Will a Halogen Leak Detector Find R-32 & A2L Refrigerant Leaks?

You’re facing a new A2L refrigerant system, and you reach for your trusted old halogen leak detector. You wonder if it will even work, but the more important question is whether it’s safe to even try.

A standard halogen detector may weakly react to A2L refrigerants like R-32, but it is NOT the right or safe tool for the job. Its technology creates an internal spark, posing a serious ignition risk with these mildly flammable refrigerants. Using it is a dangerous gamble.

From my vantage point in the industry, I’ve watched the transition to A2L refrigerants with great interest. It’s a necessary step for the environment, but it introduces a new level of risk that every technician must respect: flammability. The tools we used for years on non-flammable refrigerants are not just becoming obsolete; some are becoming a liability. Understanding why your old leak detector is a hazard is the first step in protecting yourself, your customer, and their property.

What does a halogen leak detector actually detect?

To understand why this tool is wrong for A2L refrigerants, you first have to know how it works. You might think it sniffs out "Freon," but its mechanism is much more specific.

A halogen leak detector doesn’t detect refrigerant directly. It detects the presence of halogen gases—specifically chlorine and fluorine—by creating a high-voltage electrical field that these gases disrupt.

This technology is called corona discharge. Inside the sensor tip, a high voltage creates a stable plasma field between two electrodes. When the detector draws in air containing a halogenated gas (like the fluorine in R-410A or R-134a), these molecules disrupt the plasma. The machine detects this change in electrical current and sounds the alarm.

This is why it works on traditional refrigerants—they are all halogenated compounds. Since A2L refrigerants like R-32 are also HFCs (hydrofluorocarbons), they contain fluorine. So, in theory, a halogen detector might beep in the presence of a large leak. However, it’s often not sensitive enough to find the small, problematic leaks you’re actually looking for. But sensitivity isn’t the real problem. The real problem is the high-voltage spark it uses to do its job.

Is it safe to use a halogen detector on A2L refrigerants?

You know A2L means "mildly flammable." You also now know your halogen detector makes an electrical spark. The critical question is: can that small spark ignite these new refrigerants?

No, it is absolutely not safe. Using a standard halogen (corona discharge) leak detector on a flammable refrigerant is a serious safety risk. The internal high-voltage spark is a potent ignition source that can cause a fire or explosion.

This is the most important takeaway from this entire article. As an expert in this field, my advice is unequivocal: Do not do it. The "L" in A2L stands for low burning velocity, which means it’s less likely to explode than propane, but it is still classified as flammable. All it needs is the right fuel-air mixture and an ignition source. Your halogen leak detector provides that ignition source by design.

It is a fundamental principle of workplace safety to never bring a potential spark into an environment with a potential fuel source. Using a non-A2L-rated tool to hunt for a flammable gas leak violates this principle. Any potential cost savings from using an old tool are instantly erased by the immense risk of fire, property damage, and personal injury.

What makes a leak detector "A2L compatible"?

If your old detector is unsafe, what should you be using? The market is full of options, but you need to know which technologies are both effective and safe for modern refrigerants.

An A2L-compatible detector is one that is certified as intrinsically safe, meaning its design prevents it from creating a spark. The most common and effective safe technologies are Infrared (IR) and modern Heated Diode sensors.

Choosing a new leak detector means choosing a new technology. Here’s a breakdown of how the modern, safe options compare to the old standard.

For a professional who wants the best tool, an Infrared (IR) detector is the top choice. It doesn’t get triggered by other chemicals, and the sensor practically lasts forever. A Heated Diode detector is also an excellent and safe choice, offering great sensitivity for a lower price point.

What is installed to detect leaks at the indoor unit?

You’ve heard that some new systems have their own leak detectors built-in. You wonder what these are and how they are different from your handheld tool.

For A2L systems, building codes often require a permanently installed refrigerant sensor near the indoor coil. This is a stationary safety device, not a troubleshooting tool, designed to automatically mitigate a leak by shutting down the system and activating an alarm.

This is a key difference between a tool and a safety system. Your handheld detector is what you use to find a leak. The installed sensor is what the building uses to protect its occupants.

• Function: It constantly monitors the air around the indoor unit.
• Location: It’s placed in a strategic spot where leaking refrigerant, which is heavier than air, would accumulate.
• Action: If it detects a refrigerant concentration that exceeds a preset safety limit, it sends a signal to the HVAC system’s main control board. The system will then immediately shut down to stop the leak from worsening and will often activate an audible alarm and sometimes even a ventilation fan to disperse the refrigerant. This is an engineered safety control required for the safe application of these new refrigerants.

Final Thoughts

The shift to A2L refrigerants requires a shift in our tools and our mindset. Retiring your old halogen detector isn’t just about compliance or accuracy; it’s a critical step in ensuring your safety on every single job.