PT Charts
Pressure–temperature charts, a superheat and subcooling calculator and original EPA 608 practice tests, built from CoolProp and 40 CFR Part 82.
Working superheat or subcooling?
Enter both line pressures and temperatures; it reads the dew point for superheat and the bubble point for subcooling.
Open the superheat and subcooling calculatorPT Charts is a free reference for HVAC/R work. It has pressure–temperature charts for five refrigerants, a superheat and subcooling calculator, and original practice tests for the EPA 608 exam. The chart rows are computed with CoolProp, and every practice question is written from the regulation text it cites, so each figure and answer can be traced back to where it came from.
Charts
EPA 608 practice
EPA 608 Core Practice Test: 25 Original QuestionsTwenty-five original EPA Section 608 Core practice questions written from 40 CFR Part 82, with the answer, explanation and regulation cited for each.
EPA 608 Type II Practice Test: 25 Original QuestionsTwenty-five original EPA Section 608 Type II practice questions on who needs Type II and the leak-repair rules, each with its regulation cited.
Guides
Reading the charts
Which PT Chart Do I Need? A Refrigerant Routing TableOne routing table to find the right refrigerant chart, plus which saturation point to read for superheat and which for subcooling.
What EPA's A2L Listing Means for R-454B and R-32What changed when EPA's SNAP program listed R-454B and R-32 as A2L, which of this site's five refrigerants that covers, and what it doesn't tell you.
Rules on the job
Refrigerant Leak Repair: Which EPA Rule Applies?Two separate EPA leak-repair rules cover refrigerant appliances: 40 CFR 82.157 for ozone-depleting refrigerants and the 2024 AIM Act rule for HFCs.
Recovery, Reclaim and Cylinders: The 2024 AIM Act ChecklistThe 15% virgin-HFC cap on reclaimed refrigerant, which sectors must service with reclaimed HFCs by 2029, and what to do with disposable cylinders.
R-22 and the HCFC Phase-Out: What's Left to KnowThe Clean Air Act's HCFC phase-out timeline through 2030, where R-22 sits on EPA's class II list, and the service, retrofit or replace decision.
EPA 608 study
EPA 608 Certification Types: Type I, II, III and UniversalWhat EPA Section 608's four certification types cover, how each test is built and graded, and the mail-in option for Type I.
What Each EPA 608 Test Covers: A Study Checklist by GroupA group-by-group study checklist for the EPA 608 core and technical questions, plus the areas this site's saved regulation text doesn't reach.
How the numbers are computed and checked, and how the questions are sourced, is on the methodology page.