Images used in practice questions
Some practice questions in HVAC Exam Prep 2026: EPA 608 include diagrams and photographs from Wikimedia Commons. Each image is listed below with its author and license, linked to its source page. Images were resized and converted to JPEG for display in the app; no other changes were made. Images under Creative Commons ShareAlike licenses remain available under the same license. The authors do not endorse this app.
- Atmosphere layers-en.svg — NOAA & User:Mysid — Public domain
- Ozone depletion.png — Saranit gade — CC BY-SA 4.0
- Atmospheric ozone.svg — Rastrized and improved by RedAndr — Public domain
- HCFC and HFC atmospheric trends.png — James W. Elkins and Stephen A. Montzka — Public domain
- 1,1,1,2-Tetrafluoroethane.svg — The original uploader was Sbrools at English Wikipedia. — Public domain
- Global warming potential.png — Sorbot — CC BY-SA 3.0
- Kigali Amendment to the Montreal Protocol ratification map.svg — Delusion23 — CC BY-SA 4.0
- Refrigerator-cycle.svg — Original source file: Ilmari Karonen
Original uploader was Keno at en.wikipedia.
Later version(s) were uploaded by Hom — GFDL
- Refrigerator-cycle1.svg — Kaboldy — CC BY-SA 3.0
- RefrigerationTS.svg — derivative work: Gagea (talk)
RefrigerationTS.png: Original uploader was Keenan Pepper at en.wikipedia — CC BY-SA 3.0
- RefrigerationTS.png — The original uploader was Keenan Pepper at English Wikipedia. — CC BY-SA 3.0
- 2d scroll-compressor.svg — Kbentekik — Public domain
- P-V compressore alternativo.svg — A7N8X — CC BY-SA 3.0
- Compressore alternativo pv.png — see source page for author — CC BY-SA 3.0
- Rotary vane.png — No machine-readable author provided. Ub assumed (based on copyright claims). — CC BY-SA 3.0
- Heat exchanger types.PNG — Hondrej — Public domain
- Straight-tube heat exchanger 2-pass.svg — Sandstorm de — CC BY-SA 4.0
- Absorption refrigerator working.svg — Goran tek-en, following request by Gem fr — CC BY-SA 4.0
- Absorptive refrigeration.svg — Bilious at English Wikipedia — Public domain
- Mollier diagram.svg — Maxinvestigator — CC BY-SA 4.0
- Mollier enthalpy entropy chart for steam - US units.svg — emok (talk) — CC BY-SA 3.0
- CoolingTower.png — User:mbeychok — CC BY-SA 3.0
- Evaporative cooler air exchange.svg — Nevit — CC BY-SA 3.0
- VRF System Concept (Multi Split System air conditioner).jpg — Nilsonsvidal (talk · contribs) — Public domain
- Geothermal Systems.jpg — Marktj at English Wikipedia — Public domain
- Phase change heat pump.svg — Original: Jleedev Vector: gringer — CC BY-SA 3.0
- HeatAndColdStorageWithHeatPump.svg — HeatAndColdStorageWithHeatPump.jpg: KVDP
derivative work: Fred the Oyster — CC BY-SA 3.0
- Series Operated Solar Heat Pump diagram.svg — KCVelaga — CC BY-SA 4.0
- Solar water heating schema.svg — Original: Strug Vector: Malyszkz — CC BY 2.5
- Electrical VFD Diagram, 2phase to 3phase.svg — Orion Lawlor — CC0
- Simple electrical schematic with Ohms law.svg — Mehanik — CC BY-SA 3.0
- Psychrometric chart.png — en:User:ArthurOgawa — Public domain
- Processes on the Psychrometric chart.png — IanVG — CC0
- PsychrometricChart.SeaLevel.SI.svg — ArthurOgawa — CC BY-SA 3.0
