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

Nine weeks ago, 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 has a GWP > 53 and is an HFC → Subpart C applies. If ODS only → Section 608. If natural refrigerant → 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

You must calculate the leak rate every time refrigerant is added to a covered system, except immediately following a new installation, retrofit, or seasonal variance. You must use the same method for all appliances at a facility.

Method 1: Annualizing

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

• Projects the current leak forward over a full year
• For the first calculation under Subpart C, substitute 365 for "Days Since Last Addition"
• Produces higher results when the interval between additions is short

Method 2: Rolling Average

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

• Looks backward at the past year of actual additions
• For the first calculation under Subpart C, use total lbs added since January 1, 2026 (or last successful follow-up verification test)
• 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 a minimum of 3 years in electronic or paper format. Records must be accessible at the site and available for EPA inspection.

Section 4: Repair Workflow When a Threshold Is Exceeded

Ongoing inspection schedule after threshold exceedance:

If repair fails within 30 days:

Extension grounds (30-day repair):

• Components unavailable → up to 30 days after delivery, max 180 days total
• Regulatory conflict → as needed
• Industrial process shutdown required → 120 days instead of 30
• Not valid: "Certified technician unavailable"

Section 5: Chronic Leaker Rule (125%)

Formula:

Calendar Year Leak Rate = (Total Lbs Added Jan 1–Dec 31) ÷ Full Charge × 100

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

What the report must include:

• Owner/operator and facility identification
• Appliance ID, type, and location
• Full charge and refrigerant type
• Calendar year leak rate and total lbs added
• Description of all leak identification and repair efforts
• Whether a retrofit/retirement plan exists
• Signed statement from authorized 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.

Nine weeks of regulation, 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.

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This wraps up our initial Subpart C series. Over the past nine weeks, we've built a complete knowledge base — from the rule itself through calculations, documentation, repairs, business strategy, chronic leaker tracking, and system coverage. Every post is linked in the archive and cross-referenced for the topic you need.

The blog continues every Monday. Coming up: seasonal variance rules, the reclaimed refrigerant standard, how state rules layer on top of Subpart C, and field stories from contractors navigating compliance in the real world. We'll see you next week.