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Understanding Free Available Chlorine (FAC): The Key to Measuring HOCl Power

HOCl works because of one key metric: Free Available Chlorine (FAC). Learn how to measure it, what your ppm levels mean, and how to dial in the perfect HOCl concentration for food, health, and industrial use.

November 17, 2025 · 2 min read

A note on claims

EcoloxTech generators are regulated by the EPA as devices, are not registered disinfectants, and we make no efficacy claims for them or for the solution they produce. The only EcoloxTech product with disinfection claims is HOCl-AS200 (EPA Reg. No. 101112-1), used according to its label. What applies where is set out on our regulations page and in staying compliant with HOCl. Research referred to describes published studies under their own test conditions and is not a claim for any product.

HOCl Kill Power: Understanding Free Available Chlorine (FAC)

 

HOCl is powerful—but how do you measure that power? It all comes down to one metric: Free Available Chlorine, or FAC. This is the active disinfecting ingredient in your hypochlorous acid solution—and it determines how strong your kill power really is.

 

Understanding FAC gives you control over:

  • 💧 Disinfection strength
  • ⚖️ Regulatory compliance
  • 📉 Chemical safety
  • 🔬 System efficiency

What Is FAC?

Efficacy claims belong to registered products used according to their labels: EcoloxTech generators are EPA-regulated devices and carry none, and the only EcoloxTech product with disinfection claims is HOCl-AS200, EPA Reg. No. 101112-1. It’s measured in ppm (parts per million) and fluctuates depending on:

  • 🔄 Flow rate
  • ⚡ Amperage
  • 🧂 Additive type (salt + vinegar or HCl)
  • 📉 pH level

The Perfect Range by Use Case

Use Case FAC (ppm) Notes
Hands / Skin 20–60 ppm Gentle, pH-neutral
Produce / Food Surfaces 50–100 ppm Whether a rinse or drain step is required depends on the applicable rule and the product used; the limits are set out on our regulations page.
Tools / Floors 100–200 ppm Spray or mop
Medical / Outbreak Control 200–400 ppm High-kill, fast acting

 

EcoloxTech generators can produce up to 400 ppm FAC using Formula 3 (HCl) on the E-1200.

How to Measure FAC

You can easily measure FAC using:

  • Chlorine Test Strips
    Measures 10, 50, 100, 200 ppm

  • Chlorine Photometer
    Digital ppm measurement

Just dip and match—or scan the reading for ultra-precise ppm control.

How to Adjust Your HOCl System for Target FAC

EcoloxTech systems give you real-time control of FAC levels using three adjustable variables:

Setting Increases FAC When…
Ampere (A) You raise it (more electrical current = stronger HOCl)
Pump Speed (PS) You lower it (more concentrated brine enters cell)
Flow Rate (L/min) You lower it (longer reaction time = more chlorine)

 

Example (E-1200 at 22A):

  • 1 L/min = ~278 ppm FAC
  • 6 L/min = ~108 ppm FAC

pH and FAC: The Hidden Connection

HOCl is most active when pH is 5–6. Above pH 7, HOCl begins converting to hypochlorite (OCl⁻), which is less effective and more corrosive. You can maintain ideal pH by:

  • Using Formula 2 or 3 in your additive tank (vinegar or HCl)
  • Installing an EcoloxTech pH dosing system for automatic control

Optimize Your Kill Power

Knowing your FAC = knowing your sanitizing strength. With EcoloxTech:

  • You can test it.
  • You can control it.
  • You can trust it.


Written by the EcoloxTech engineering team. If you want this applied to your own facility, the free sanitation audit sizes the system and models the payback in writing, at no charge.

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