Inline leak test vs vacuum chamber: which catches more defects?

How they compare (practical for carts/disposables)

In-line dry air: pressure-decay / mass-flow

Sensitivity: Detects small leaks down to the low 10⁻⁴–10⁻³ mbar·L/s class (setup-dependent); mass-flow is less affected by thermal transients than simple pressure-decay. Best for micro-leaks + 100% screening.
cdn.thomasnet.com
+1

Pros: Fast, automatable, dry/clean (no water near hardware).

Cons: Finds “pass/fail” but not the exact leak location.
atequsa.com

Vacuum chamber (underwater) bubble test — ASTM D3078

Sensitivity: Geared to gross leaks; visual bubbles under vacuum. Good as a locator test or for flexible packs, but misses micro-leaks that air/mass-flow can catch. Risk of water ingress on finished devices.
ASTM International | ASTM
+1

Pros: Shows where the leak is; simple to run.

Cons: Destructive/wet, slower, limited micro-leak detection vs air tests.
Applus+ Keystone

Vacuum-decay chamber (dry) — ASTM F2338

Sensitivity: Higher than bubble tests and non-destructive; measures vacuum loss in an evacuated chamber. Can address partially plugged leaks by evacuating below the liquid’s vapor pressure. Often used for sampling or with dedicated automation.
ASTM International | ASTM
+1

Helium MS (tracer-gas)

Sensitivity: Orders of magnitude better (down to ~10⁻¹¹–10⁻¹² atm·cc/s in ideal rigs). Used for engineering builds, failure analysis, or tight R&D limits—not typical for every unit in production.
agilent.com
+1

Recommendation for vape lines

Primary gate (100% on line): Dry pressure-decay or mass-flow at sub-assembly/final assembly to catch micro-leaks quickly. This maximizes real defect capture per shift.
intertechdevelopment.com
+1

Secondary (AQL or lot-release): Dry vacuum-decay (ASTM F2338) sampling for tighter sensitivity on sealed SKUs with small headspace.
ASTM International | ASTM

Locator/troubleshooting: Bubble test (ASTM D3078) to visually find leak paths on suspect lots or packaging only. Avoid on oil-filled devices to prevent contamination.
ASTM International | ASTM

R&D/FA: Helium MS when you need to characterize very small leak limits or correlate to field failures.
agilent.com

Bottom line: If “vacuum chamber” = underwater bubble test, in-line dry air (pressure-decay/mass-flow) catches more defects in day-to-day vape production because it’s both more sensitive to small leaks and applicable to 100% of units. If “vacuum chamber” = dry vacuum-decay, it’s more sensitive than bubble and competitive with (often better than) basic pressure-decay for small packages—but throughput and cost usually make it a sampling or specialized in-line station, not your only gate.