When you specify a museum display case, airtightness is one of the few performance characteristics that directly determines whether an artifact survives decades of display without micro-climate drift, dust ingress or pollutant attack. Yet many purchase orders still say only “well sealed” or “low air exchange.” That language is unenforceable. A proper museum display case airtightness testing report turns a vague promise into a measured, traceable number you can compare across suppliers and verify after delivery. This guide explains the test methods, the figures that matter, and the exact items to request before you sign off on a custom case.
Why Airtightness Is a Measured Specification, Not a Selling Point
Air leakage drives almost every deterioration pathway inside a case. Each exchange of outside air brings in moisture, sulfur compounds, ozone and particulate matter, and it pushes out whatever conditioned atmosphere you paid to create. Conservators generally describe case performance by air exchange rate (AER), expressed as the number of complete case-volume air changes per day. A loosely built case may sit at 1.0–3.0 AER; a well-engineered gasketed case typically reaches 0.1–0.5 AER; passive or active micro-climate cases aimed at tight humidity control often target below 0.1 AER, and some sealed designs achieve 0.01–0.05 AER. Without a test report, you have no way of knowing which band your case falls into.
There is also a commercial reason to insist on documentation. Airtightness depends on gasket compression, corner joinery, cable and sensor penetrations, door alignment and the quality of the seal around glass-to-frame interfaces. These are exactly the details that get cut when a factory is under cost pressure, and they are invisible once the case is installed. A report forces the discussion onto measurable ground.
Recognized Test Methods You Should See Named
The report should state the method explicitly, not merely say “tested.” The most common approaches for museum vitrines are:
- CO2 tracer gas decay — the case is sealed, CO2 is injected, and the decay curve is logged with a calibrated analyzer over several hours; AER is calculated from the gradient. This is the most widely used and least disruptive method.
- Pressure decay (pressure hold) — the case is pressurized slightly and the rate of pressure loss is recorded. Fast, quantitative, and useful for production screening.
- Constant concentration / flow measurement — used for very tight cases where decay methods become imprecise.
- Smoke or ultrasonic leak detection — qualitative only; acceptable as a supplementary check, never as the sole evidence.
Ask which instrument was used, its calibration status and date, and whether the test was performed on the finished case with gaskets, glazing and pass-throughs fully installed. A test on an empty frame proves nothing about the delivered product.
The Numbers and Conditions a Credible Report Must Contain
A test result without conditions is meaningless. Temperature and relative humidity affect gasket behavior and gas expansion, so the report should record ambient temperature, ambient RH, internal volume of the case in cubic meters or liters, and the exact air exchange rate with the calculation method shown. Demand the raw decay data or pressure curve as an appendix, not just a headline figure. At least three test runs, with the worst result quoted as the specification value, is a reasonable standard; a single favorable run should be treated with skepticism.
Also check what was installed during testing. Sensor feed-throughs, lighting cables, seismic anchors and humidity control modules all create leak paths. If the report shows testing before these were fitted, the number is optimistic. For cases that will hold moisture-sensitive material such as parchment, textiles or certain metals, insist on an AER result below 0.1 and a documented leak-check of every penetration.
Test Report Checklist: What to Request Before Sign-Off
Use this list in your purchase order or factory acceptance test protocol so nothing is negotiated after the fact:
- Named test method and the standard or in-house procedure it follows, with a written description.
- Instrument model, serial number, calibration certificate and calibration date.
- Test date, location and the names of the technicians who performed and witnessed the test.
- Case identification — model, size, glazing type, gasket material, and internal volume.
- Ambient temperature and RH during each run, plus the starting and ending internal conditions.
- AER results for at least three runs, with the average and the worst-case value both reported.
- Raw data appendix: decay curve or pressure-loss chart with timestamps.
- Confirmation that the case was fully assembled, including all cable and sensor penetrations.
- Photographs of the test setup and of the sealed case.
- For projects above roughly USD 20,000, an option for third-party witnessing or independent laboratory verification.
If a supplier cannot produce items 1–8, treat the airtightness claim as unverified. Reputable manufacturers will already have this documentation on file and can share a sample report from a comparable project.
Common Gaps Buyers Should Watch For
Several patterns recur in weak reports. Tests performed on a prototype rather than the delivered case. Results expressed only as “pass” against an undisclosed internal threshold. AER quoted without the internal volume, which makes comparison impossible. Reports missing the gasket specification, even though gasket compression set is the single most common cause of post-installation leakage. And reports that omit the aging question entirely: silicone gaskets typically hold performance for years, while cheaper EPDM or foam seals may compress permanently within 12–24 months. Ask whether the supplier re-tests after transport and installation, and request a recommended re-test interval, commonly every 12–24 months for high-value collections.
At Libafang Showcase Co., Ltd., cases are tested with the gaskets, glazing and cable pass-throughs installed, and full reports with raw data are issued as standard documentation. Comparing two quotes becomes far simpler when one includes a measured 0.08 AER and the other includes a promise.
Turning the Report Into a Contract Term
Write the airtightness figure into the specification as a maximum, not a target, and tie final payment to verification on site. A practical clause reads: the case shall achieve an air exchange rate no greater than 0.10 per day measured by CO2 decay on the fully installed unit, with a signed test report supplied before delivery and a re-test permitted within 30 days of installation. Add a remedy — re-sealing or replacement — so the requirement has teeth. For museums and luxury retail alike, that single paragraph does more to protect the collection than any amount of marketing copy, and it gives your facilities team a benchmark for future maintenance.
Planning a vitrine project and want to see what a complete test report looks like? Contact Libafang for a free design consultation and quotation, and we will include the airtightness specification and test documentation scope in your proposal.