- Dry-bulb lines-IP-Wiki format.svg — IanVG — CC0
- Humidity lines-SI-Wiki format.svg — IanVG — CC0
- Vapor pressure of H2O.png — GeSciHok — CC BY-SA 4.0
- Rooftop Packaged Units.JPG — P199 — Public domain
- Aging Condenser Unit of a Split Air Conditioning System (7547606426).jpg — Chris Hunkeler from Carlsbad, California, USA — CC BY-SA 2.0
- Temperature-entropy chart of a superheated Rankine cycle.svg — Olivier Cleynen — CC0
- Earth's atmosphere.svg — Kelvinsong — CC BY-SA 3.0
- Compressor, vacuum pump, reciprocating piston type (ISO 10628-2).svg — ChemSim — Public domain
- Ozone depletion cropped.png — Mrfoogles — CC BY-SA 4.0
- CFCs & Ozone.jpg — Nicole Leihe — CC BY-SA 4.0
- Thermostatic expansion valve.svg — MasterTriangle12 — CC BY-SA 4.0
- Moisture indicator.svg — Andrew.wittkamper — CC BY-SA 3.0
- R407C lin.png — Jzana — CC0
- Log ph Diagram.png — TLK Energy GmbH — CC BY-SA 4.0
- Scheme of combined absorption and vapor-compression refrigeration system.png — Frederick Alexander Costello — Public domain
- Pond Loop Close Up.jpg — Mark Johnson (Marktj at English Wikipedia) — Public domain
- U-tube heat exchanger.svg — Sandstorm de — CC BY-SA 4.0
- Ozone destruction Cycle.svg — Ross J. Salawitch (Lead Author), David W. Fahey, Michaela I. Hegglin, Laura A. McBride, Walter R. Tribett, Sarah J. Dohe — Public domain
- Montreal-protocol-organisation en.svg — DeWikiMan — CC BY-SA 4.0
- Nh3 ph en.png — Jzana — CC BY-SA 3.0
- Schematic representation of a basic hybrid absorption–compression heat pump cycle.png — Marcel Ulrich Ahrens, Maximilian Loth, Ignat Tolstorebrov, Armin Hafner, Stephan Kabelac, Ruzhu Wang and Trygve Magne Ei — CC BY 4.0
- Cascade refrigeration (two-cycle) process schematic diagram.svg — LBuwBsCY15V$ — CC BY-SA 4.0
- RefrigerationCycle P-h Chart2.svg — Shoji Yamauchi — CC BY-SA 4.0
- RefrigerationCycle T-s Chart1.svg — Shoji Yamauchi — CC BY-SA 4.0
- Ejector for Refrigeration Cycle.svg — Shoji Yamauchi — CC BY-SA 4.0
- Air Source Heat Pumps Diagram.jpg — Alexxyz1 — CC0
- Reciprocating Compressor from an Industrial Refrigeration System.jpg — Endora6398 — CC BY-SA 4.0
- Expansion turbine+compressor refrigeration system.png — Mbeychok — Public domain
- RefrigerationCycle P-h Chart1.svg — Shoji Yamauchi — CC BY-SA 4.0
- P-T Diagram of the Pseudo-isobaric temperature gliding binary heat pump.png — Johan Enslin — CC BY 4.0
- Temperature-entropy chart of a basic Rankine cycle.svg — Olivier Cleynen — CC0
- Ozone-Oxygen-Cycle.svg — Philmo1 / Vectorization: Mrmw — CC0
- Water Cooled Chiller Diagram.png — Kevin Jay North — CC BY-SA 4.0
- Counterflow Heat Exchanger block diagram.png — William A. Kelley — CC BY-SA 4.0
- Scroll compressor.jpg — Yanior — Public domain
- Air conditioning unit-en.svg — Pbroks13 — CC BY 3.0
- Ozone hole extension 2023 ESA25113351.png — European Space Agency — Attribution
- Ozone Hole Continues Healing in 2024 (153523).jpg — NASA Earth Observatory image by Lauren Dauphin, using data courtesy of NASA Ozone Watch and GEOS-5 data from the Global — Public domain
- Chlorofluorocarbons (space-filling representation).jpg — see source page for author — Public domain
