Quick background (why leak rate matters)

EPA uses leak rate to decide when owners/operators must repair, retrofit, or retire refrigerant‑containing equipment.

• For ozone‑depleting substances (ODS) (e.g., CFC/HCFC) in appliances with ≥ 50 lb full charge, leak‑repair is governed by 40 CFR Part 82 Subpart F. Trigger rates: 30% (industrial process refrigeration), 20% (commercial refrigeration), 10% (comfort cooling/other); typical repair timelines are 30 days (or 120 days if an industrial process shutdown is needed). (eCFR)
• For HFCs and certain substitutes (GWP > 53) in appliances with ≥ 15 lb full charge, leak‑repair is required under the AIM Act regulations at 40 CFR Part 84 Subpart C effective January 1, 2026; trigger rates are the same 10/20/30% by category. (eCFR)

EPA’s definition of “leak rate” (and “full charge”)

EPA defines leak rate as the percent of an appliance’s full charge that would be lost over 12 months if the current loss rate continued. EPA authorizes two calculation methods, and you must use one method consistently across appliances at a facility (with limited exceptions noted below). Full charge is the amount of refrigerant at normal operating conditions, determined by manufacturer data, engineering calculation, measured charge, or a documented range (midpoint). See 40 CFR § 82.152 (Definitions) for ODS and parallel language in 40 CFR § 84.102/§ 84.106 for HFCs. (eCFR)

The two official formulas

1) Annualizing Method

Use when you’ve just added refrigerant; annualize that addition over the days since the last addition.

Leak Rate (%) = (lbs_added / full_charge_lbs) * (365 / MIN(days_since_last_addition, 365)) * 100

This is the four‑step “annualizing” calculation in § 82.152 (same concept for HFCs).

Copy‑paste (Excel/Sheets): =(lbs_added / full_charge_lbs) * (365 / MIN(days_since_last_addition, 365)) * 100

2) Rolling Average Method

Use the sum of all refrigerant added in the last 365 days (or since the last successful follow‑up verification test if that was < 1 year ago).

EPA defines both methods and requires one method per facility; switching methods is only allowed in specific change‑of‑ownership scenarios (see § 84.106(b)(3) for HFCs).

First calculation under the HFC rule (2026 start): For annualizing, use 365 days for the first post‑Jan 1, 2026 calculation; for rolling, use lbs added since Jan 1, 2026 (then a true 365‑day window thereafter). § 84.106(b)(1)–(2).

When you must calculate the leak rate

Every time you add refrigerant, unless the addition is immediately after a new install/retrofit or qualifies as a “seasonal variance.” See § 82.157(b) (ODS) and § 84.106(b) (HFCs).

Repair triggers (what counts as “too high”?)

Compare your calculated leak rate to the applicable trigger for the appliance category:

• Comfort cooling/other (and refrigerated transport under Part 84): 10%
• Commercial refrigeration: 20%
• Industrial process refrigeration (IPR): 30%

Triggers and timelines appear in § 82.157(c)–(f) (ODS, ≥ 50 lb) and § 84.106(c)–(f) (HFCs, ≥ 15 lb), including 30‑day repair (or 120‑day if a process shutdown is required), verification testing, and allowed extensions.

Worked examples

Assume each appliance has a documented full charge per EPA definitions.

A) Annualizing Method (comfort cooling)

• Full charge: 120 lb
• Added: 6 lb
• Days since last addition: 90
• Leak rate = (6/120) × (365/90) × 100 = 20.28%

Result: 20.3% exceeds the 10% comfort‑cooling trigger → repair required.

B) Rolling Average (commercial refrigeration)

• Full charge: 500 lb
• Added last 365 days: 60 lb → 12.0% (no trigger)
• If the total were 120 lb, leak rate 24.0% → repair required (> 20%).

