Sphere Pressure Differential
VC-MET-402 — the negative pressure held inside containment spheres relative to the corridor — the primary inward-seal guarantee.
Definition
Sphere Pressure Differential is the gauge pressure inside a containment sphere relative to its corridor (Pa), held negative so air moves inward. It is the first physical guarantee that nothing escapes a sphere.
Why it matters
Negative differential is what keeps spores, pollen, and volatiles inside a sphere. Loss of vacuum is the earliest mechanical sign of a containment problem and gates every higher-grade specimen operation.
Formula
ΔP = P_sphere − P_corridor [Pa, gauge] Held negative by the extract loop; setpoint −35 Pa. Measured by differential transducers at two ports per sphere; the less-negative of the two governs alarming.
Inputs
| Input | Detail | Source |
|---|---|---|
| Differential transducer | Two ports per sphere | PhytoSense Mesh |
| Corridor reference | Corridor static pressure | PhytoSense Mesh |
| Extract loop | Setpoint −35 Pa | CHLORA |
Units & Scale
Pa gauge, integer (negative = inward). Less-negative-is-worse: thresholds fire as ΔP rises toward zero.
Sampling & Source
- Sampled every 10 seconds per sphere.
- Governed by the less-negative of two transducer ports.
- Loss of vacuum gates GCL-grade operations.
Thresholds
OK
WARN
CRIT
Recent Trend
Zone roll-up, last 14 sampling periods (current −34):
Interpretation Guidance
| Band | Reading | Likely Driver | Action |
|---|---|---|---|
| −45…−25 | Sealed | Normal extract | Standard operations. |
| −24…−18 | Soft | Extract drift or door cycle | Check extract loop. |
| −17…−5 | WARN | Seal degradation | Suspend open handling. |
| > −5 | CRIT | Vacuum lost | Breach procedure; isolate. |
Related Metrics
Containment Integrity Index
Composite this feeds.
VC-MET-403Seal Leak Rate
Mechanical leak partner.
VC-MET-408HEPA Filter Loading
Extract-path state.
VC-MET-406Airborne Spore Load
Escape consequence.
Related SOPs
- Emergency breach — SOP Library.
- Sphere integrity — SOP Library.