at each frequency band and how it will be verified; the range length, quiet zone and site-validation tolerance (NSA, sVSWR, field uniformity); and the door, filter and floor-load requirements of the equipment you will test.
RF-shielded rooms and enclosures for EMC and EMI testing, semi-anechoic and fully anechoic EMC chambers at 3 m, 5 m and 10 m range lengths, and their doors, filters, absorber and acceptance tests. Small benchtop shield boxes, reverberation chambers, antenna-measurement (far-field and compact-range) chambers, MRI shielding and acoustic rooms are outside this page except where compared.
CNFX editorial research · Sources checked October 11, 2026 · 6 sources
Specify shielding effectiveness by frequency and test method
ETS-Lindgren's Series 81 RF shielded enclosure datasheet gives shielding performance by field type: magnetic field 20 dB at 1 kHz, 56 dB at 14 kHz and 100 dB at 100 kHz; electric field 110 dB from 14 kHz to 30 MHz; plane wave 110 dB from 30 MHz to 1 GHz; microwave 110 dB at 1 GHz and 100 dB from 10 GHz to 40 GHz. Each enclosure is built from 1.9 cm (0.75 in) panels of high-density particle board or plywood laminated with 28-gauge galvanized steel, joined by a hat-and-flat clamping system with screws every 10.16 cm (4.0 in), isolated from the floor by a 6-mil dielectric vapor barrier and 3.175 mm dielectric underlayment, offered in 36 standard configurations, and upgradable to a ferrite- or absorber-lined anechoic chamber. [1] IEEE 299 (the 1997 edition, superseded by IEEE Std 299-2006) provides uniform procedures for measuring the effectiveness of shielding enclosures from 9 kHz to 18 GHz, extendable to 50 Hz and 100 GHz, for enclosures with no dimension less than 2.0 m, covering single- and double-shield, bolted, welded or building-integral construction in steel, copper, aluminium, screening, foil or fabric. [4] EN 50147-1 applies to shielding-attenuation measurement of shielded enclosures from 9 kHz to 40 GHz, establishing a single agreed procedure for validating shielding effectiveness. [5]
Editorial calculation: shielding effectiveness in dB for field strength is 20 × log10 of the field ratio, so 100 dB corresponds to a reduction by a factor of 10^5 (100,000) and 110 dB to about 316,000; the magnetic-field value of 20 dB at 1 kHz is a factor of 10. [1]
In a 10 m chamber for TÜV Rheinland, ETS-Lindgren lists a shield verification test of the chamber referencing the test methods of MIL-STD-285/ IEEE-299 at 1, 6, 10 and 40 GHz, and states that the control, amplifier and support rooms were tested in accordance with the same methods at 1 and 10 GHz. [3]
Give the supplier the shielding effectiveness required at each frequency band (magnetic, electric, plane wave, microwave), the test standard and test points for acceptance (IEEE 299, EN 50147-1 or MIL-STD-285), single or double shield, panel construction, and every penetration: doors, power and signal filters, waveguide vents, fibre and cable entries.
02
Specify range length, quiet zone and site validation
A NICT paper on site validation explains that radiated emission measurement from 30 MHz to 1 GHz is made over a metal ground plane, with a receiving antenna a standard distance (for example 10 m) from the equipment under test, either outdoors or in a semi-anechoic chamber; for normalized site attenuation (NSA) validation of a compliance test site, the difference between calculated theoretical values and values measured at the site must be within 4 dB, and under the reference site method a site is accepted if its measurements are within ±4 dB of those at a reference test site. NICT's own semi-anechoic chamber has a shielded room of 28.5 m × 17.0 m × 11.7 m with ferrite tiles and 2.5 m hybrid absorbers. [6] ETS-Lindgren's FACT 3 datasheet describes a 3 m path-length chamber using hybrid absorber and ferrite tile, a frequency range of 9 kHz to 40 GHz, quiet zones of 1.2, 1.5 or 2.0 m, NSA performance options of 4.0 dB, 3.5 dB (Plus) and 3.0 dB (Premium) per ANSI C63.4, field uniformity of 0–6 dB from 80 MHz to 18 GHz over a 1.5 m × 1.5 m test plane, and a shielded room of 8.53 m × 6.10 m × 5.64 m; acceptance options include NSIL (9 kHz–30 MHz) per CISPR 16-1-4, NSA (30 MHz–1 GHz) per ANSI C63.25.2 and CISPR 16-1-4, and sVSWR (1–18 GHz) per ANSI C63.25.1 and CISPR 16-1-4. [2]
For TÜV Rheinland, ETS-Lindgren built a 10 m chamber with 3 m and 10 m ranges, a 5 m quiet zone and ±3.0 dB NSA, measuring 21.8 m × 13.9 m × 9.6 m overall including support structure, with NSA tests for one 3 m and two 10 m ranges per ANSI C63.4, sVSWR per CISPR 16-1-4 at 3 m, field uniformity per IEC 61000-4-3 from 1 to 18 GHz and ambient emissions from 150 kHz to 40 GHz. [3]
Editorial calculation: wavelength equals 300 ÷ frequency in MHz (metres), so the 30 MHz–1 GHz NSA band spans wavelengths from 10 m down to 0.3 m — the low end is where absorber depth and ferrite tiles matter. [6]
State the range length (3 m, 5 m or 10 m), quiet-zone diameter and height, NSA tolerance (±4 dB or tighter), sVSWR and field-uniformity requirements, the standards your lab will test to (CISPR, ANSI C63.4, FCC, IEC 61000-4-3, automotive), turntable diameter and load, and antenna-mast height.
