Refrigerant Leaks in the A2L Era: What Changed in 2025 and 2026, and How Leaks Show Themselves

• Most new comfort cooling equipment, including chillers, has been limited to refrigerants under 700 GWP since January 1, 2025. That means A2L refrigerants such as R-32 and R-454B.
• From January 1, 2026, HFC appliances with 15 pounds (6.8 kg) or more must repair leaks above set annual rates. The rates are 10% for comfort cooling, 20% for commercial refrigeration and 30% for industrial process.
• Without a detector, refrigerant leaks often show as oily, dust attracting stains, because refrigerant carries compressor oil out with it.
• A generic volatile organic compound (VOC) sensor does not reliably detect most refrigerants. Refrigerant monitors must be matched to the refrigerant family, and A2L systems use detectors listed for that purpose.

Refrigerant leaks because a refrigeration circuit is a sealed system under pressure with many joints, valves and thin walled tubes, and every one can open over time. Vibration, temperature swings and corrosion do the opening.

The circuit runs at high pressure on the condenser side and lower pressure on the evaporator side, around the clock. Small defects that would never leak water can pass refrigerant gas.

Vibration is the most common driver. Compressors and fans shake the tubing, and where a tube touches a frame or another tube, it slowly wears through.

Joints are the next. Flare and brazed joints, like the water joints in Part 2, age with every heat and cool cycle.

Refrigerant leaks happen most at joints, valves and points of rubbing. The common leak points are well known.

• Flare and brazed joints throughout the circuit.
• Schrader valve cores, the small service valves used to connect service hoses.
• Service valves and their caps and packing.
• Sight glass and filter drier connections.
• Vibration rubbed tubing where lines touch frames or each other.
• Coil return bends, the U shaped ends of evaporator and condenser coils.

A missing cap on a Schrader valve is a small finding with a big effect. The cap is a secondary seal, and a core without one can leak slowly for months.

You can often see a refrigerant leak without a detector, because refrigerant carries compressor oil. A leak leaves an oily, dust attracting stain at the leak point. The stain marks where the gas has been escaping.

• Oily stains at joints, valves and coil connections.
• Frost or ice in unusual places, where expanding refrigerant chills the metal.
• Bubbles in a liquid line sight glass, showing gas where there should be liquid.
• A falling oil level in the compressor sight glass.

Routine visual inspection finds most of these, because the marks are visible from a walkway. Frost in odd places can also show up in thermal imaging as an unexpected cold spot.

A pressurized gas leak makes high frequency turbulence. Airborne ultrasound can locate it even when the leak is too small to see or hear, which is useful in a loud plant room.

On January 1, 2025, a 700 GWP limit took effect for most new comfort cooling equipment, including chillers. It comes from the EPA Technology Transitions rule under the American Innovation and Manufacturing (AIM) Act. New equipment had to move off high GWP refrigerants.

R-410A, the long standing comfort cooling refrigerant, has a GWP of 2,088. Common replacements are R-32, with a GWP of about 675, and R-454B, at about 466 (Greenheck).

The rule applies to new equipment. Existing R-410A systems can keep running and be serviced.

Will the rule be reversed?

The EPA said in 2025 it would reconsider parts of the rule. Manufacturers have already moved comfort cooling to A2L refrigerants, and a return to R-410A is considered unlikely (ACHR News).

In practice, a building replacing a chiller or rooftop unit today is almost certainly installing an A2L refrigerant. That changes how leaks should be detected and managed in that room, and which monitors it needs.

An A2L refrigerant is one classed as lower toxicity and lower flammability, meaning mildly flammable. R-32 and R-454B are A2L refrigerants.

The classification comes from ASHRAE Standard 34, which classes refrigerants by toxicity and flammability. The letter is toxicity, with A the lower class; the number and letter after it are flammability.

Mildly flammable means an A2L refrigerant can burn under the right conditions, though it is far harder to ignite than a fully flammable gas. That is why A2L equipment comes with added safety rules.

ASHRAE Standard 15 and UL 60335-2-40 set safety requirements for A2L equipment, such as charge limits, ventilation and refrigerant detection. UL is the safety standards organization behind the equipment standard.

The EPA's Emissions Reduction and Reclamation (ER&R) rule requires owners of larger HFC appliances to repair leaks above set annual leak rates from January 1, 2026. The rule was published on October 11, 2024 (EPA fact sheet).

It applies to appliances with a full charge of 15 pounds (6.8 kg) or more of an HFC, or a substitute, with a GWP above 53. Leak rates are measured as a percentage of full charge per year.

• Comfort cooling and other appliances: repair leaks above 10%.
• Commercial refrigeration: repair leaks above 20%.
• Industrial process refrigeration: repair leaks above 30%.

