Fire suppression technology continues to evolve, with both single and dual agent systems offering effective solutions for heavy equipment protection. While single-agent liquid systems have seen advancements, dual agent systems remain a critical option for comprehensive fire protection. This article aims to provide a clear understanding of how dual agent systems function and why they remain a vital choice for fire suppression.
Note: AFEX provides both dual and single-agent systems. Our interest is not in promoting one option over the other but in delivering the most effective fire suppression system tailored to safeguard operators and address specific fire hazards—whether the system utilizes a single or dual agent.
Understanding Dual Agent Design
Dual agent systems are designed to strategically deploy dry and liquid agents to target different hazards on the same piece of equipment:
- Dry chemical agent rapidly knocks down flames and is highly effective at combating three-dimensional fires by flooding a volume of space, such as an engine compartment, while also allowing for precise application where needed.
- Liquid agent provides both suppression and cooling by rapidly reducing heat on hot surfaces to prevent reflash and address hazards like superheated turbochargers or manifolds. Liquid agent is used for local applications.
By combining the strengths of both agents, dual agent systems offer comprehensive coverage tailored to the specific fire risks identified during a Fire Risk Assessment. Depending on the fire hazards present, this combined approach may provide superior protection compared to relying solely on a single agent.
Addressing the Myth: Is Dry Chemical Outdated?
A common misconception is that dry chemical agent is antiquated or less effective. However, real-world applications demonstrate otherwise. ABC powder agent has well-documented advantages, including: 
- Effective suppression of three-dimensional fires
- The ability to penetrate hidden fire areas due to its dispersal properties—dry agent can navigate around obstructions like hydraulic hoses, ensuring more complete fire suppression coverage
- Greater agent coverage per nozzle compared to liquid agent nozzles, which is particularly beneficial for larger vehicles
- Reliability in freezing conditions where liquid agents may face performance challenges
While liquid agent has excellent cooling properties, different tests highlight that dry chemical agent can be more effective in certain scenarios. A well-rounded fire suppression strategy should consider multiple test conditions and application-specific needs.
Installation and Cleanup Considerations
Some concerns exist around the complexity of dual agent systems in terms of installation, actuation, and cleanup. Let’s examine these points:
Installation
Mounting dry and liquid agent tanks side-by-side is no more difficult than installing multiple tanks of the same agent type. Achieving equivalent coverage with liquid agent alone may require additional tanks, reinforcing the importance of a balanced approach.
Actuation
Dual agent systems function as a single integrated solution. Modern designs ensure simultaneous actuation, making operation comparable to single-agent systems.
Cleanup
Both dry chemical and liquid agents leave some residue after discharge. However, when weighed against the potential loss of equipment or operational downtime due to a fire, cleanup is a minor consideration.
The Importance of a Comprehensive Fire Risk Assessment
A robust Fire Risk Assessment considers all potential hazards on a machine. While hot surfaces like turbochargers and manifolds are significant ignition points, other key risks include:
- Hydraulic fluid sprays
- Hydraulic pumps and filters
- Battery compartments
- Electrical hazards (e.g., starters and alternators)
- Fuel filters
- Haul truck generators
- Fires in hard-to-reach or enclosed areas
A well-conducted Fire Risk Assessment ensures the most effective suppression strategy is selected, which often includes a dual agent system to provide complete protection.
Meeting Industry Standards
Both FM Approvals and NFPA standards recognize and validate the effectiveness of both single and dual agent systems. Dry chemical agent has passed stringent FM testing, demonstrating its capability to suppress fires in complex scenarios.
Additionally, NFPA standards require dual agent systems for equipment with hydraulic lines exceeding 150 gallons. This applies to large machines such as 250-ton haul trucks, 20-cubic-yard excavators, and 30-cubic-yard bucket wheel loaders. These regulations highlight the necessity of dual agent systems in specific applications where fire hazards demand comprehensive suppression strategies.
Why Dual Agent Systems Remain an Essential Option
- Tailored Protection: Fire suppression is not one-size-fits-all. Machines have different types of hazards – dry powder is better suited for some, while liquid agent is more effective for others. Dual agent systems allow for customized protection, ensuring the right agent is applied to the appropriate hazard.
- Performance in Extreme Conditions: Dual agent systems are particularly effective in extreme environments, such as low temperatures where liquid agents alone may struggle.
- Proven Track Record: Dual agent systems have been widely adopted over the last two decades and have demonstrated their effectiveness in protecting ultra- and mega-class mining vehicles.
- Regulatory Recommendations: The NFPA specifically recommends dual agent systems for equipment with hydraulic lines exceeding 150 gallons, reinforcing their importance in high-risk applications. This is outlined in NFPA Standard 120, Chapter 5.3.8.3.3 and Standard 122, Chapter 12.3.8.3.3.
Conclusion
Advancements in single-agent liquid fire suppression systems are valuable, but they do not eliminate the need for dry powder or dual agent systems. Selecting the right fire suppression solution should be based on a thorough Fire Risk Assessment rather than generalizations about agent effectiveness.
AFEX is committed to protecting what matters most by offering a full range of fire suppression solutions - whether single or dual agent - ensuring each system is tailored to the needs of the equipment and environment. When used as intended, dual agent systems continue to provide an essential layer of fire protection for industries that rely on heavy-duty equipment.