- HCFC22 concentration.jpg — NOAA — Public domain
- Liquid R-22.png — North747 — CC BY-SA 4.0
- ERV on the Psychrometric chart.jpg — MoeSalem — CC BY-SA 4.0
- Psychrometric chart - PMV method.png — Center for the Built Environment, University of California Berkeley — CC BY-SA 3.0
- GeothermalHeatPump.JPG — Gundeep Dorka — Public domain
- Geothermal heat pump.JPG — Dr Tzeferis Petros — CC BY-SA 4.0
- Figure 2 Psychrometrics of Cromer Cycle.jpg — DrSmith321 — CC BY-SA 4.0
- Largest ever Ozone hole sept2000.jpg — NASA — Public domain
- Scroll compressor.png — Casito — CC BY-SA 3.0
- HP compressor schematic.png — Peter Southwood — CC BY-SA 4.0
- Direct evaporative cooling.png — Soazig Kaam — CC BY-SA 3.0
- Heat pump system.jpg — KVDP (talk) — Public domain
- Visualization schemes for typical solar heat pump systems.jpg — Matteo.dantoni — CC BY-SA 3.0
- Air-Cooled Chiller System Diagram.jpg — Ridvan Ozbay — CC0
- Adaptive chart - adaptive method.png — Center for the Built Environment, University of California Berkeley — CC BY-SA 3.0
- Temperature-relative humidity chart - PMV method.png — Center for the Built Environment, University of California Berkeley — CC BY-SA 3.0
- Satellite Image of Ozone Hole in 2007.jpg — National Oceanic & Atmospheric Administration (NOAA) — Public domain
- Absorption heat pump configuration (refrigeration).jpg — Fuliyehuanshi — CC BY-SA 4.0
- Main components of a centrifugal compressor in isometric view.svg — Dr. Martin Heinrich — CC BY-SA 4.0
- Shell and Tube Heat Exchanger of Chiller.jpg — Saud — CC BY-SA 4.0
- Control circuit in household HVAC unit.jpg — Idahoprogrammer — CC BY-SA 4.0
- Cool under pressure- 386th ECES HVAC technicians in action (9047740).jpg — U.S. Air Force photo by Senior Airman Mark Colmenares — Public domain
- AC motor reverse without auxilary contacts - easy automatics for everyone.JPG — Dmitry G — CC BY-SA 3.0
- Atmospheric-Ozone.png — see source page for author — Public domain
- Ozone solar UV absorb DNA action.jpg — see source page for author — Public domain
- Cascade refrigeration (two-cycle) process schematic diagram.png — David M. Berchowitz and Yongrak Kwon — CC BY-SA 3.0
- Refillable refrigerant cylinder with a shadow.png — Лобачев Владимир — CC BY-SA 4.0
- Plate heat exchanger.svg — Snipre — Public domain
- Plate heat exchanger LS.JPG — Armchoir at Croatian Wikipedia — Public domain
- Crossflow Cooling tower.jpg — Ilanbar6 — CC BY-SA 4.0
- Carrier Outdoor Split Air Conditioner Heat Pump System (55005181522).jpg — Tony Webster — CC BY 4.0
- Simple electrical schematic with Ohms law.png — Danield101 — Public domain
- Ohm's Law with Voltage source.svg — inductiveload — Public domain
- Variable-frequency Drive System.png — Original uploader was C J Cowie at en.wikipedia — CC BY-SA 3.0
- PWM VFD Diagram.png — C J Cowie at English Wikipedia — CC BY-SA 3.0
- Can of DuPont R-134a refrigerant.jpg — No machine-readable author provided. Stephanie~commonswiki assumed (based on copyright claims). — CC BY-SA 3.0
- Autocascade refrigeration system.svg — MasterTriangle12 — CC BY-SA 4.0
- Absorption heat pumps type 1.jpg — Fuliyehuanshi — CC BY-SA 4.0