Automatic leak detection and reporting

Automatic leak detection (ALD) is required for commercial refrigeration and industrial process refrigeration systems with 1,500 pounds (680 kg) or more of charge (HVAC Insider).

Owners of appliances with 15 pounds (6.8 kg) or more that leak 125% or more of full charge in a calendar year must report to EPA. That is a system that has lost more than its entire charge in a year.

The practical effect is that every top up now matters. Refrigerant added to a system is the evidence used to calculate its leak rate.

You track a system's leak rate by recording every addition of refrigerant against the system's full charge. The service log becomes the leak record.

1. 1. List every system with 15 pounds (6.8 kg) or more of HFC, with its refrigerant type and full charge.
2. 2. Record every refrigerant addition: date, amount, technician and the reason given.
3. 3. Compare the additions with the full charge to see the annual leak rate for each system.
4. 4. Flag any system approaching its threshold: 10% for comfort cooling, 20% for commercial refrigeration, 30% for industrial process refrigeration.
5. 5. Keep repair and verification records with the service log.

This is a recordkeeping task as much as a technical one. A system that is topped up quietly every few months, with no leak search, is exactly what the rule is designed to stop. Rules and deadlines should be confirmed against the EPA fact sheet and a qualified technician.

A generic gas or VOC sensor cannot find every refrigerant leak because most refrigerants are not detected reliably by VOC sensing. The sensor technology has to match the gas.

Refrigerant monitors use sensor technology matched to the refrigerant family. A monitor set up for one refrigerant may respond weakly, or not at all, to another.

A2L systems use detectors listed for that purpose. Where an A2L refrigerant is installed, the detection that comes with or is required for that equipment matters more than any general purpose air sensor.

That makes the match worth checking. Rooms that now hold a mix of old R-410A or R-134a equipment and new A2L equipment may have monitors chosen for the old refrigerant only.

Refrigerant leaks are a safety issue because most refrigerants are heavier than air and collect at low points. In an enclosed machinery room, a large leak can displace oxygen.

That is why machinery rooms use refrigerant monitors and alarms tied to ventilation. The alarm starts exhaust fans and warns people before levels become dangerous.

A2L refrigerants add mild flammability to that picture. Charge limits, ventilation and detection exist to keep concentrations well below the point where ignition is possible.

A refrigerant alarm should be treated as real until proven otherwise. Site procedures for evacuation, ventilation and re-entry come first, and investigation comes after.

When a refrigerant monitor alarms, people come first: follow the site's alarm procedure, let the ventilation run and keep people out until levels are confirmed safe. The leak search comes after.

1. 1. Treat the alarm as real and follow the site's evacuation and notification procedure.
2. 2. Confirm the machinery room exhaust has started, as the alarm is designed to trigger it.
3. 3. Do not re-enter until the monitor reading has fallen and the procedure allows entry.
4. 4. Record the alarm time, reading and which equipment was running.
5. 5. Have a certified technician find and repair the leak, and record the refrigerant added.

Alarm history is worth reading on every round. A monitor that has alarmed and cleared several times may be catching an intermittent leak, or reacting to cleaning chemicals, and both need an answer.

Technicians find the exact leak point with an electronic leak detector, a bubble test or a pressure test. Each narrows the search in a different way.

• Electronic leak detector: a handheld probe moved slowly along joints and valves to sense escaping refrigerant.
• Bubble test: a soap solution brushed on a suspect joint, which bubbles where gas escapes.
• Pressure test: the circuit pressurized and watched for pressure loss, used when the leak cannot be found on a running system.

A walk past makes the technician's job faster. An oily stain, a frosted fitting or an ultrasonic hiss tells them where to start, instead of searching the whole circuit.

A slow leak lowers capacity and efficiency long before a low pressure trip. The chiller keeps running, just worse.

Rising approach temperatures and falling suction pressure are typical trends. Both show on the chiller panel, covered in Rotating Equipment Part 7.

An undercharged system also runs its compressor harder for the same cooling. That raises energy use and wear, and in screw and scroll compressors it can affect oil return.

Comparing panel readings round by round is how a slow leak shows up as a trend. A chiller whose suction pressure creeps down over weeks is telling you it is losing charge.

A refrigerant leak costs cooling, energy and compliance effort, and replacement refrigerant is expensive.

In an office building

Lost cooling capacity, higher energy use, recordkeeping and repair deadlines under the 2026 rule, and refrigerant replacement cost are the main burdens. Refrigerant checks belong in routine heating, ventilation and air conditioning (HVAC) work, covered in HVAC maintenance in office buildings. Those routines rarely include a review of the refrigerant service log, which is now where compliance lives.

In a data center

Lost chiller or computer room air conditioner (CRAC) capacity cuts into critical cooling. Safety alarms can force a room evacuation at the worst possible time.

