Inside the Marioff HI-FOG® Industrial System
By Duncan Winsbury
Author of Fire Protection Systems
Introduction
The Marioff HI-FOG® system represents one of the most advanced developments in active fire suppression — a high-pressure water mist technology engineered for complex and high-value risks where conventional sprinklers may not offer the precision, cleanliness, or efficiency required.
This article explores how the HI-FOG system works, its technical components, the fire science behind it, and why it is increasingly used across industrial, marine, and energy sectors.
1. The Principle Behind HI-FOG
HI-FOG operates on the principle that smaller water droplets suppress fire more effectively than large ones.
At discharge pressures between 35 bar and 140 bar, the system produces droplets typically between 50 and 100 micrometres in diameter — fine enough to remain suspended in the air and penetrate the flame zone.
These droplets:
- Absorb heat rapidly, cooling both flames and hot gases.
- Reduce radiant heat, limiting fire spread.
- Displace oxygen locally as they vaporise, helping to smother combustion.
The result is a system that can suppress or extinguish fire using a fraction of the water flow required by sprinklers, typically 70–90 % less.
2. System Configuration
HI-FOG is available in several configurations to suit building types and operational needs:
| System Type | Description | Common Applications |
| Wet Pipe | Pipes pre-filled with pressurised water; immediate discharge when a head opens. | Accommodation areas, control rooms. |
| Pre-Action | Pipes dry until confirmed fire detection signal activates valves. | Data centres, turbines, archives. |
| Deluge | All nozzles open simultaneously when triggered. | Machinery spaces, conveyors, engine enclosures. |
Each configuration uses precision-engineered stainless steel components and fine mesh strainers to prevent nozzle blockage.
3. Key Components and Operation
a. Pump Unit (MT4 or Modular Skid Units)
- Generates pressures up to 140 bar.
- Uses stainless steel piping and filtration systems to maintain water purity.
- Often supplied as a compact skid assembly, simplifying installation.
b. Distribution Network
- High-pressure stainless steel tubing (typically 12–36 mm OD).
- Section valves, flow sensors, and isolation zones for local activation.
c. Spray Heads / Nozzles
- Each nozzle incorporates micro-orifices (≈ 300 µm) producing a fine mist cone.
- Nozzles may include thermal bulbs (like sprinklers) or remain open for deluge use.
d. Detection and Control System
- Interfaces with heat/smoke detectors, releasing valves and pump start circuits.
- Enables pre-action or zoned activation for targeted suppression.
e. Water Supply
- Can operate from a dedicated tank or mains.
- Requires filtered, non-corrosive water (chlorides < 50 ppm; solids < 100 µm).
4. Performance and Fire Tests
HI-FOG has undergone extensive full-scale fire testing to validate its performance under different hazards:
| Test Standard | Scope / Application | Outcome |
| IMO MSC/Circ. 1165 | Machinery spaces, engine rooms | Type-approved for Class 1–3 enclosures. |
| BS 8489-1 Annex F | Industrial / commercial applications | Equivalent to Ordinary Hazard Group 3 (OH3) by test evidence. |
| FM 5560 / UL 2167 | Industrial, turbine, and electrical rooms | Approved for gas turbines, cookers, switchrooms. |
These tests confirm the system’s capability to control Class A (solid), Class B (liquid), and electrical fires, provided it is applied within its tested configuration limits.
5. Typical Industrial Applications
HI-FOG is widely deployed across industries where rapid fire suppression and low water damage are critical:
| Sector | Example Applications |
| Power & Energy | Gas turbines, generator enclosures, transformer rooms. |
| Manufacturing | Conveyor tunnels, metal processing, packaging lines. |
| Food Industry | Industrial fryers and oil cookers (FM-approved systems). |
| Marine / Offshore | Engine rooms, pump rooms, accommodation spaces. |
| Heritage & Culture | Archives, galleries, listed buildings (minimal damage). |
In each case, the system’s compact design and fine droplet distribution make it ideal for confined or ventilation-controlled spaces.
6. Advantages over Conventional Sprinklers
| Feature | Sprinkler System | HI-FOG Water Mist |
| Water use | High (L/min/m²) | Very low (70–90 % reduction) |
| Fire damage | Greater water runoff | Minimal collateral damage |
| Activation time | Thermal bulb response | Fast detection-linked activation |
| Installation footprint | Large pipes and tanks | Compact stainless network |
| Suitability for electrical / oil fires | Limited | Certified for tested hazards |
| Re-entry time | Delayed | Quicker due to less smoke and steam |
HI-FOG is especially effective in critical facilities where downtime or water contamination would be costly — such as data centres or manufacturing cleanrooms.
7. Limitations and Design Considerations
While the system’s benefits are significant, successful implementation depends on correct application:
- Water quality control is vital; poor filtration can block nozzles.
- Cost and complexity are higher than sprinklers due to pumps, valves, and testing requirements.
- Ventilation management is necessary during activation to retain mist concentration.
- Approval depends on test evidence for each specific hazard and compartment geometry.
Routine maintenance and flushing must be incorporated into building management plans to maintain performance integrity.
8. Integration with Performance-Based Fire Design
HI-FOG’s flexibility aligns perfectly with the performance-based building design philosophy.
Rather than applying prescriptive flow densities, engineers model the thermal and fluid dynamics of the mist discharge to demonstrate that ASET (Available Safe Egress Time) exceeds RSET (Required Safe Egress Time).
When integrated with CFD and evacuation models, HI-FOG systems can form part of an optimised, multi-layered fire strategy — combining active suppression, smoke control, and structural fire resistance to achieve defined safety objectives.
Conclusion
The Marioff HI-FOG system is not simply a smaller version of sprinklers — it is a precision-engineered, high-pressure mist technology that embodies the shift towards performance-driven fire protection.
Its ability to suppress diverse fires with minimal water, protect sensitive assets, and adapt to complex risks makes it one of the most versatile tools in modern fire engineering.
As industries move toward sustainability and resilience, systems like HI-FOG demonstrate that innovation and reliability can coexist in the protection of life, property, and environment.
Further Reading
- BS 8489-1:2016 — Fixed firefighting systems: Industrial and commercial water mist systems.
- NFPA 750:2023 — Standard on Water Mist Fire Protection Systems.
- Marioff HI-FOG MT4 Data Sheet (LS0190).
- Marioff White Paper – Water Mist Fire Suppression (2021).
About the Author
Duncan Winsbury is a UK-based Fire Engineer and author of Fire Protection Systems, Performance-Based Building Design, and Principles of Fire Engineering – Science, Safety and Solutions.
His work focuses on bridging scientific theory with practical fire strategy implementation and promoting safer, performance-led design in the built environment.
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