The Refrigerating Engineers and Technicians Association (RETA) offers certifications for different levels of industrial competency. The RETA awards these certificates after passing the examination for the certificate in question. The two levels of certification are the CARO (Certified Assistant Refrigeration Operator) and the CIRO (Certified Industrial Refrigeration Operator). The former certifies that an individual is able to safely conduct himself in industrial settings under appropriate supervision, while the latter certifies that an individual is capable of safely conducting himself in industrial environments while safely supervising subordinates.

Go to the RETA website to download your application to take the exam. The application document will contain additional information about the exam itself and testing procedures. Use this information to anticipate what the exam environment will be like as you study.

Download the "Supplemental Package" for the exam you are preparing to take (either the CARO or the CIRO) from the RETA website. This will include the formulas and data tables you must be familiar with when you sit the exam.

Study the formulas and data in the supplemental package. While you will not need to memorize all the formulas, you should be familiar with them by the time you take the exam.

Download and study other review notes and preparation guides posted on RETA's website. These will review the major concepts of the exam, and often include sample questions with which you can practice. If you feel you need additional preparation, proceed to the next step.

Enroll in a RETA certification training course for the certification you are seeking. These classes provide you with training and practice for the exam you are looking to sit. Most classes cost money, and do not make any guarantees about you passing the RETA exam after completing their course, so make sure you pay attention if you want your money's worth.