By Priya Raman · Updated October 2, 2026 · 5 min read
Short answer
TDLR adopted the 2024 editions of the International Mechanical Code, Uniform Mechanical Code and related codes, with the rule chapter effective September 1, 2026. TDLR cited federal refrigerant rules requiring A2L refrigerants, which the 2021 editions do not cover. Cities and counties still adopt and enforce their own codes, so Austin and Dallas can differ. Verify the effective dates and local amendments before design or permit work.
In 2026 Texas moved its air conditioning and refrigeration rules to the 2024 editions of the model mechanical codes. TDLR published the adoption in the Texas Register on August 28, 2026, and the updated rule chapter is reported to take effect September 1, 2026. TDLR said the reason for moving faster than its usual cycle was federal refrigerant rules that require A2L refrigerants, which the 2021 codes do not address. This is general information, not legal advice; confirm the adopted text and transition rules with TDLR and your local building department.
What did Texas adopt?
Reports on the adoption list the 2024 International Residential Code, International Mechanical Code, International Fuel Gas Code and the 2024 Uniform Mechanical Code, replacing the 2021 editions. Trade press says the Uniform Mechanical Code edition is the one referenced for ACR contractors under TDLR rules. Which code applies to a given job also depends on the local jurisdiction, so read both state and local requirements.
Why was it done now?
The federal American Innovation and Manufacturing (AIM) Act is moving equipment to lower-GWP refrigerants. Many of them are A2L, which are mildly flammable. The older codes do not include installation and service rules for A2L refrigerants, so technicians and inspectors had no clear code basis. The 2024 editions add provisions for them. For background, read A2L refrigerants explained and what is changing in 2026.
What changes in practice?
| Area | Likely effect of the 2024 editions |
|---|---|
| A2L systems | Defined rules for charge limits, leak detection, ventilation and ignition sources |
| Equipment listing | Equipment must be listed for the refrigerant and installed per manufacturer instructions |
| Inspections | Inspectors use the new code text when reviewing permits |
| Exams and training | Exam references and training materials are updated to the adopted editions |
| Plan review | Designers refer to the 2024 sections for refrigerant safety and machinery rooms |
The details differ by section and by local amendment. Do not assume that a rule from the model code applies unchanged in your city.
Do Austin and Dallas follow the same code?
Not necessarily. State adoption sets a baseline for TDLR matters, but cities and counties adopt and amend building and mechanical codes through their own processes. One report on the adoption says Dallas enforces a code based on the 2021 International Mechanical Code while Austin uses the 2024 Uniform Mechanical Code. Dates and amendments change, so call the local building department or check its adopted codes page before you design or permit a job.
What should chiller and refrigeration teams do now?
- Get the text. Read the adopted TDLR rule chapter and the model code sections for refrigeration systems and machinery rooms.
- Check local amendments in the city or county where the work happens.
- Update procedures. Add A2L handling, leak detection checks and ignition-source control to checklists.
- Confirm training. Make sure technicians have current EPA Section 608 certification and manufacturer A2L training.
- Plan equipment. New chillers and packaged units with A2L refrigerants may need machinery-room or leak-detection provisions; ask the manufacturer for the installation manual.
- Watch the effective date and transition language. I could not confirm what grandfathering applies to permits filed before the effective date.
What does it mean for exams?
TDLR exam reference lists have historically named both the UMC and IMC. A third-party study guide says the 2024 editions take effect for the exam on September 1, 2026, but that is not an official source. Check TDLR’s exam page. If you are preparing, see how to get a Texas Class A HVAC/ACR license.
How do the codes affect design and documentation?
Code adoption shows up in everyday work in a few predictable places.
- Refrigerant safety. Systems using lower-GWP refrigerants may need attention to charge limits, ventilation and leak detection; the background is in A2L refrigerants explained and RTU basics and the A2L transition.
- Machinery rooms. Ammonia and large-charge plants have additional expectations; see ammonia refrigeration system basics and IIAR 2 and IIAR 6 standards.
- Local amendments. Cities can adopt amendments, which is why Austin and Dallas differ. Always confirm with the local building department.
- Plan review. Drawings and equipment schedules should state refrigerant type, charge and safety class so reviewers can verify compliance.
Keep a copy of the adopted code edition with the job file, and verify what applies to a specific project with the authority having jurisdiction and tdlr.texas.gov.
Frequently asked questions
Does the new code affect existing equipment?
Codes usually apply to new installations and alterations, not to equipment already in place, but local rules vary. Ask the local building department.
Do the 2024 codes ban R-410A?
No. Codes govern installation, not refrigerant production. Federal rules limit the refrigerant in new equipment; see the EPA Technology Transitions pages.
Where can I read the TDLR adoption notice?
In the Texas Register and on TDLR’s rulemaking news pages, linked below.
We follow these rules closely because we plan to enter the Central Texas market. If you work with Texas contractors, suppliers or shops and want to talk, see our partnership options.
