Quick Response Fire Sprinkler

A quick response (QR) sprinkler has an RTI ≤50 (m·s)½, meaning it activates significantly faster than a standard response sprinkler at the same heat exposure. The key is the 3mm glass bulb — its smaller diameter gives it less thermal mass, so it heats up and bursts more rapidly in a fire plume.

Importantly, QR does not mean the sprinkler is more sensitive to accidental activation — the activation temperature (e.g. 68°C) is the same as a standard response model with the same colour bulb. QR simply activates faster once the rated temperature is reached.

Not always — it depends on the application. For life-safety occupancies (hotels, hospitals, residences, offices), QR is superior because earlier activation limits fire growth during the critical evacuation window. NFPA 13 mandates QR for these occupancies.

For high-challenge fire scenarios in high-piled or racked storage, standard response is generally preferred. Faster activation in a large open bay can mean more sprinklers opening simultaneously — potentially overwhelming the water supply before the fire is controlled. SR's slower, more deliberate activation opens fewer heads and maintains adequate pressure at each one, making suppression more effective. For storage-specific solutions, see our ESFR Fire Sprinkler page.

In CA-FIRE's range, QR models are identified by:

1. Model code prefix "K-" — e.g. K-ZSTX, K-ZSTZ, K-ZSTBS
2. "Q3" or "J" suffix — Q3 for concealed (ZSTDY), J for pendent/upright/sidewall models
3. 3mm glass bulb — visibly thinner than the 5mm bulb on standard response heads
4. Submittal tag / installation record — always verify from project documentation

Never rely on visual identification alone when replacing sprinklers on an existing system — always match the exact model code from the original installation record.

Generally no — NFPA 13 Section 6.2.4 and GB 50084 prohibit mixing QR and SR sprinklers in the same compartment or fire area in most cases. The reason is hydraulic: a QR head activates earlier, while nearby SR heads are still closed. If they are on the same branch line, the already-open QR head may divert flow away from the SR heads when they eventually activate, compromising overall system performance.

Exceptions exist — consult your system designer and refer to NFPA 13 for specific permitted scenarios. CA-FIRE can provide project-specific technical support for mixed-occupancy buildings.

All three are CA-FIRE quick response sprinklers with RTI ≤50 — the difference is installation orientation:

K-ZSTX — Pendent (下垂). Hangs downward from branch pipe below the ceiling. Most common QR type globally.
K-ZSTZ — Upright (直立). Mounts above the branch pipe, deflector facing up. For exposed-pipe and dry-pipe systems.
K-ZSTBS — Sidewall (边墙). Wall-mounted near ceiling level, no ceiling pipe needed. For corridors and hotel rooms.

Deflectors are not interchangeable between types — always install the correct orientation for your pipe routing.

The minimum design pressure at the sprinkler is 0.10 MPa (1 bar / 14.5 psi) for all K5.6 (K80) and K8.0 (K115) QR models. At 0.10 MPa, a K5.6 head flows approximately 80 L/min and a K8.0 head flows approximately 115 L/min.

Maximum working pressure is 1.2 MPa for standard glass bulb models. Hydraulic calculations should be performed by a qualified fire protection engineer to verify pressure requirements at the most hydraulically demanding sprinkler in the system.