A shielding effectiveness test report is the document that decides whether a shielded room, SCIF, or MRI suite gets accepted, paid for, and put into service. Yet many specifiers receive one and skim only the final "PASS" line, missing the detail that determines whether the result is meaningful or whether a single weak frequency is being quietly averaged away. Reading the report properly is the difference between accepting a verified asset and accepting an unverified claim.
The report is not complicated once you know what each section is for. It is fundamentally a table of required versus measured attenuation across a set of frequencies, wrapped in metadata that establishes credibility — the standard followed, the equipment used, and how it was calibrated. This guide explains the anatomy of a shielding effectiveness test report, how to interpret attenuation by frequency, what a failing point actually means, and what a specifier should insist on before accepting one.
What a Shielding Effectiveness Test Report Is
A shielding effectiveness (SE) test report is the formal document recording the measured attenuation of a shielded enclosure at specified frequencies, compared against the required values, with a pass or fail determination for each point. It captures the test scope, the standard followed (typically IEEE Std 299), the instrumentation and its calibration, the measurement locations, and any deficiencies, so that the enclosure's performance is documented in a defensible, repeatable form.
The report turns shielding from an assertion into evidence. "The room provides 100 dB" means little; a report showing 100+ dB measured against an 80 dB requirement at twelve frequencies across three regimes, taken with calibrated equipment to IEEE 299, is verifiable proof. It is the deliverable that closes out RF shielding acceptance testing and the record an owner relies on for warranty and accreditation. National Shielding produces these reports through its RF/EMI testing services.
Anatomy of the Report
A credible SE report has a predictable structure. Each element exists to answer a question a specifier or auditor will eventually ask, and a report missing any of them is harder to trust.
- Scope and identification — what enclosure was tested, where, when, and for whom; the room's dimensions and construction type.
- Standard used — the measurement method, almost always IEEE Std 299 (or IEEE 299.1 for small enclosures), establishing how the numbers were obtained.
- Required specification — the attenuation the enclosure must achieve at each frequency, drawn from the project spec or governing standard.
- Test equipment and calibration — the signal generators, receivers, and antennas used, with calibration dates and traceability, proving the instruments were trustworthy.
- Frequency points and field type — each tested frequency, the field type (magnetic, electric, or plane wave) and polarization, and the measurement location.
- Required vs measured dB and pass/fail — the core data table, giving both values and a verdict at every point.
- Deficiencies and remediation — any failing points, their locations, and the corrective action and re-test results.
- Sign-off — the technician, date, and a final acceptance statement.
The measurement method behind these numbers is worth understanding in its own right; our guide to IEEE 299 shielding effectiveness testing explains the antennas and geometry that produce each reading.
Reading a Sample SE Report Table
The heart of any report is the data table. The example below shows a representative excerpt for a room specified at 80 dB minimum across its band. Note how the field type changes with frequency — magnetic at low frequency, electric/plane wave higher up — exactly as IEEE 299 prescribes.
| Frequency | Field Type / Polarization | Required (dB) | Measured (dB) | Pass/Fail |
|---|---|---|---|---|
| 10 kHz | Magnetic (H-field) | 20 | 34 | Pass |
| 100 kHz | Magnetic (H-field) | 40 | 58 | Pass |
| 1 MHz | Magnetic (H-field) | 60 | 71 | Pass |
| 30 MHz | Electric (E-field) | 80 | 96 | Pass |
| 100 MHz | Electric, vertical | 80 | 78 | Fail |
| 400 MHz | Plane wave, horizontal | 80 | 101 | Pass |
| 1 GHz | Plane wave, vertical | 80 | 104 | Pass |
| 10 GHz | Plane wave, horizontal | 80 | 92 | Pass |
This excerpt illustrates two essential reading habits. First, the required value rises with frequency in the low range — a magnetic-field spec of 20 dB at 10 kHz is not a weakness, it reflects how much harder low-frequency magnetic shielding is to achieve. Second, the single 100 MHz failure (78 dB against an 80 dB requirement) means the room as a whole fails, even though every other point passes comfortably. A report's verdict is governed by its worst point, not its average.
Interpreting Attenuation by Frequency
Shielding effectiveness is not a single number; it is a curve. Understanding the shape of that curve tells you where a room is strong and where it is vulnerable.
