A Caterpillar dozer with a dual agent fire suppression system installed. "Fire Suppression Agents: Are two really better than one?"

Are you researching fire suppression systems to protect your operators and mobile equipment? If so, you’re likely weighing the pros and cons of the different types of agents available in these systems, striving to select the one that will be most effective at fighting the types of fires associated with your application. While there are several types of agents offered, the two most popular for suppressing vehicle fires are dry powder and liquid chemical. But could the combination of these two really be the most effective? Are two agents better than one? 

Different Fire Sources Require Different Suppression Agents 

Mobile equipment fires can start at various locations around a machine, such as the transmission compartment or the exhaust. And these different locations often require a different agent for the most efficient suppression of the fire. When it comes to dry and liquid agents, their strengths lie in the following areas:

Dry Agent

AFEX Dry Chemical Fire Suppression System
  • Class A (debris), Class B (fuel), & Class C (electrical) 
  • Total flooding 
  • Fast fire knockdown
  • Wide coverage 
  • Non-conductive 

Liquid Agent

AFEX Liquid Chemical Fire Suppression System
  • Class A (debris) & Class B (fuel) 
  • Protecting surface areas 
  • Cooling hot surfaces 
  • Preventing reflash of pooled fuels 

For a fire that originates in an enclosed space, like an engine compartment, dry powder agent excels due to its ability to flood a volume of space, depositing a fine powder to smother flames. If liquid agent was used alone, it would take more time to suppress the fire and could potentially miss areas of the enclosure. 

What if the turbocharger catches fire? Liquid chemical agent would be the ideal choice due to its ability to target and cool hot surfaces quickly. Dry chemical applied to the same fire would take a bit longer to cool the hot metal in such a high-air flow environment. 

It’s clear that dry and liquid agents each possess unique qualities when it comes to suppressing fires across a vehicle. So, what if a fire suppression system combined these two agents, utilizing the best agent to target each fire hazard? 

Dual Agent: Combining Dry and Liquid Agent Benefits 

Schematic for Dual Agent Fire Suppression System

Dual agent systems, also known as “twin agents”, attack each fire source with the most effective agent. This allows the agent to both flood volumes of space while also targeting hot spots. Due to its effectiveness, the National Fire Protection Agency (NFPA, Chapter 120 – & Chapter 122 – actually requires dual agent fire suppression systems for large shovels exceeding 150 gallons of hydraulic fluids in their lines. 

Dry Agent

Floods Volume

Liquid Agent

Targets Hot Spots

Two Agents Working Together

Aside from its ability to perform better than dry or liquid agent systems alone, there are additional benefits of implementing a dual agent system, especially when compared to liquid-only systems. Some of these benefits include: 

  • More cost-effective solution 
  • Smaller footprint 
  • Adds less weight to the machine 

So, are two agents really better than one? Yes. Dual agent systems target fire hazards with the right agent to suppress a fire quickly, protecting your people, production, profits, and public image.

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