Automatic Leak Detection Requirements Under the AIM Act: Which Systems Need ALD and By When
The AIM Act introduced a requirement that has no precedent under Section 608: mandatory automatic leak detection (ALD) systems for large commercial and industrial refrigeration equipment. If you service or manage systems with charges of 1,500 pounds or more, this requirement is already in effect for new installations and carries a January 2027 deadline for existing systems.
This guide covers exactly which systems are affected, the three-tier compliance timeline, the technical specifications ALD systems must meet, calibration and documentation requirements, and the practical considerations for contractors responsible for installing and maintaining these systems.
Which systems require ALD?
The ALD requirement under 40 CFR Part 84, Section 84.108 applies to commercial and industrial process refrigeration systems containing 1,500 pounds or more of a regulated substance (HFC refrigerant with GWP above 53).
In practical terms, this covers large supermarket rack systems (which commonly hold 2,000–5,000+ pounds), cold storage and distribution center refrigeration, food processing facility systems, industrial process cooling used in manufacturing, and pharmaceutical cold chain systems.
Systems that do NOT require ALD, regardless of charge size: comfort cooling systems (commercial AC, chillers, rooftop units, VRF systems). The ALD mandate is specific to commercial refrigeration and industrial process refrigeration. A 2,000-pound chiller used for building comfort cooling is not subject to ALD requirements — though it remains subject to all other Subpart C leak repair and documentation requirements.
Systems below 1,500 pounds are also exempt from ALD, even if they are commercial or industrial refrigeration. A 200-pound walk-in freezer must comply with Subpart C leak rate calculations and repair timelines but does not need automatic leak detection.
The three-tier compliance timeline
The EPA established staggered deadlines based on when the system was installed, giving operators time to plan and budget for ALD retrofits.
Tier 1 — New systems installed after January 1, 2026: ALD must be installed within 30 days of the system being commissioned. This is already in effect. Any new commercial or industrial refrigeration system with a charge of 1,500+ pounds that was commissioned on or after January 1, 2026 should already have ALD operational or in the installation pipeline.
Tier 2 — Existing systems installed between January 1, 2017 and December 31, 2025: ALD must be installed by January 1, 2027. This is the deadline that will affect the largest number of systems. Operators and contractors have approximately 11 months remaining to identify qualifying systems, select ALD solutions, and complete installations.
Tier 3 — Systems installed before January 1, 2017: These systems are exempt from ALD requirements. However, they remain fully subject to all other Subpart C obligations including leak rate calculations, repair timelines, chronic leaker reporting, and documentation requirements. The ALD exemption does not mean these systems operate outside of federal oversight.
The installation date that determines which tier applies is the date the system was initially commissioned — not the date of any subsequent modification, repair, or refrigerant change.
Direct vs. indirect detection methods
The regulations permit two approaches to automatic leak detection, each with specific technical requirements.
Direct detection (sensor-based)
Direct detection uses refrigerant sensors placed in areas where leaks are most likely to occur. Under Section 84.108, direct detection systems must meet these specifications.
Detection threshold: Sensors must be capable of detecting refrigerant concentrations as low as 10 parts per million (ppm). This is a very sensitive threshold — most commercial refrigerant sensors meet this requirement, but it should be verified in product specifications.
Alert threshold: The system must trigger an alert at 100 ppm. This alert must be communicated to the system operator in a timely manner — typically through a building automation system, alarm panel, or remote notification.
Sensor placement is critical and must cover areas most likely to experience leaks. The regulations specify areas near compressors, evaporators, condensers, receivers, and connection points. Outdoor components of a system may not be practically monitored by indoor sensors — for outdoor components, the regulations allow periodic manual inspections in lieu of continuous sensor monitoring.
Monitoring frequency: Direct detection systems must provide continuous or near-continuous monitoring. The intent is real-time leak identification, not periodic sampling.