Direct liquid cooling does not remove refrigerant from the site. The chillers behind the facility water system still hold it, as covered in Part 5.

Several things mimic the signs of a refrigerant leak. Knowing them prevents both false alarms and missed leaks.

• Oil stains from a compressor or gearbox oil leak that is not refrigerant, covered in Part 4.
• Frost from low airflow or a low load condition rather than a leak, covered in the Moisture and Air sub-series.
• Nuisance alarms from refrigerant monitors exposed to cleaning chemicals or solvents.

An oil stain at a refrigerant joint is a leak sign; an oil stain under a compressor crankcase may be an oil leak. A monitor that alarms every time the floor is cleaned is reacting to the cleaner.

This is why no single sensor is enough. Stains, frost, sight glass, panel trends and a matched monitor each rule out a different explanation.

A walk past can prove that a system shows leak signs and that a monitor has alarmed. It cannot prove the exact leak point or the leak rate.

• Directly observable: oily stains at joints, frost in unusual places, bubbles in a sight glass, and refrigerant monitor alarms on display.
• Strong indicator: falling suction pressure and rising approach temperatures on the chiller panel, and repeated top ups in the service log.
• Suspected: the exact leak point and leak rate. Those need an electronic leak detector, bubble test or pressure test by a certified technician.

That is the limit of any route based check. It finds the system that is leaking; a certified technician finds and repairs the leak.

A walkthrough record that captures sight glasses, monitor displays and panel readings each round turns these checks into a trend, the core of predictive maintenance.

• Oily stains at joints, valves and coil connections.
• Liquid line sight glasses for bubbles.
• The refrigerant monitor display and alarm history.
• Frost in places it does not usually form.
• Refrigerant lines not rubbing on frames or each other.
• Chiller suction pressure and approaches compared with the last round.

Coming Soon

1. 1. Which of your systems hold 15 pounds or more of HFC refrigerant?
2. 2. How much refrigerant was added to each system in the last 12 months?
3. 3. Are your refrigerant monitors matched to the refrigerants actually in the room?
4. 4. When were refrigerant monitors last calibrated?
5. 5. Which new or replaced equipment on site uses an A2L refrigerant?

What are the EPA refrigerant leak repair rules for 2026?

From January 1, 2026, the EPA's Emissions Reduction and Reclamation rule applies to HFC appliances with 15 pounds or more. Leaks above set annual rates must be repaired. The thresholds are 10% for comfort cooling, 20% for commercial refrigeration and 30% for industrial process refrigeration.

What does A2L refrigerant mean?

A2L is an ASHRAE Standard 34 safety class meaning lower toxicity and lower flammability, or mildly flammable. R-32 and R-454B are A2L refrigerants used in new comfort cooling equipment.

Is R-410A banned?

Not for existing systems. Since January 1, 2025, most new comfort cooling equipment must use refrigerants under 700 GWP, which rules out R-410A in new units. Existing R-410A systems can keep running and be serviced.

What is the GWP of R-32 and R-454B?

R-32 has a GWP of about 675 and R-454B about 466. For comparison, R-410A has a GWP of 2,088.

How can you tell if a chiller is leaking refrigerant?

Look for oily stains at joints and valves, frost in unusual places and bubbles in the liquid line sight glass. On the panel, falling suction pressure and rising approach temperatures are typical, and repeated top ups in the service log confirm a leak.

What leak rate triggers repair for comfort cooling?

For comfort cooling appliances covered by the 2026 rule, leaks above 10% of full charge per year must be repaired. Commercial refrigeration is 20% and industrial process refrigeration 30%.

Can a VOC sensor detect refrigerant leaks?

Not reliably for most refrigerants. Refrigerant monitors use sensor technology matched to the refrigerant family, and A2L systems use detectors listed for that purpose.

Are refrigerant leaks dangerous?

They can be. Most refrigerants are heavier than air and collect at low points, and in an enclosed machinery room a large leak can displace oxygen. A2L refrigerants are also mildly flammable, which is why charge limits, ventilation and detection apply.

Do I need automatic leak detection?

Under the EPA rule, automatic leak detection is required for commercial refrigeration and industrial process refrigeration systems with 1,500 pounds or more of charge. A2L equipment may also need refrigerant detection under its own safety standards.

• HVAC Maintenance for Office Buildings: What ASHRAE 180 Expects and What Owners Miss
• VOC and Gas Sensing for Data Centers, and the Sensor Family That Smells Trouble First
• Chiller Compressor Distress: Surge, Lift and the Panel Readings That Warn Before a Trip

• EPA: ER&R leak repair fact sheet (January 2026)
• HVAC Insider: ER&R thresholds and automatic leak detection
• ACHR News: Technology Transitions 700 GWP limit and reconsideration
• Greenheck: A2L classification and GWP values