HEPA Filter Loading
VC-MET-408 — the loading of HEPA filtration stages as percent of pressure-drop budget — filter-life and bypass risk.
Definition
HEPA Filter Loading is the fraction of each HEPA stage's pressure-drop budget consumed (% ΔP), derived from across-filter differential pressure. It indicates remaining filter life and the risk of bypass or flow loss.
Why it matters
Loaded filters lose flow and, at the extreme, risk bypass that lets bioburden into corridors. Loading schedules filter changes before they constrain extract flow and undermine sphere differential.
Formula
Load = (ΔP_now − ΔP_clean) / (ΔP_max − ΔP_clean) × 100
[% of budget]
ΔP measured across each stage; the most-loaded stage in a
train governs. 100 % = change-out threshold.
Inputs
| Input | Detail | Source |
|---|---|---|
| Stage ΔP | Across-filter differential | PhytoSense Mesh |
| Clean baseline | Commissioning ΔP | CHLORA |
| Flow | Train volumetric flow | PhytoSense Mesh |
Units & Scale
% of ΔP budget, integer, governed by the most-loaded stage. Increasing-is-worse; upper thresholds apply.
Sampling & Source
- Sampled every 10 minutes across each stage.
- Most-loaded stage in a train governs.
- Schedules change-out before flow is constrained.
Thresholds
OK
WARN
CRIT
Recent Trend
Zone roll-up, last 14 sampling periods (current 42):
Interpretation Guidance
| Band | Reading | Likely Driver | Action |
|---|---|---|---|
| 0–60 | Healthy | Within service life | None. |
| 61–80 | Loading | Approaching service | Schedule change-out. |
| 81–95 | WARN | Constrained flow | Change-out; watch ΔP. |
| > 95 | CRIT | Bypass risk | Immediate change-out; isolate train. |
Related Metrics
Sphere Pressure Differential
Flow-dependent partner.
VC-MET-406Airborne Spore Load
Bypass consequence.
VC-MET-403Seal Leak Rate
Extract-path integrity.
VC-MET-311Sensor Mesh Coverage
Telemetry health.
Related SOPs
- Filter change-out — SOP Library.
- Facilities maintenance — Facilities.