Automatic Leak Detection Requirements Under 40 CFR § 84.108

Section 84.108 of the EPA's Emissions Reduction and Reclamation rule establishes when automatic leak detection (ALD) systems are required, what technology they must use, and what happens when they detect a leak. This guide covers who is affected, the installation deadlines, the two approved detection approaches, and how ALD interacts with the broader leak repair requirements of Subpart C.

What Is an Automatic Leak Detection System?

An automatic leak detection system continuously monitors for refrigerant leaks without requiring a technician to physically inspect the equipment. These systems use sensors to detect either the presence of refrigerant vapor in the surrounding air or changes in appliance operating conditions that indicate refrigerant loss. When a threshold is reached, the system generates an alert so the owner can investigate and respond.

ALD requirements are codified in 40 CFR § 84.108, which is separate from the leak repair provisions in § 84.106 but works in conjunction with them. Understanding both sections is necessary to grasp the full compliance picture.

Who Must Install ALD?

ALD is not required for all refrigerant-containing equipment. Under § 84.108(a), ALD applies only to appliances that meet all three of the following criteria:

Equipment type: The appliance is used for industrial process refrigeration or commercial refrigeration
Charge size: The appliance has a full charge of 1,500 pounds or greater
Refrigerant type: The appliance contains a regulated substance or a substitute with a GWP greater than 53

Key Exemptions

Category	ALD Required?	Reason
Comfort cooling (AC, heat pumps)	No	Exempt regardless of charge size
Commercial/industrial refrigeration under 1,500 lbs	No	Below the charge size threshold
Equipment installed before January 1, 2017	No	Grandfathered under the regulation
Equipment using refrigerants with GWP ≤ 53	No	Below the GWP threshold (e.g., CO₂, propane, ammonia)

In practice, the ALD requirement targets large supermarket refrigeration systems, cold storage warehouses, food processing facilities, and industrial refrigeration plants. A typical grocery store rack system using R-404A with a 2,000-pound charge would be subject to ALD. An office building chiller using R-410A, regardless of size, would not — it falls under comfort cooling.

Installation Deadlines

Under § 84.108(b), the installation deadline depends on when the appliance was first put into service:

Appliance Installation Date	ALD Installation Deadline
On or after January 1, 2026	Upon installation or within 30 days
Between January 1, 2017 and January 1, 2026	By January 1, 2027
Before January 1, 2017	Not required

The January 1, 2027 deadline for existing equipment (installed 2017–2025) gives owners approximately one year from the regulation's effective date to procure and install ALD systems. Equipment installed before 2017 is fully exempt, though owners may still choose to install ALD voluntarily to take advantage of the inspection reduction benefit described below.

Technical Requirements: Two Approved Approaches

Section 84.108 defines two categories of ALD systems that satisfy the regulation. An owner may use either approach, or a combination, as long as the applicable requirements are met.

Approach 1: Direct Refrigerant Detection in Air (§ 84.108(f))

This approach places sensors in the area surrounding the equipment to detect refrigerant vapor in the ambient air. The regulation specifies:

Sensors or sensor intakes must be positioned for continuous monitoring of refrigerant concentrations near the compressor, evaporator, condenser, and other areas with high leak potential
The system must be capable of accurately detecting 10 parts per million (ppm) of vapor of the specific refrigerant in use
The system must alert the owner or operator when the concentration reaches 100 ppm

The 10 ppm detection floor and 100 ppm alarm threshold are significant specifications that eliminate lower-sensitivity sensor technologies from consideration. This effectively requires non-dispersive infrared (NDIR) sensors, which are the only commercially available technology that reliably meets the 10 ppm detection requirement for common HFC refrigerants.

Approach 2: Appliance Condition Monitoring (§ 84.108(g))

Instead of detecting refrigerant vapor in the air, this approach monitors the appliance's operating parameters to identify conditions that indicate refrigerant loss. The regulation specifies:

The system must automatically alert when measurements indicate a loss of 50 pounds of refrigerant or 10% of the full charge, whichever is less

Condition monitoring systems typically track metrics like suction pressure, discharge pressure, superheat, subcooling, and compressor runtime to infer refrigerant charge status. For a 1,500-pound system, the 10% threshold (150 lbs) would apply since it is less than 50 lbs only on systems below 500 lbs — which would not meet the ALD applicability threshold anyway. In practice, for systems at or above 1,500 lbs, the trigger is always 50 pounds.

