CARO is the foundation. CIRO is the advanced credential. Both are issued by RETA — the Refrigerating Engineers and Technicians Association, founded in 1910 and now merged with RSES — and they are the only industrial refrigeration certifications in the country accredited by ANSI. Whether you are an employer deciding what to require or a technician deciding what to earn, these are the two certifications that matter.
Why They Exist
On October 25, 2026, a fire broke out at Pacific Seafood's plant in Newport, Oregon. The city evacuated everyone within a mile — not because of the fire, but because of the ammonia. The tanks held and no one was hurt. But the evacuation itself tells you everything about what this chemical is.
Ammonia is toxic. In high concentrations it can be explosive. Refrigeration systems run under pressure at temperatures that will cause severe chemical burns on contact — ammonia boils at roughly −28°F and is intensely attracted to water, which means it finds your eyes, your lungs, and your skin first. The difference between a person who understands that and a person who thinks he does is, in the worst case, the difference between life and death.
For most of the industry's history, people learned on the job. A senior operator showed you how the system worked, and over the years you figured it out. Before about 1995, that was essentially the only path. RETA's certification programs were built to solve the problem that created: how do you know, with real confidence, that the person running your system truly understands it?
Certificate Versus Certification
This is a distinction most people miss, and it matters a great deal.
Training schools — good ones, like the Garden City Ammonia Program and Linear Technical Services — award a certificate when you finish a course and pass its test. That certificate says you learned a body of material. It is worth something.
A RETA certification is different. It is a living credential. The exams are accredited by ANAB under the ANSI standard, meaning the testing process is independently regulated: the questions are validated, the proctoring is secure, and only someone who genuinely understands the material can pass. Once certified, you maintain it with continuing education and renew every three years. It does not sit in a drawer. It stays current, or it expires.
For employers, the difference is not academic. OSHA's Process Safety Management standard — 29 CFR 1910.119(g) — requires documented training for every employee involved in operating a process that handles highly hazardous chemicals, including anhydrous ammonia above 10,000 pounds. Refresher training is required at least every three years. A course certificate satisfies the letter of that rule. A RETA certification satisfies it and then some: it is independent, it is accredited, and it provides a stronger basis for demonstrating due diligence. If something goes wrong and regulators ask whether you did everything you should have, hiring and supporting RETA-certified operators is one of the strongest answers you can give.
What CARO Covers
CARO — Certified Assistant Refrigeration Operator — is the entry-level credential. There is no minimum experience requirement, and the exam is 110 questions over three hours.
It covers the fundamentals: the history of mechanical refrigeration, basic thermodynamics, heat-load calculations, the types of refrigerants and how they behave, the pressure-temperature relationship, and the major components of a refrigeration system.
Some people say the CARO is too heavy on the engineering. For a while I thought the same thing. But after spending more time with the material, I understood it differently. The engineering is not filler. It gives you a real understanding of what is actually happening inside the system — and when you understand that, you understand what your job is and how to do it safely. Everyone in industrial refrigeration should have a CARO. It is the floor.
What CIRO Covers
CIRO — Certified Industrial Refrigeration Operator — requires documented experience in industrial refrigeration, and it is not simply a harder version of the same test.
CIRO is a different level. Here you learn how real systems are piped — pump-circulated, gravity-fed, pumper-drum systems, and other configurations. You learn to diagnose what is happening inside a system by reading what the control panel tells you: voltage and amperage from the motors, pressures and temperatures at different points. You learn to see problems before they become emergencies.
It is a serious, challenging certification. If you earn it, companies will look at you differently. A technician with three or four years of experience and a CIRO will command the same pay as someone with ten or more years without one. That is not a guess — it is what I see in the searches I run every week.
The Numbers That Explain Everything
The last time I spoke with RETA, roughly 1,700 people in the United States held any type of RETA certification. The industry employs approximately 35,000. That is about five percent.
Five percent is an abysmally low number, and it needs to change. But it also explains a tension every employer in this space has felt: certification should be a standard requirement, and one day we hope it will be. Today, requiring it means your candidate pool drops to one person in twenty. That is the math.
It does not mean you should not value it. It means you should understand what you are asking for when you write the job description. The smarter path for most employers is to hire for real experience, prefer candidates who hold a CARO or CIRO, and commit to sponsoring the certification after the hire. You get a wider pool now and a certified operator later — and the person you hire sees that you take the work seriously, which matters more than most companies realize.
If You Work in This Industry
Whether you are brand new or you have thirty years in the business, if you do not have your RETA CARO or CIRO, it is time to get one.
Get both. Start with the CARO — it builds the foundation. Then earn the CIRO when you have the experience. Each one raises your understanding of the systems you work on every day. There are no downsides. Only upsides: more money, more career options, and companies calling you every week with strong offers.
Talk to your company. If they are not willing to pay for it, I would pay for it myself. It is worth it.
If you are struggling to find a company that will sponsor your certification, call me directly. I will connect you with a company that would be happy to pay for it.
How NH3 Jobs Helps
For employers: Post your ammonia job free on NH3 Jobs. Every posting includes a market analysis so you can see how your pay and requirements compare. When the position has to fill now, Jennifer, our AI recruiter, runs a 30-day outbound campaign for $1,499 — she takes your job to the best 50 fits near your plant and sends you the ones who want to interview. See how it works.
For technicians and operators: Browse open positions or upload your résumé and let us bring the right jobs to you.