Quick Opening Device
The Dry-Pipe Trip Accelerator

Why QODs Exist — The Dry-Pipe Delay Problem

A dry pipe sprinkler system holds back 100+ psi of water pressure with 20–30 psi of air on a differential-pressure dry pipe valve (typically 5:1 or 6:1 ratio depending on manufacturer). When a sprinkler head opens during a fire, system air discharges through that one open sprinkler. The dry pipe valve cannot trip until enough air escapes to collapse the differential — and on a large system, that can take minutes.

Per Code Red Consultants Source 3: a well-maintained QOD can trip the dry pipe valve in under 4 seconds of sprinkler activation. Without a QOD on a large system, the same valve could take 2 to 4+ minutes. That delay means additional sprinklers activating, a growing fire, overwhelmed water supply, and the difference between a contained incident and total loss.

NFPA 13 §8.2.3.6 sets specific water delivery times for dry systems based on occupancy hazard — measured from the inspector's test opening to water discharge. The Quick Opening Device is how a system over 750 gallons actually meets those times.

When a QOD Is Required

Per NFPA 13 §8.2.3.6 thresholds Source 3:

Most dry systems in parking garages, cold storage warehouses, attics, loading docks, and unheated industrial spaces are large enough to require a QOD to meet NFPA 13 delivery times. Small systems (under 500 gallons) — like a residential attic dry system — typically don't.

Two Types — Accelerators vs Exhausters

Anatomy of a Mechanical Accelerator — Reliable Model B1

The Reliable Model B1 Accelerator with Integral Accelo-Check is the most common mechanical accelerator in the field. Here's what you're looking at when you encounter one on a dry pipe riser Source 5:

What the markings tell you: UL 703A is the specific UL listing category for “Quick-Opening Devices for Dry Pipe Valves.” The FM diamond confirms Factory Mutual approval. Both marks mean the device has been tested and listed for fire protection service — not just general industrial use.

Field tip: Record the serial number during inspections. When a mechanical accelerator starts false-tripping, the serial/date code tells you how old the unit is — and whether rebuilding or replacing with an electronic unit makes more economic sense.

Reset Procedure — From the Manufacturer's Label

The following 6-step reset procedure is printed directly on the Reliable Model B1 Accelerator label (photographed in the field). Every dry-system technician should know this sequence Source 5:

Step 3 is the one that trips up technicians who haven't worked on the B1 before — the Accelo-Check body and diaphragm must be physically removed and reinstalled to vent passageway “E.” Skipping this step leaves trapped air in the wrong chamber, and the accelerator won't set up properly. If you encounter a B1 that “won't reset,” check whether step 3 was performed.

Mechanical vs Electronic Accelerators

When a mechanical accelerator has caused repeated false trips on a facility, the cost of upgrading to an electronic unit is typically lower than a single false-trip water-damage claim. Cold-storage and mission-critical facilities increasingly spec electronic accelerators during new install or retrofit.

The Quarterly Test Nobody Remembers (NFPA 25 §13.4.5.2.4)

Test procedure (typical — verify against manufacturer IOM)

1. Notify the FACP and monitoring center that testing is in progress.
2. Shut off the main water supply to the dry pipe valve to prevent a real system trip during the test.
3. Simulate a pressure drop per the manufacturer's procedure (typically via the accelerator's test connection).
4. Verify QOD activation per the manufacturer's specification — the accelerator should trip within the rated time.
5. Reset the QOD per manufacturer instructions. For a Reliable B1, follow the 6-step reset procedure above — especially step 3 (vent the Accelo-Check).
6. Reopen the water supply and verify system pressure returns to normal.
7. Perform a main drain test (see Main Drain Test article) to confirm the water supply valve is fully open.
8. Reset alarms and notify the monitoring center that testing is complete.
9. Document the test in the facility ITM records — date, technician, pass/fail, any observations.

The #1 Field Problem — Shut Off & Forgotten

From Sprinkler Age, summarizing the most common QOD field finding Source 4:

The failure chain

1. Mechanical accelerator false-trips during normal operation (pressure wiggle, compressor cycle, ambient temperature swing).
2. System floods, fire department responds, facility has to drain and reset the wet dry system.
3. Maintenance closes the air supply valve feeding the accelerator to prevent another false trip.
4. They mean to come back and troubleshoot — but they don't.
5. Months or years later, the QOD is still out of service, the dry pipe valve still trips (just slowly), and the facility has no idea the problem exists.
6. During a real fire, the dry valve takes 2–4+ minutes to trip instead of seconds. Additional sprinklers activate. Fire grows uncontrolled.

Every dry pipe valve inspection must include verifying the QOD's air supply valve is OPEN. The fix for a chronic false-tripping mechanical accelerator is to troubleshoot the root cause or replace with an electronic unit — NOT to take the QOD out of service permanently.

DO NOT — The Cardinal Rules

NFPA 25 ITM Schedule

QOD on Inspection Reports

Inspection reports may list the QOD as a separate line item from the dry pipe valve itself. Common terminology variations: Quick Opening Device, QOD, Accelerator, Exhauster (on older systems). All refer to the same functional category. An inspector citing “QOD out of service” or “accelerator supply valve closed” is pointing at this device.

Typical QOD findings on reports: supply valve closed (the classic), not tested quarterly, trip time exceeds manufacturer spec, mechanical unit repeatedly false-tripping, reset procedure unknown to maintenance staff. For related content, see the Dry Pipe Valve article.