- Low frequency (magnetic field) — typically the lowest dB values. Thin conductive walls attenuate low-frequency magnetic fields poorly, so specs here are modest and this is where many rooms are weakest. Critical for MRI suites and some secure environments.
- Resonant range — performance can dip sharply at frequencies where the enclosure or its apertures resonate. A report that samples densely through this band is more trustworthy than one that skips it.
- High frequency (plane wave) — usually the highest dB values, but also where small apertures — door gaps, vents, penetrations — leak. A high-frequency failure points to an aperture problem rather than a bulk-wall problem.
This is why field type matters as much as frequency. A failure in the magnetic regime implies a barrier-material or thickness limitation, while a failure at microwave frequencies almost always implies a leaking aperture — a door, gasket, or penetration. The diagnostic difference shapes the remediation, and the underlying material choices are compared in our overview of comparing RF shielding materials within our shielded rooms for EMC compliance laboratories guide.
What a Failing Point Means and What to Require
A single failing frequency does not necessarily condemn the room — but it does mean the room is not yet acceptable. The failure localizes the problem: a low-frequency magnetic shortfall suggests the barrier itself, while a high-frequency dip at one measurement location usually points to a specific door, seam, or penetration near that probe. Good reports record the location of each failing point precisely enough to direct remediation, after which only the affected points are re-tested and the report updated.
As a specifier, there are concrete things to require before accepting any SE report. Insisting on these up front prevents disputes later.
- The governing standard named explicitly (IEEE 299 or 299.1), not just "industry standard."
- Required versus measured dB at every frequency, with the pass/fail verdict per point — not a single summary figure.
- Field type and polarization for each reading, confirming the right physics was measured in each band.
- Test equipment list with current, traceable calibration dates.
- Measurement locations identified, including the specific probing of doors, seams, and penetrations.
- Full documentation of any deficiencies and their re-test results, not just the final pass.
A report meeting all six is a defensible record of performance; one missing several is an assertion dressed as evidence.
Frequently Asked Questions About Shielding Effectiveness Test Reports
What is a shielding effectiveness test report?
It is the formal document recording a shielded enclosure's measured attenuation at specified frequencies against the required values, with a pass or fail result at each point. It also captures the test scope, the standard used (typically IEEE Std 299), the calibrated equipment, the measurement locations, and any deficiencies, providing defensible proof of the room's performance.
How do I read the pass/fail criteria in an SE report?
Compare the measured dB to the required dB at every individual frequency and location. The point passes only if the measured value meets or exceeds the requirement, and the entire enclosure passes only if every point passes. A report's overall verdict is governed by its worst-performing point, not by an average, so a single failure means the room is not yet acceptable.
Why are the required dB values lower at low frequencies?
Because low-frequency magnetic fields are inherently much harder to attenuate than high-frequency electric fields. Thin conductive walls do little against magnetic fields below a few hundred kilohertz, so specifications set modest dB requirements there. A lower required value at 10 kHz than at 1 GHz reflects shielding physics, not a weaker specification.
What does a single failing frequency mean?
It means the room does not yet meet specification, but it also localizes the problem. A low-frequency magnetic failure points to the barrier material or thickness, while a high-frequency failure at a specific location usually indicates a leaking aperture such as a door, gasket, or penetration nearby. The failure's frequency and field type guide the remediation.
What standard should an SE test report cite?
It should cite IEEE Std 299 for walk-in enclosures, or IEEE Std 299.1 for small enclosures and cabinets. The report should name the standard explicitly rather than referencing a vague "industry practice," because the standard defines the antennas, geometry, and procedure that make the measured numbers meaningful and comparable.
What should specifiers require in a shielding test report?
Specifiers should require the named standard, required-versus-measured dB at every frequency with per-point pass/fail, the field type and polarization for each reading, a calibrated equipment list with traceable dates, identified measurement locations including doors and penetrations, and full documentation of any deficiencies and their re-test results. A report missing these elements is an assertion rather than verified evidence.
Does an averaged dB figure indicate a room passed?
No. A single averaged figure can hide a failing frequency, because averaging high readings across most of the band can mask one critical dip. Acceptance depends on the worst point meeting its requirement, so a legitimate report shows every individual frequency and location rather than a single summary number.