The Complete Subpart C Field Reference: Every Threshold, Deadline, and Requirement on One Page

On January 1, the 15-pound threshold went live. Since then, we've covered every major aspect of Subpart C: how to calculate leak rates, which rules actually got enforcement relief, documentation standards, the 30-day repair workflow, building owner conversations, the 125% chronic leaker rule, and which systems are actually covered.

This post puts all of it in one place.

Print this. Laminate it. Put a copy in every truck and tape one to the wall in your office. This is the reference your techs reach for on every service call for the rest of the year.

Section 1: Is This System Covered?

Step 1 — Refrigerant type:

Rule: If the refrigerant contains an HFC listed in appendix A to part 84, Subpart C applies whatever the blend's GWP; a non-HFC substitute is covered only if its GWP is greater than 53 (§ 84.106(a)). If it contains solely an ODS → Section 608. If it is a natural refrigerant (GWP of 53 or less) → neither.

Step 2 — Charge size:

• Less than 15 lbs → Not covered by Subpart C
• 15 lbs or more → Continue to Step 3

Step 3 — System type:

Section 2: Leak Rate Calculation Methods

The owner or operator must calculate the leak rate every time refrigerant is added to a covered system, unless the addition immediately follows a retrofit or new installation, or itself qualifies as a seasonal variance (§ 84.106(b)). The same method must be used for all appliances at a facility (§ 84.102).

Method 1: Annualizing

Leak Rate = (Lbs Added ÷ Full Charge) × (365 ÷ Days Since Last Addition, capped at 365) × 100

• Projects the current leak forward over a full year
• If more than 365 days have passed since the last addition, use 365 — the rule takes the shorter of the two (§ 84.102, "Leak rate", Step 2)
• For the first calculation after January 1, 2026, substitute 365 for "Days Since Last Addition" (§ 84.106(b)(1))
• Produces higher results when the interval between additions is short

Method 2: Rolling Average

Leak Rate = (Total Lbs Added in the Last 365 Days* ÷ Full Charge) × 100

• *Or since the last successful follow-up verification test showing all identified leaks were repaired, if that was less than a year ago (§ 84.102, "Leak rate", rolling average Step 1)
• Looks backward at the past year of actual additions
• For the first calculation after January 1, 2026, use total lbs added since January 1, 2026 (§ 84.106(b)(2))
• Smooths out spikes but may undercount early in the tracking period

Section 3: What to Record on Every Service Call

When refrigerant is added to a covered system, document all of the following:

Retention: All records must be kept for at least 3 years in electronic or paper format (§ 84.106(l)) — and the appliance's own file (owner and address, full charge and how it was determined, any revisions, installation date) until three years after the appliance is retired (§ 84.106(l)(1)). Retrofit/retirement plans and extension requests must additionally be kept accessible at the site, in paper or electronic form, for EPA inspection on request (§ 84.106(h)(3), (i)).

Section 4: Repair Workflow When a Threshold Is Exceeded

Ongoing inspection schedule after threshold exceedance:

If the repair does not bring the leak rate below the threshold:

Extensions (30-day repair) — only if you file:

• Request it from EPA electronically within 30 days of the exceedance (120 with an industrial process shutdown), signed by an authorized company official — after completing and verifying, within that window, the repairs to significant leaks that don't need extra time, and documenting why the rest can't be done in time (§ 84.106(f), (f)(2)–(4))
• Grounds: components unavailable → up to 30 days after delivery, max 180 days from the exceedance (270 with an industrial process shutdown); conflicting federal, state, local, or tribal rules → as needed; radiological contamination → as needed (§ 84.106(f)(1))
• An industrial process shutdown makes the starting window 120 days instead of 30 — that is the base deadline under § 84.106(d), not an extension
• Not valid: "Certified technician unavailable"

Section 5: Chronic Leaker Rule (125%)

Formula:

Calendar-Year Loss = (Lbs of Refrigerant Leaked Jan 1–Dec 31 ÷ Full Charge) × 100

The rule counts refrigerant leaked in the calendar year (§ 84.106(j)), not every pound added. Purged refrigerant destroyed at a verifiable 98% efficiency or better doesn't count toward the leak rate (§ 84.106(k)), and an addition that isn't replacing lost refrigerant — a new installation's charge, a qualifying seasonal-variance addition (§ 84.102) — isn't leakage. The report lists the annual percent loss and the amounts added as separate items (§ 84.106(m)(4)).

If result ≥ 125%: System is a chronic leaker. Report to EPA by March 1 of the following year.

What the report must include (§ 84.106(m)(4)):

• Owner/operator, facility name and address, appliance ID or description
• Appliance type (comfort cooling or other, industrial process refrigeration, or commercial refrigeration)
• Refrigerant type and full charge (lbs)
• Annual percent refrigerant loss
• Dates and amounts of each refrigerant addition
• Date of the last successful follow-up verification test
• Explanation of the cause of the losses and description of repair actions taken
• Whether a retrofit/retirement plan has been developed and, if so, the anticipated date
• Signed statement from an authorized company official

Section 6: Key Dates

Section 7: Penalty Reference

Section 8: The Five Numbers Every Tech Needs Before Leaving the Site

Every time your tech adds refrigerant to a covered system, they should not leave the site without recording these five numbers:

That's it. Five numbers. Thirty seconds. Those five data points feed the leak rate calculation, determine whether a repair is triggered, and accumulate toward the chronic leaker threshold. If any one of them is missing, the compliance chain breaks.

How to Use This Guide

For owners and office managers: Use Sections 1, 5, and 6 to understand which of your customer's systems are covered, when reports are due, and what dates to watch. Section 4 is your workflow when a tech calls in a threshold exceedance.

For technicians in the field: Use Sections 1, 2, 3, and 8 on every service call. Three questions to determine coverage, two formulas for the calculation, a checklist for what to record, and five numbers to capture before you drive away.

For building owner conversations: Use Sections 4, 5, and 7. The repair timeline, the chronic leaker consequence, and the penalty numbers are the three things that make building owners pay attention.

Every Subpart C requirement, distilled to one page. The contractors who put this in every truck are the contractors who won't be scrambling when the first audit letter arrives.

Start Here by Topic

This reference is the hub. When one line item here becomes your problem, each topic has an anchor post that goes all the way down:

• Calculating leak rates → How to calculate refrigerant leak rates under the new EPA rules — both approved methods, worked examples, field guide format.
• A leak rate came back hot → The complete repair workflow under Subpart C — the 30-day clock, verification tests, and every exit from the standard path.
• The 125% report → How a "small leak" becomes a federal report to the EPA — the chronic-leaker rule and the March 1 deadline.
• Surviving an inspection → What an EPA inspection actually looks like — your records as an audit defense.
• The AIM Act transition → The 15-pound rule and what it started — the rule that put HFC appliances of 15 lbs or more under leak-repair requirements (residential and light commercial AC and heat pumps excepted).
• Who is responsible → Owner or contractor — who does the EPA actually fine? — where each duty lands between owner, operator, contractor, landlord, and tenant.
• Beyond the federal floor → State refrigerant rules that could catch you off guard — where CARB-style overlays stack on top of Subpart C.

---