They each cost money. Not exorbitant though.
609 is pretty easy. Open book, online. I took it through MACS.
608 is more challenging. Not open book. Must be done in person at a testing site. Can be done online via ProctorU (for example), but the online proctor watches you take the exam and inspects your test site (all via camera) to eliminate cheating.
I did testing via ProctorU for convenience. Used a laptop and took it early in morning at kitchen table while family was sleeping so no one came into the room.
The 608 license was provided from Esco Institute immediately after passing the test (benefit of doing it online).
I studied hard for about a month. Studied the CFR (federal law), a 608 PDF from Esco Institute, and also iPhone 608 app. Nearly aced it. Missed a couple questions max from each section — results below:
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Test is 4 sections (Core, Type I, Type II, and Type III), 25 questions each. It goes over residential, commercial, and industrial HVAC. MVAC is not covered under 608, as it is covered under 609.
If you pass all 4 sections of the 608 examination, you get EPA 608 Universal license.
A 608 license does not license you to perform repairs on other peoples' HVAC system. You still need your state's HVAC contractor license for that. It just allows you to buy the refrigerant (e.g., R-22, R-410a, etc.).
609 does allow you to perform MVAC repairs on other peoples' MVACs and buy the refrigerant, as I do not know of any state that requires MVAC repair persons (e.g., auto techs) to have a state license.
You don't need either license to work on your own system, but you do need them to buy the refrigerant.
I don't plan on working on anyone else's HVAC. Just needed the licenses to purchase refrigerant.