- Ts transcritical heat pumps.png — Ettore morosini — CC BY-SA 4.0
- HVAC system diagram.jpg — sammsheatingandair — CC BY-SA 2.0
- Radiant-based-HVAC-system-for-heating-and-cooling.png — RBean (talk) — CC BY-SA 3.0
- Lamneck-central-heating-gas-furnace-cutaway-diagram.png — American Gas Institute — Public domain
- Condensing Forced Air Gas Furnace.jpg — Wtshymanski — CC BY-SA 4.0
- ModCon boiler system.jpg — [Audetat] — CC BY-SA 3.0
- Effect of the Montreal Protocol.svg — Image provided by NOAA Chemical Sciences Laboratory, Boulder, Colorado, USA (https://csl.noaa.gov/) — Public domain
- Tube & fins heat exchanger tubestack.jpg — C.moreaux — CC BY-SA 4.0
- Finned-tube heat exchanger with axial fan.svg — GaunerBerlin — CC BY-SA 4.0
- Air Conditioner for a single room.jpg — Doggo19292 — Copyrighted free use-link
- Consumption of Ozone-Depleting Substances, OWID.svg — Our World In Data — CC BY 3.0
- Global warming potential of greenhouse gases over 100-year timescale (GWP₁₀₀), OWID.svg — Our World In Data — CC BY 3.0
- Flat-plate solar thermal collector, viewed from roof-level.png — SolarCoordinates — CC BY-SA 3.0
- Comparison of heat transfer coefficients.jpg — Ankit171032 — CC BY-SA 3.0
- Power Factor Correction Devices (5941059002).jpg — National Institute of Standards and Technology — Public domain
- Geothermal Binary System.svg — Wendell A. Duffield, John H. Sass — Public domain
- Tanks with ammonia or glycol chilling jackets.jpg — Agne27 — CC BY-SA 3.0
- Indoor Air Pollutants.jpg — Sophia.Rother — CC BY-SA 4.0
- Future ozone layer concentrations.jpg — NASA — Public domain
- Ozone hole recovery.jpg — NASA — Public domain
- Carnot heat engine 2.svg — Eric Gaba (Sting - fr:Sting) — Public domain
- Carnot Efficiency.svg — Krishnavedala — CC BY-SA 3.0
- Wet and Dry Bulb Thermometer.jpg — University of Dundee Museum Services — CC BY-SA 4.0
- New heat pump water heater that works much like a window air conditioner.jpg — ENERGY.GOV — Public domain
- SCADA system at a central chilled water plant.jpg — Rsparks3 — CC0
- Air handling unit.JPG — P199 — Public domain
- Comparing circuit breaker and fuse disconnector, the same current.JPG — Dmitry G — CC BY-SA 3.0
- Mitsubishi Heat Pump interior air handler.agr.jpg — ArnoldReinhold — CC BY-SA 4.0
- Air Conditioners.jpg — Eliomak Consults & Engineering Ltd — CC BY-SA 4.0
- ElectricalPanel.jpg — No machine-readable author provided. Tawker assumed (based on copyright claims). — Public domain
- Thermostat.jpg — FearChild — Public domain
- OfficeThermostat.jpg — The original uploader was Dante Alighieri at English Wikipedia. — CC BY-SA 3.0
- Refrigeration.png — Original uploader was Keenan Pepper at en.wikipedia — CC BY-SA 3.0
- Copper pipes with and without fibreglass insulation asj.jpg — Achim Hering — CC BY 3.0
- HCFC-22 mm.png — Jens Mühle — CC BY-SA 4.0
- Solid Desiccant cooling air system.png — IanVG — CC0
- Straight-tube heat exchanger 1-pass.svg — Sandstorm de — CC BY-SA 4.0
- Cool under pressure- 386th ECES HVAC technicians in action (9047739).jpg — U.S. Air Force photo by Senior Airman Mark Colmenares — Public domain
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