Paul Gunder
Paul Gunder builds calculators and reference tools at Rocky Mountain Apps. For PT Charts, he computed the pressure–temperature charts with CoolProp and wrote the EPA 608 practice questions from the regulation text, with a test that checks each quoted passage against the saved source.
He's a software builder, not an HVAC technician. The methodology page explains how the charts and questions are made and checked.
Written by Paul Gunder
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.
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.
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.
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.
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.
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.