Choose a vacuum seal using outgassing evidence for the specific compound and sample condition. The report must identify what was measured, under which exposure, and how the result relates to your equipment. A polymer name, cleanroom classification or hardness value does not answer those questions.
For optical instruments and other contamination-sensitive equipment, begin with the affected function: an optical surface, process chemistry, pump-down requirement or another defined acceptance criterion. That determines which measurements are useful.
Identify the output before comparing the numbers
Outgassing results can describe different quantities. NASA's outgassing database description distinguishes total mass loss, collected volatile condensable material and water-vapour regain under a defined test procedure for spacecraft materials. These are separate outputs, not interchangeable names for one result.
| Reported output | What to establish before comparison |
|---|---|
| Total mass loss, expressed as a percentage | Initial sample mass, exposure and the basis of the percentage |
| Collected condensable material | Collection arrangement, temperatures, exposure and reported normalization |
| A mass or gas-release rate | Time basis, units, exposed area or mass, temperature and measurement method |
| An assembly contamination or vacuum result | Installed configuration, other materials present and the equipment acceptance criterion |
A cumulative percentage from one test cannot be ranked directly against an area-normalized rate from another. The units describe different quantities. First establish the method and sample history; then decide whether the results answer the same engineering question.
Understand what a screening method establishes
ASTM E595 addresses total mass loss and collected volatile condensable material in a vacuum environment. NASA's published compilation applies this type of evidence to spacecraft-material selection. That context matters: a listed material result is not qualification of a different compound, a finished seal or an optical assembly.
If your project specifies an outgassing method, request its applicable edition and acceptance criteria. If it does not, define the contamination concern with the equipment owner before asking suppliers for a generic “low-outgassing” declaration. Keep the method's output separate from the equipment's functional approval.
Keep sample treatment visible
Record whether the sample was tested as supplied, after post-curing, after cleaning, after a bake-out or after another conditioning step. Identify the actual compound, lot and specimen geometry. Record storage and packaging history where they form part of the agreed preparation.
When comparing samples, use the same preparation basis or explain the difference. A result obtained after a defined treatment describes that sample state. Agree whether the production delivery will have that same state and which records are required to identify it.
Do not infer a universal post-curing or bake-out schedule from an unrelated material result. The proposed process, component dimensions and acceptance tests need to be reviewed together.
Separate outgassing, particles and sealing function
ISO 14644-1 classifies air cleanliness by airborne-particle concentration. That classification is a different measurement from a seal's release of volatile material. Ask for the evidence relevant to each requirement rather than using an air-cleanliness class as an outgassing certificate.
Keep assembly leakage and any gas-permeation requirement separately identified as well. A successful contamination screen does not establish the installed joint's leakage result. Conversely, a joint that passes a specified leak check still needs the contamination evaluation required by the equipment.
Build the comparison around your equipment
Share the seal and mating-part drawings, compound reference, vacuum and temperature cycle, contacting process media and any cleaning sequence. Identify which surfaces or functions are contamination-sensitive, what test results are required and who approves the equipment trial.
For a replacement, include the original part identification and the observed reason for the change. Keep fit, material evidence and equipment validation as separate approval questions. Review FFKM replacement requirements if that is the procurement route.
Send RubberQ the application and reporting requirements to discuss the candidate material and sample scope. The testing page provides a starting point for agreeing methods and records; the final evaluation should address the actual equipment conditions.