gastightness

Gastightness, or gastightness, is the property of a container, structure, or system to prevent the passage of gas through its boundaries. It is important for safety, containment of hazardous or pressurized gases, energy efficiency, process control, and product quality. Gastightness can apply to buildings, pressure vessels, piping, vacuum systems, and packaging.

Testing and measurement of gastightness depend on the required sensitivity and operating conditions. Common techniques include pressure decay or constant-pressure tests to measure leak rate; bubble testing with a soapy solution for quick checks; tracer gas methods using helium or sulfur hexafluoride with a dedicated leak detector; and vacuum decay or mass-spectrometry-based leak detection for high-sensitivity needs. In buildings and other large enclosures, gastightness is typically assessed with a blower door test that pressurizes or depressurizes the space to a standard differential, reporting an air leakage rate (commonly ACH50) or equivalent metrics.

Factors affecting gastightness include material porosity, the quality of seals and joints, manufacturing tolerances, installation workmanship, temperature, and long-term aging. Proper design and maintenance of seals, gaskets, welds, and fittings are essential to preserve gastightness over time. Changes in pressure differences, movement, or thermal cycling can alter leakage paths and performance.

Standards and terminology vary by application. Building codes and testing standards specify acceptable airtightness levels and procedures; vacuum and pressure vessel standards define allowable leak rates and testing protocols; and packaging, aerospace, and chemical industries use specialized methods to assess barrier properties and short-term leakage.