Indirect detection (monitoring-based)
Indirect detection infers refrigerant loss through system performance monitoring rather than direct sensing of refrigerant in the air. Under Section 84.108, indirect detection systems must meet these specifications.
Detection capability: The system must be capable of identifying a refrigerant loss of 50 pounds or 10% of the full charge, whichever is less. For a 2,000-pound system, this means the system must detect a loss as small as 50 pounds (since 10% of 2,000 = 200 pounds, and 50 is less than 200). For a 4,000-pound system, the threshold remains 50 pounds (since 50 is less than 400).
Methods include: refrigerant pressure monitoring with temperature compensation, refrigerant level monitoring in receivers, charge calculation based on system performance parameters, or mass flow monitoring at key system points.
Monitoring frequency: Indirect systems must also provide continuous or near-continuous monitoring with automated alerting when the detection threshold is reached.
Which method should you recommend to customers?
Direct detection (sensors) is more common in commercial installations because the technology is mature, installation is relatively straightforward, and sensors provide unambiguous evidence of refrigerant in the air. Indirect detection is more commonly used in industrial process applications where sensor placement may be impractical or where system complexity makes performance monitoring more informative.
Many large installations use both methods in combination — sensors in the machine room and enclosed spaces, plus system performance monitoring for outdoor and distributed components. This hybrid approach provides the most comprehensive coverage.
Calibration requirements
ALD systems are only useful if they work accurately. The AIM Act mandates annual calibration with specific documentation.
Frequency: All ALD systems must be calibrated at least once per year, regardless of whether the system uses direct or indirect detection.
Documentation for each calibration must include:
- The date of calibration
- The calibration method or standard used
- The identity of the person or company performing the calibration
- Confirmation that all sensors/monitors met the required detection thresholds post-calibration
- Any sensors or components that were replaced during calibration
Calibration records must be maintained for at least 3 years and be available for EPA inspection upon request.
Overdue calibrations are violations. If a system’s ALD calibration lapses, the system is technically non-compliant even if no leak has occurred. This makes calibration scheduling and tracking essential — a missed annual calibration due to a scheduling oversight creates unnecessary violation exposure.
Practical considerations for contractors
If you service large commercial or industrial refrigeration systems, the ALD requirements create both obligations and business opportunities.
You may be responsible for advising customers. Building owners and facility managers may not be aware of the ALD requirements for their existing systems. If you service systems that were installed between 2017 and 2025 with charges of 1,500+ pounds, proactively informing customers of the January 2027 deadline — and providing installation quotes — is both a compliance service and a revenue opportunity.
Document ALD status in your equipment records. For every system you service, your records should indicate whether ALD is installed, the installation date, the last calibration date, and the next calibration due date. When you log a service event on a system with ALD, note whether the service was triggered by an ALD alert or identified through other means. This “triggered by ALD” documentation can be relevant if EPA questions the timeliness of your leak response.
Coordinate with ALD system vendors. ALD installation and calibration may be performed by the HVAC contractor, the ALD system manufacturer, or a specialized controls contractor. Regardless of who performs the work, the compliance responsibility rests with the system owner — and the documentation must be complete and accessible.
Budget for annual calibrations. For customers with multiple large systems, annual ALD calibrations represent recurring service revenue. Include calibration scheduling in your service agreements and build it into your compliance tracking so that due dates are not missed.
ALD tracking at scale
For contractors managing 10 or more systems with ALD requirements across multiple customer locations, tracking calibration dates, installation deadlines, and alert documentation manually becomes a coordination challenge. A missed calibration date on a single system at a single location creates a violation — and when you are tracking calibrations across 30 systems at 15 locations, the probability of a scheduling gap increases with every system added.
RefriComply’s Pro and Business tiers include dedicated ALD tracking. The system records ALD installation dates, auto-calculates calibration due dates, sends alerts when calibrations approach, and logs whether service events were triggered by ALD alerts. When an EPA inspector asks about ALD compliance for a specific system, you generate the complete history in seconds.
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