General Requirements for Both Approaches

The system must be installed per the manufacturer's instructions (§ 84.108(c))
The system must be audited and calibrated annually (§ 84.108(d))
ALD is only required for components located inside an enclosed building or structure — outdoor components are not required to be monitored (§ 84.108(e))

ALD Sensor Technologies

For owners evaluating direct refrigerant detection systems (Approach 1), understanding the available sensor technologies is important because not all of them meet the regulation's 10 ppm detection requirement.

Technology	Detection Limit	Calibration	Typical Lifespan	Meets § 84.108(f)?
NDIR (Non-Dispersive Infrared)	~1–10 ppm	Self-stable; minimal drift	10+ years	Yes
MOS (Metal Oxide Semiconductor)	~100 ppm	Every 6 months	2–4 years	No
Thermal Conductivity	Variable	Periodic	Variable	Depends on model

NDIR sensors are the industry standard for § 84.108(f) compliance. They detect refrigerant by measuring infrared light absorption at wavelengths specific to the target gas. Their long-term stability and low maintenance requirements make them well-suited to continuous monitoring applications. MOS (semiconductor) sensors, while inexpensive, cannot meet the 10 ppm detection threshold and are generally unsuitable for regulatory compliance.

Major manufacturers of ALD systems designed for commercial refrigeration compliance include MSA Bacharach (MGS series), Danfoss (DGS gas sensor series), and Copeland/Emerson (Refrigerant Leak Detection System in 4-zone and 16-zone configurations). When selecting a system, verify that the manufacturer explicitly certifies compliance with § 84.108(f) detection and alarm thresholds for your specific refrigerant type.

What Happens When ALD Detects a Leak?

When the ALD system triggers an alert, the owner or operator has two response options under § 84.108(h):

Option 1: Calculate the Leak Rate First

Under § 84.108(h)(1), the owner must calculate the leak rate within 30 days of the ALD alert (or 120 days if an industrial process shutdown is required to access the equipment). If the calculated leak rate exceeds the applicable threshold under § 84.106(c)(2), the owner must then comply with the full leak repair requirements — including the 30-day repair deadline, verification testing, and potential retrofit/retirement obligations.

Option 2: Repair First, Then Calculate

Under § 84.108(h)(2), the owner may choose to proactively repair the identified leak(s) before adding refrigerant to the appliance, then calculate the leak rate afterward. If the rate still exceeds the threshold after repair, the full § 84.106 compliance path applies.

Important caveat: Where ALD monitors only a portion of the appliance (for example, indoor components only), the unmonitored sections remain subject to the applicable periodic leak inspection requirements under § 84.106(g). ALD does not create a blanket exemption — it only covers what it actually monitors.

How ALD Reduces Manual Inspection Requirements

One of the most significant compliance benefits of ALD is that it can replace periodic manual leak inspections. Under § 84.106(g)(4), quarterly or annual leak inspections are not required on appliances (or portions of appliances) that are continuously monitored by an ALD system that is audited or calibrated annually.

Without ALD, the inspection schedule after a leak rate exceedance is:

Appliances with 500+ pounds: quarterly leak inspections
Appliances with 15–500 pounds: annual leak inspections

These inspections must continue until four consecutive quarters (or one year) show no exceedance. For large facilities with dozens of units, replacing quarterly manual inspections with continuous ALD monitoring can represent substantial operational savings — and provides earlier leak detection, which reduces refrigerant loss and the likelihood of triggering repair or retrofit/retirement obligations.

