Filter pressure drop warning on HMI · Open Face
Filter pressure drop warning on HMI on Open Face booths
The pressure-drop warning on an open-face HMI is the simplest version of this alarm across booth types, the open-face geometry typically has only one monitored filter position (rear-wall exhaust), so alarm-source identification is immediate. The fix is replacing the rear-wall pads. Some open-face installations with powered AMU also monitor the AMU pre-filter; the HMI will label the alarming sensor in those cases. Open-face HMI installations are less common than on closed booths because many open-face decks ship without HMI monitoring at all, if you have an alarm, you have a system that will tell you exactly when to swap.
Quick answer
A pressure-drop warning on an open-face booth's HMI almost always points at the rear-wall exhaust pads, that's the only continuous filter stage in the airflow path on most open-face installations (no front intake filter, often no AMU pre-filter). Replace the rear-wall pads; the alarm clears. Persistent alarm on fresh media indicates sensor calibration drift or fan-side imbalance, professional service from there.
Diagnostic logic for Filter pressure drop warning on HMI on Open Face
Open-face sensor map. Differential-pressure sensors on open-face installations: - Rear-wall exhaust sensor, measures delta-P across the paper-mesh, accordion-paper, or pocketed-paper pads in the rear-wall bank. Primary alarm source. - AMU pre-filter sensor (where present), only on open-face installations that include a powered make-up air supply, which is the minority. Many open-face booths run on ambient shop draw without AMU. - Specialty-stage sensor (where present), open-face booths designed for VOC compliance may include a downstream carbon polish stage with its own sensor.
Alarm-source mapping to media replacement. The 25-entry filter media taxonomy on this site (12 exhaust + 9 intake + 4 specialty) covers the rear-wall exhaust positions and any specialty stages on open-face installations. The verified-fitment kit names the specific media-type slug.
Cycle math reminder. Open-face rear-wall pads at 7-21 day cycle, fastest cycle of any booth type because there's no intake-side filter to capture larger particulate before it hits the exhaust. AMU pre-filter (where present) at 60-90 day cycle.
Regulatory landscape
Open-face booths face the strictest face-velocity scrutiny because the open intake is the containment boundary. A pressure-drop alarm signals that airflow is dropping; if face velocity also drops below the OSHA / NESHAP / AQMD specification, you've crossed into compliance violation territory. Filter-replacement records dated against alarm events are the maintenance log inspectors expect; subscription delivery covers the documentation by default.
Filter pressure drop warning on HMI on Open Face FAQs
My open-face HMI doesn't differentiate which sensor fired — what do I do?
Replace the rear-wall pads first. On most open-face installations that's the only monitored position. If the alarm doesn't clear, then check whether you have an AMU pre-filter sensor (less common) and replace that.
How fast do open-face rear-wall pads load relative to other booth types?
Faster than crossdraft, downdraft, or semi-downdraft equivalents at the same throughput — no intake-side filter means no first-stage capture, so all the overspray hits the rear-wall pads directly. 7-21 day cycle is typical; high-throughput shops run shorter.
What if my open-face doesn't have an HMI?
Many open-face booths don't. Cycle-based subscription substitutes for the alarm — fresh media arrives on calibrated interval based on your spray volume.
What if the alarm fires immediately on fresh pads?
Sensor calibration drift, sensor port obstruction, wrong filter installed, or fan over-speed. Professional service handles all four.
My open-face is a Col-Met / Global / Spray Tech — does the booth-make change this?
No. The alarm logic and replacement order is the same across open-face makes. Specific media-type slugs vary by manufacturer; the verified-fitment kit handles naming.
Can I just clear the alarm and keep spraying?
Don't. The alarm means airflow is below design. On an open-face booth, that almost always means face velocity is below spec — which is an immediate OSHA and AQMD compliance issue. Replace the pads.
Sources
Primary references cited on this page.
- OSHA 29 CFR 1910.107 — Spray Finishinghttps://www.osha.gov/laws-regs/regulations/standardnumber/1910/1910.107
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