The CARO (Certified Assistant Refrigeration Operator) is RETA's entry-level industrial refrigeration credential. It certifies the knowledge needed to assist with refrigeration system operations under supervision. The exam is 110 questions in English with a three-hour limit, but only 100 active questions count toward your score; 10 pilot questions are being evaluated for future exams. You need 70% of the scored questions to pass. This guide walks you through eligibility, the scored content areas, the onscreen reference system, fees and scheduling deadlines, and a preparation plan based on the official 2026 handbook.
What the CARO credential covers
CARO certifies entry-level knowledge to assist in refrigeration system operations under supervision. Eligibility requires RETA Code of Conduct compliance and a passing score, and the credential is ANAB accredited.
The Refrigerating Engineers & Technicians Association (RETA) issues the CARO as its entry-level operator credential. According to the 2026 CARO Exam Information Handbook, it shows the entry-level knowledge needed to assist in refrigeration system operations under supervision.
Eligibility has two parts, and neither involves prior experience. You must be in compliance with the RETA Code of Conduct, and you must score 70 or higher on the CARO exam. RETA states it may deny, suspend, or revoke certification from anyone who is not in compliance with that Code.
CARO is accredited by ANAB (ANSI National Accreditation Board) as meeting ANSI 17024 standards, which RETA describes as internationally recognized benchmarks often regarded by regulators such as EPA and OSHA.
CARO sits at the base of RETA's credential ladder. The CIRO requires two years of experience plus a passing score, and the CRST requires a current CARO or CIRO, or four years of documented experience, plus its own exam. Holding CARO is therefore one documented route to the CRST, and you can also qualify through experience alone.
Official sources: 2026 CARO Exam Information Handbook (Revision 09), Refrigerating Engineers & Technicians Association — Official RETA candidate handbook PDF, 21 pages
Exam format, scoring and content areas
CARO is 110 questions in English, three hours long, with 100 scored questions and a 70% minimum passing score across ten content areas.
You sit the exam at a proctored test center, and each question appears one at a time on screen. You can answer, skip, or mark a question for review, and you may return to skipped or marked questions at any time. The test ends automatically when time expires. Questions appear in English.
Your score report is emailed after the exam and shows whether you passed, the percentage answered correctly, and section sub-scores. A follow-up report and your certificate arrive by mail from RETA Headquarters.
The exam is based on concepts presented in two RETA texts: Industrial Refrigeration I and Industrial Refrigeration IV (safety section only). RETA notes that other publications introduce the content areas but does not endorse or guarantee that they cover everything tested.
The table shows the scored question counts for the ten content areas. These describe the 100 active scored questions. Ten additional pilot questions, spread across multiple content areas, bring the on-screen total to 110, and those pilot questions are excluded from your score. The handbook also states the outline is supported by refrigeration industry surveys and ongoing reviews by the RETA Certification Committee.
Note that you must surrender any notes you take during the test before leaving the test center.
| Content area | Scored questions |
|---|---|
| Refrigeration fundamentals | 9 |
| Refrigeration cycle | 8 |
| Properties of refrigerants and refrigerant tables | 7 |
| Types of refrigerant compressors | 6 |
| Operation and maintenance of compressors | 14 |
| Lubrication | 10 |
| Evaporators and cooling units | 9 |
| Condensers and high-pressure receivers | 12 |
| Purging | 5 |
| Safety, hazards, and prevention | 20 |
| Total scored | 100 |
Official sources: 2026 CARO Exam Information Handbook (Revision 09), Refrigerating Engineers & Technicians Association — Official RETA candidate handbook PDF, 21 pages
Onscreen references and calculator rules
Reference material appears on screen during the exam, so you cannot bring the study guide in; a simple cleared-memory calculator is allowed.
CARO exams display onscreen references in a PDF next to the test questions. The CARO Study Guide contains exactly the references that appear on screen, and you cannot use the study guide itself during the exam. Treat it the way you would treat operating manuals at a facility: know what each document contains and when to reach for it, because the test will not tell you when to use a reference.
The interface lets you scroll or drag through the reference PDF, zoom in and out, and expand the reference side of the screen. Do not use CTRL+F to search the PDF: the testing system reads that keystroke combination as a security violation and logs you out automatically.
Calculations on this exam require only a simple calculator; a scientific calculator is not needed. Bring a non-printing, non-programmable calculator and expect to clear its memory before entering the testing room. Phone calculators and other devices are not permitted. Not all Kryterion test centers provide calculators, so bring your own.
- References appear onscreen in a PDF next to the questions
- You are never told when to use them; know the documents in advance
- CTRL+F is blocked and triggers an automatic logout
- Simple non-printing, non-programmable calculator only; memory cleared at the door
- No phone or device calculators
Official sources: 2026 CARO Exam Information Handbook (Revision 09), Refrigerating Engineers & Technicians Association — Official RETA candidate handbook PDF, 21 pages
Fees, scheduling and deadlines
The application fee is $570 for members and $865 for non-members, and scheduling goes through RETA, not the test center.
Your application is not complete until all information is provided and fees are paid. Your RETA membership must be current at the time of application to get the member rate, and if your company is a corporate member you must be one of its designated members. Payment can be made online, by phone, or by check or purchase order; note that a test cannot be scheduled until a purchase order has been paid. A returned personal check triggers a $50 fee that must be paid before the exam can be scheduled.
Applications expire one year from the date of payment unless you request a 90-day extension before the end of your eligibility period. If you miss that window, you forfeit your exam fees.
