Glove Box Leak Rate: Simple Targets and a 5-Minute Test

What is leak rate?

In simple words:

Leak rate = pressure loss over time × box volume.

Unit: mbar·L/s

Example:

• 1000 L box
• Pressure drops from 5 mbar → 4 mbar in 1000 s

Leak rate = (1 mbar × 1000 L) / 1000 s = 1 mbar·L/s → too high.
You want numbers much smaller than that.

What is “good enough”?

Typical practical targets：

If you are better than 1×10⁻² mbar·L/s and still suffering, look at transfers / solvents / purifier first.

Simple pressure-decay test (positive-pressure box)

You need：

• A pressure gauge (resolution 0.1 mbar or better)
• Chamber volume V (L)

Steps：

1. Seal the box
   • Close antechambers, valves, feedthroughs.
   • Stop external gas and pumps.
2. Pressurize & stabilize
   • Set box to about +5 mbar over ambient.
   • Wait 10 min for temperature to settle.
3. Isolate & start timing
   • Isolate from gas and pumps.
   • Record start pressure P₁ and time t₁.
4. Wait
   • Do not touch gloves or doors.
   • Wait 30–60 min.
5. Read again
   • Record P₂ and t₂.
6. Calculate leak rate
   • ΔP = P₁ – P₂ (mbar)
   • Δt = t₂ – t₁ (s)
   • Leak rate = (ΔP × V) / Δt (mbar·L/s)

Leak rate is OK, but ppm is bad?

Very common情况：

• Leak test：good
• O₂ / dew point：bad

常见原因：

• Bad transfers
  • Only one pump-down in the antechamber
  • No pressure equalization before opening inner door
• Solvent vapor
  • Open beakers, solvent-soaked wipes left inside
  • Dew point climbs but O₂ looks fine
• Purifier issues
  • No proper regeneration
  • Media exhausted or solvent-poisoned