What organization certifies technicians to handle refrigerants?

The concept behind this question

Section 608 splits technician certification by the equipment you work on: Type I for small appliances, Type II for high-pressure systems, Type III for low-pressure systems, and Universal for all three. Core is mandatory for every certification and covers the material common to all of them. Certification does not expire. The regulations also govern leak repair thresholds, recordkeeping, and the disposal and final-venting requirements that apply when equipment reaches end of life.