RETA delivers exams through Kryterion Testing Network centers (over 1,000 US locations) and RETA Network Testing Centers. You do not contact the test center directly. Once your application is approved and fees are paid, you schedule by calling RETA Certification Staff at 541-497-2955 on business days between 7:30 am and 4:00 pm Pacific Time, or by emailing certification@reta.org. Be ready to commit to a location, date and time when you call.
After scheduling, RETA emails you a test authorization code. The proctor cannot start your exam without it, so print the email and bring it. You must also present two forms of identification, with at least one government-issued photo ID such as a driver's license or passport, and the second ID must carry a matching signature. Report to the test center 15 to 20 minutes early.
Deadlines matter. Reschedule at least four business days (96 hours) before your test date; rescheduling inside that window costs a $150 processing fee. If you fail to show without rescheduling at least four business days ahead, you forfeit all fees. If you withdraw at least five business days before the test, you may request a refund of up to half the application fee. Registrations cannot be transferred to another candidate.
If you do not pass, you may retest once at two-thirds of the fee within one year of your initial test: $380 for members or $580 for non-members. You submit a new application and fee, at least two weeks must pass between sessions, and you have 90 days after approval and payment to schedule and complete the retest. A third attempt costs full price. You can appeal exam results in writing to RETA Headquarters within 14 calendar days of your exam date.
Official sources: 2026 CARO Exam Information Handbook (Revision 09), Refrigerating Engineers & Technicians Association — Official RETA candidate handbook PDF, 21 pages
How to prepare for the CARO exam
Study Industrial Refrigeration I and the safety section of Industrial Refrigeration IV, download the free CARO Study Guide, and use the practice test included with your application.
RETA's official path starts with two texts: Industrial Refrigeration I, and the safety section of Industrial Refrigeration IV. The handbook also lists alternate references and training options, from Stoecker's Industrial Refrigeration Handbook to TPC Training Series titles on ammonia refrigeration basics and electrical troubleshooting, while cautioning that completing a course or reviewing materials does not guarantee a passing score.
Download the free CARO Study Guide from the RETA website. It shows the references that appear on screen during the exam, so use it to learn what each document contains and where to find answers. You cannot bring it into the test.
One practice test is included in your application fee, and details arrive at the email address on your application. Additional practice attempts cost $59 each. Practice questions resemble the full exam and use the same onscreen references. Book tests, sold through the RETA store at $25 per attempt, verify course completion and can earn Professional Development Hours toward recertification rather than serving as exam prep.
For broader themes, use the handbook's outline as your map. Safety, hazards and prevention is the largest scored area at 20 questions, so give the safety section of Industrial Refrigeration IV proportional attention. The published outline does not break ammonia safety or electrical controls out as separate scored areas, so let the free Study Guide and the two named RETA texts set your priorities rather than unofficial topic lists.
Label this next part as advice rather than a requirement: you may find it useful to rehearse navigation, not just content. Practice moving through the reference PDF quickly, since you are never told when to use it, and remember that CTRL+F will log you out of the test.
- Study Industrial Refrigeration I and the safety section of Industrial Refrigeration IV
- Download the free CARO Study Guide and learn its reference documents
- Take the practice test included with your application; extra attempts cost $59
- Consider alternate references from the handbook's list if you prefer non-RETA materials
- Bring a simple non-programmable calculator and two forms of ID on test day
Official sources: 2026 CARO Exam Information Handbook (Revision 09), Refrigerating Engineers & Technicians Association — Official RETA candidate handbook PDF, 21 pages
After you pass: renewal in brief
Your credential lasts three years and you can renew by documenting 24 PDHs or by retaking the current exam.
Each RETA certificate expires three years after it is issued. You can renew either by retaking the current exam or by documenting your qualifications, and CARO recertification requires 24 Professional Development Hours relevant to refrigeration practice. One PDH equals 50 minutes of instruction or participation, and one continuing education unit equals 10 PDHs. PDHs must be dated during your active certification cycle, and renewals cannot be requested more than six months before the expiration date.
If your credential lapses, you must retest; expired credentials cannot be renewed with PDHs. Documentation goes into RETA's Recertification Database, and the Appendix 500-B PDH table on the RETA website lists training activities and their PDH values.
Official sources: 2026 CARO Exam Information Handbook (Revision 09), Refrigerating Engineers & Technicians Association — Official RETA candidate handbook PDF, 21 pages
Final checklist before test day
Work through the handbook's application checklist and confirm application, fees, scheduling, ID, calculator and authorization code are all in place.
RETA publishes a CARO Application Checklist, and the items below follow it. Complete the online exam application at reta.com under the certification tab and pay the fee; sign in to your own account first if you qualify for the member rate. Download the free CARO Study Guide for your exam and review it carefully, then take your practice exam.
Locate a test center on the RETA website, but schedule through RETA Certification Staff rather than calling the center. Once scheduled, print the email containing your test authorization code; the proctor cannot start your exam without it.
On test day, arrive 15 to 20 minutes early with two forms of identification, at least one government-issued photo ID, and a simple non-programmable calculator with its memory cleared. Do not use CTRL+F in the onscreen references during the exam, and remember that notes taken during the test must be surrendered before you leave.
- Submit the online application and pay the fee before the one-year window closes
- Download the free Study Guide and take the included practice test
- Schedule by phone or email through RETA, not the test center
- Bring the authorization code email, two IDs and a cleared-memory simple calculator
- Arrive 15 to 20 minutes early
- Leave notes with test center staff before departing
Official sources: 2026 CARO Exam Information Handbook (Revision 09), Refrigerating Engineers & Technicians Association — Official RETA candidate handbook PDF, 21 pages
Official sources
Facts checked against the 2026 CARO Exam Information Handbook: