EPA 608 · Core, Type I, Type II, Type III
Practice questions that explain every miss. Pick the wrong answer and Certain tells you why that one was wrong, not just which one was right.
Free with ads. $4.99 removes them for good. No account, no subscription.
Which of these refrigerants is a Class I ozone-depleting substance under Section 608?
R-22 is an HCFC, so it is Class II. Class I is the CFC family: R-11, R-12, R-500, R-502. The rule of thumb: chlorine plus hydrogen is Class II, chlorine without hydrogen is Class I.
The whole idea
Most prep apps show you the right letter and move on. Certain writes a short explanation for the exact wrong choice you made, in plain language, the moment you make it. That is the thing the exam actually tests: knowing why the tempting answer is wrong.
Every miss comes back on a schedule until you have answered it correctly three times in a row. Then it stays gone.
First return. Same question, fresh eyes.
Second pass, mixed into practice.
Three correct in a row and it is known.
How it works
Core, Type I, Type II or Type III, one question at a time. Readiness shows how much of the bank you already know.
The explanation is written for your wrong choice. Fifteen seconds of reading, never a wall of text.
Misses return at 1, 3 and 7 days. When your exam date is set, the countdown and readiness sit on the Study tab.
Exams
Universal certification. Most people pass above 80%.
Available nowCivics interview. You need 12 of 20.
Coming soonFAA remote pilot. 60 questions, 70% to pass.
Coming soonTechnician license. 26 of 35 to pass.
Coming soonPricing
The full question bank, the mock exam, every explanation and backup are free for everyone. A small banner sits under the tabs and one full-screen ad shows at the end of a session, never mid-question. If you would rather not see them, one purchase removes them from that app forever.
Everything
Questions
Yes. Ads pay for it. Nothing in the app is locked behind the $4.99 purchase except the ads themselves.
No. The app works the moment it opens. Your progress is backed up under an anonymous id so a reinstall can restore it.
Written for Certain against the current EPA Section 608 rules and the four exam sections. Not copied from a prep book, and not the test itself.
Practice, review and the mock exam all run on the phone. Explanations for new misses need a connection the first time.