03
From modular shielded rooms to full semi-anechoic chambers
The two listed makers show shielded rooms (one welded, one described as an EMC shielded room); chamber-scale examples on this page come from ETS-Lindgren's published projects.
The reviewed sources show a span from modular shielded rooms of 2.52 m × 2.50 m × 2.51 m upward to compact 3 m chambers and 10 m chambers of 21.8 m overall length. [1][2][3] When requesting quotations, ask each supplier for shielding test reports from a comparable installation, NSA and sVSWR data with the quiet zone stated, absorber model and depth, door and filter datasheets, floor-load and building interface drawings, and installation and re-verification terms.
04
How shield panels, absorber, doors and filters fit together
Shielding, size, doors and filters: what the chamber quote must list
Shielding, dimensions, doors, filters and floor loads have published examples from ETS-Lindgren; HVAC, humidity, power supply and weight do not, and have to be agreed for your building.
Field
What it means and published values
Ask the supplier for
Shielding effectiveness
100–110 dB by field type; 20 dB at 1 kHz magnetic. [1]
dB per band, test method.
Internal dimensions
8.53 × 6.10 × 5.64 m (3 m chamber); 2.52 × 2.50 × 2.51 m smallest standard room. [2][1]
Send the test standards, range and equipment size together
Paste it into your enquiry below or into an email to a maker, then replace every bracket.
Use: [emissions; immunity; both; standards]
Range: [3 m; 5 m; 10 m; quiet zone]
Shielding: [dB per band; IEEE 299 / EN 50147-1 test points]
Site validation: [NSA ±dB; sVSWR; field uniformity]
Doors: [equipment door W × H; personnel door]
Filters: [A; V; phases; signal lines]
Building: [space; floor load; HVAC]
Quantity and schedule: [rooms; date]
Changzhou Leining Electromagnetism Screen Equipment shows a welded shielded room, and Wuxi Anxin Shielding Equipment an EMC shielded room, on product pages of their own websites.
Explore company information and manufacturing capabilities, then discuss the scope of your project with a relevant supplier.
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Compiled and source-reviewed by the CNFX editorial team.
Each manufacturer above links to the page on that company's own website where the product is listed, with the date we checked it. How we source and review
· Page last updated 13 October 2026
Buyer questions
What shielding effectiveness do modular shielded rooms reach?
ETS-Lindgren's Series 81 datasheet lists 110 dB from 14 kHz to 1 GHz (electric and plane wave) and 100 dB from 10 to 40 GHz. [1]
What NSA tolerance must an EMC chamber meet?
Measured NSA must be within 4 dB of the calculated theoretical value for a compliance test site, per a NICT site-validation paper. [6]
Which standards measure shielding effectiveness?
IEEE 299 covers 9 kHz to 18 GHz for enclosures of at least 2.0 m; EN 50147-1 covers 9 kHz to 40 GHz. [4][5]
Sources and what still needs a direct check
Sources checked 2026-10-11. Sources are three ETS-Lindgren datasheets and case studies, the IEEE 299 and EN 50147-1 standard summaries, and a NICT (Japan) site-validation paper.