C) Annualizing vs Rolling (why results can differ)

• Full charge: 100 lb; 4 lb added after 30 days
• Annualizing = (4/100) × (365/30) × 100 = 48.67% → triggers in any category
• Rolling = 4/100 × 100 = 4% → no trigger yet

Pick a method and use it consistently across the facility.

D) “Chronically leaking” reporting (≥ 125% in a calendar year)

• Full charge: 300 lb; total added during the calendar year: 380 lb
• Annual percent loss: 380/300 × 100 = 126.7%

Result: You must file a chronically leaking‑appliance report to EPA by March 1 of the following year. This requirement exists under § 82.157(j) for ODS and under § 84.106(j) for HFC equipment beginning in 2026.

Step‑by‑step (do the math the “EPA way”)

1. Establish the full charge (manufacturer spec, engineering calc, measured charge, or range midpoint). Document the method.
2. Log every event: pounds added/removed, date, service details. Recordkeeping appears in § 82.157(l) (ODS) and § 84.106(l) (HFCs).
3. Choose your method (annualizing or rolling average) and use it consistently across appliances at a site (limited method‑switch allowance in § 84.106(b)(3)).
4. Calculate the leak rate each time refrigerant is added (exceptions: new install/retrofit/seasonal variance).
5. Compare to the correct trigger (10/20/30% by category).
6. If over the trigger, complete repairs and verification testing within 30 days(or 120 days if an industrial process shutdown is needed). Extensions are allowed with required documentation to EPA.
7. If the appliance leaks ≥ 125% of full charge in a calendar year, submit the annual report by March 1.

Tip (purge exclusion): Purged refrigerant destroyed at ≥ 98% efficiency does not count toward the annual leak‑rate calculation (keep records). § 82.157(k); § 84.106(k).

Repair triggers and applicability at a glance

FAQs

Do automatic leak‑detection (ALD) alarms equal a trigger exceedance?

No. ALD thresholds/alerts (e.g., detect 10 ppm; alert at 100 ppm; or 50 lb/10% “whichever is less” for condition‑based systems) are not the same as the annualized 10/20/30% repair triggers; you still calculate leak rate per the formulas. § 84.108(f)–(h).

Which method should we pick—annualizing or rolling?

EPA allows either, but requires one method per facility (with narrow conditions to switch after acquisitions). Annualizing is sensitive to short‑interval “top‑offs”; rolling smooths the last year (or since last follow‑up test).

Copy‑ready formulas (drop into your SOP)

• Annualizing:

  LeakRate% = (lbs_added / full_charge_lbs) * (365 / MIN(days_since_last_addition, 365)) * 100

• Rolling average:

  LeakRate% = (SUM(lbs_added_last_365_days) / full_charge_lbs) * 100

Citations & further reading (with eCFR links)

• 40 CFR § 82.152 (Definitions) — leak‑rate definition; annualizing/rolling methods; full‑charge methods. eCFR.
• 40 CFR § 82.157 (Appliance maintenance and leak repair) — ODS program (≥ 50 lb): 10/20/30% triggers, 30‑/120‑day repairs, verification tests, extensions, recordkeeping, ≥ 125% annual report due Mar 1. eCFR.
• 40 CFR Part 84 Subpart C (AIM Act HFC Management of Regulated Substances) — overall structure & table of contents. eCFR.
• 40 CFR § 84.106 (Leak repair) — HFC program (≥ 15 lb): 10/20/30% triggers, timing, method consistency/switching, first‑calculation rules for 2026, ≥ 125% annual report due Mar 1, purge exclusion. eCFR.
• 40 CFR § 84.108 (Automatic leak detection systems) — who must install ALD; detection/alert thresholds; how ALD relates to leak‑rate calculations. eCFR.
• EPA overview pages (plain‑English summaries): Stationary Refrigeration Leak Repair Requirements and Regulatory Actions for Managing HFC Use and Reuse; see also the Oct 11, 2024 Final Rule in the Federal Register.