Related ASHRAE Standards

In addition to the EPA regulation, two ASHRAE standards are relevant to leak detection system design and installation:

ASHRAE Standard 15 — Safety Standard for Refrigeration Systems

Requires refrigerant detectors in each machinery room, positioned where leaked refrigerant will concentrate. Detectors must actuate both an alarm and mechanical ventilation at a setpoint not exceeding the Occupational Exposure Limit (OEL) per ASHRAE Standard 34. Alarms must be visual and audible, located both inside the room and outside each entrance, and must require manual reset. For A2L refrigerants, systems over 4 pounds must have factory-installed detectors that alarm within 30 seconds and begin mitigation within 15 seconds.

ASHRAE Standard 147 — Reducing the Release of Halogenated Refrigerants

Establishes practices and procedures to reduce inadvertent release of halogenated refrigerants across all lifecycle stages: manufacture, installation, testing, operation, maintenance, repair, and disposal. This standard complements the ALD requirement by addressing the broader operational context in which leak detection fits.

Note that ASHRAE Standard 15 has its own leak detection requirements that may apply independently of § 84.108, particularly for machinery rooms and systems using A2L (mildly flammable) refrigerants. Owners should ensure their ALD installations satisfy both sets of requirements where applicable.

Recordkeeping Requirements

Under § 84.108(i), owners must maintain records for three years covering:

System installation date and details
Annual audit and calibration dates and results
Dates the system identified a leak
Locations of leaks that triggered alarms

These records must be available for EPA inspection upon request. For owners using ALD to replace manual inspections, maintaining thorough ALD records is especially important — if the records do not demonstrate continuous monitoring and annual calibration, the inspection reduction benefit under § 84.106(g)(4) does not apply, and the owner may be found non-compliant with the manual inspection schedule they were supposed to be following. See our recordkeeping requirements guide for the broader context of what records must be maintained under Subpart C.

Penalties for Non-Compliance

Failure to install or maintain a required ALD system is enforceable under the AIM Act's civil penalty authority. Under 42 U.S.C. § 7675(k), violations of Subpart C carry penalties of up to $69,733 per violation per day (as adjusted for inflation). Each day of operation without a required ALD system can constitute a separate violation.

Beyond the direct ALD violation, operating without leak detection may lead to undetected leaks that trigger additional violations under § 84.106 — including failure to calculate leak rates, failure to repair within required timelines, and failure to maintain records. For a detailed look at how the EPA has enforced refrigerant violations, see our enforcement cases article.

Frequently Asked Questions

Does my office building chiller need ALD?

No. Comfort cooling equipment — including chillers used for air conditioning — is exempt from ALD requirements under § 84.108 regardless of charge size. ALD applies only to commercial and industrial process refrigeration.

My supermarket system was installed in 2015. Do I need ALD?

No. Equipment installed before January 1, 2017 is grandfathered and not subject to the ALD installation requirement. However, you may still benefit from voluntary ALD installation to reduce manual inspection obligations and catch leaks earlier.

Do I need to monitor outdoor condensers?

No. Section 84.108(e) requires ALD only for components located inside an enclosed building or structure. Outdoor components are excluded. However, if your ALD only covers indoor components, the outdoor portions remain subject to manual leak inspection requirements under § 84.106(g).

Can ALD completely replace all manual leak inspections?

Only for the portions of the appliance that the ALD system actually monitors. If outdoor components or other sections are not covered by ALD, those areas still require periodic manual inspection per § 84.106(g). Full replacement of manual inspections is possible only if ALD covers the entire appliance.

What if my ALD system goes offline or loses calibration?

The regulation requires annual auditing and calibration. If your system is not operational or calibrated, you lose the inspection reduction benefit and must resume the applicable manual inspection schedule. Maintaining continuous operation and documenting annual calibration is essential to preserving the compliance advantage.

Related Resources

EPA Subpart C: Complete Compliance Checklist for 2026 — Overview of all Subpart C requirements including leak repair
Recordkeeping Requirements Under § 84.106 — Full guide to documentation obligations including ALD records
Free EPA Leak Rate Calculator — Calculate whether your equipment exceeds the applicable threshold
Retrofit vs. Retirement: Making the Decision Under Subpart C — What happens when leak repair is not enough
Who Gets Fined? Real EPA Enforcement Cases — Documented penalties for refrigerant violations