Consider a large e-commerce distribution centre: 11 m storage height and genuinely mixed commodity — Class 3 timber furniture alongside boxed plastic electronics and textiles. NFPA 13 produces one design, EN 12845-2 a second and FM Global DS 8-9 a third. When the insurer makes FM compliance a condition of cover, the scheme typically moves to ESFR with a high K-factor. This guide brings the three standards together into practical decisions for logistics warehouse fire protection.
First Step — Commodity Classification (FM DS 8-1 + NFPA 13)
- Class 1: noncombustible products on combustible pallets (glass, metal)
- Class 2: noncombustible products in heavy corrugated cartons (canned goods)
- Class 3: combustible products such as timber furniture, paper and textiles
- Class 4: Class 3 commodity with a limited proportion of plastics
- Group A plastics: plastic containers and toys — most modern e-commerce stock falls here
Storage Height — The Governing Parameter
| Storage height | Typical design approach |
|---|---|
| Up to 3.7 m | Ceiling-only sprinklers are generally adequate (Class 1–3) |
| 3.7–7.6 m | CMSA or ESFR (Class 3–4) |
| 7.6–12.2 m | ESFR, with in-rack sprinklers for plastics |
| Above 12.2 m | ESFR plus in-rack sprinklers and fire wall zone separation |
ESFR vs CMSA — Which One?
| Criterion | ESFR | CMSA |
|---|---|---|
| Objective | Suppression | Control |
| K-factor range | K200–K480 | K115–K240 |
| Operating pressure | Higher (typically 3.5–5.2 bar) | Lower (typically 2–4 bar) |
| Design sprinkler count | 12 | 15–30 |
| Roof slope tolerance | Restrictive | More tolerant |
| In-rack sprinklers | Often avoided (ceiling-only) | Frequently required |
| Maintenance | Simpler | Harder (in-rack pipework) |
| Obstruction sensitivity | High | Moderate |
Most new logistics warehouses favour ESFR: a cleaner roof, less in-rack pipework to maintain and, frequently, a better insurance position.
Water Supply and Tank Capacity
- An ESFR ceiling design at high storage produces a substantial simultaneous demand, typically several thousand litres per minute for 60 minutes
- Hose stream allowance must be added on top of the sprinkler demand for the same duration
- Town mains alone are rarely sufficient — an on-site tank with duty and standby fire pumps is the norm
- FM Global DS 3-2: tanks must be protected against freezing, which matters in inland Turkish climates
Flue Space — The Most Common Site Violation
- Transverse flue: the vertical gap running across the rack, typically 150 mm minimum
- Longitudinal flue: the gap between back-to-back rack rows, typically 75 mm minimum
- Typical violation: cartons overhang the rack edge and close the flue, so sprinkler water cannot penetrate down into the storage array
- Insurance surveys: flue obstruction is one of the most frequently raised recommendations at annual survey
- Practical fix: operator training, painted rack limit markings and routine spot checks
Practical Notes for Turkish Projects
- Large e-commerce and grocery distribution centres commonly design to ESFR with high K-factor heads
- Automated storage and retrieval (ASRS) installations bring FM Global DS 8-34 into play alongside NFPA 13
- International logistics operators generally impose FM compliance through their own group standards
- Where FM is not required, BS EN 12845-2 and the Turkish fire regulation set the baseline
Quick Checklist
- Commodity class correctly assigned, including plastics content
- Storage height based on actual use plus a realistic future projection
- ESFR vs CMSA decision agreed with the insurer and the budget owner
- Tank capacity covers sprinkler demand plus hose stream for the full duration
- Flue spaces maintained: transverse and longitudinal minimums respected
- FM DS 8-1 / DS 8-9, EN 12845-2 and NFPA 13 reviewed in parallel
- Insurer requirements clarified at the very start of design, not at handover
Frequently Asked Questions
What is the difference between ESFR and CMSA sprinklers?
ESFR (Early Suppression Fast Response) aims to suppress the fire outright with a small number of high-flow heads operating quickly, and is normally designed as ceiling-only. CMSA (Control Mode Specific Application) aims to control the fire rather than extinguish it, uses lower pressures and a larger number of operating heads, and usually needs in-rack sprinklers for tall storage.
Why is flue space so important in rack storage?
Flue spaces are the vertical channels that let sprinkler water travel down into the storage array and let hot gases rise to operate the ceiling heads. If cartons overhang and block the flues, water is deflected across the top of the load and never reaches the seat of the fire, so a fully compliant sprinkler system can still fail in practice.
Does ESFR always remove the need for in-rack sprinklers?
No. ESFR is designed as a ceiling-only solution within defined limits of storage height, roof height, commodity class and rack configuration. Beyond those limits — particularly with Group A plastics at high storage — in-rack sprinklers are still required, and the applicable standard's tables must be checked rather than assumed.
Why do insurers ask for FM Global compliance when the local code is satisfied?
National fire regulation sets a life safety baseline, whereas FM Global datasheets are written around property loss prevention and business interruption. An insurer carrying the property risk therefore applies its own, generally more demanding, criteria. Compliance is contractual rather than legal, but it directly affects premium and cover.
How is warehouse fire water tank capacity determined?
Capacity is the sprinkler design demand plus the hose stream allowance, multiplied by the required duration. The sprinkler demand comes from the design density or the number of operating heads at their design pressure, so the storage arrangement drives the tank size much more than the building floor area does.
What happens if storage height increases after the system is installed?
The design becomes invalid. Storage height is the single most influential parameter in warehouse sprinkler design, so raising the stack, adding a rack level or changing to a more hazardous commodity can push the installation outside the standard it was designed to. Any such change requires the hydraulic design to be reassessed.
SprinkCalc — Fire Sprinkler Design Across Three Standards
SprinkCalc covers hazard classification, design density and area, K-factor selection, water demand and hydraulic calculations for NFPA 13, FM Global and BS EN 12845 in a single iOS app, and exports a professional PDF report.
Download SprinkCalc on the App Store
MEP Calc — 86+ Engineering Calculators
MEP Calc bundles 86+ engineering modules in one iOS app: 21 fire calculations plus heating, cooling, HVAC, plumbing, steam and natural gas.
Download MEP Calc on the App StoreNFPA: 13 (Standard for the Installation of Sprinkler Systems — storage chapters). EN: BS EN 12845-1 and BS EN 12845-2 (CMSA and ESFR). FM Global Property Loss Prevention Data Sheets: DS 8-1 (Commodity Classification), DS 8-9 (Storage of Class 1, 2, 3, 4 and Plastic Commodities), DS 8-34 (ASRS), DS 3-2 (Water Tanks), DS 3-7 (Fire Protection Pumps), DS 2-1 (Corrosion). Turkiye: Fire Regulation (BYKHY); TS EN 12845.