Top 10 F-Gas Exam Topics You Must Know

Focus Your Study Time Where It Counts

The City & Guilds 2079 F-Gas certification exam covers a wide range of material, and trying to study everything with equal depth can be overwhelming. Based on the exam syllabus and common question patterns, these are the ten topics that appear most frequently and carry the most weight. Prioritise these areas in your revision to give yourself the best chance of passing.

1. The EU F-Gas Regulation 517/2014

This is arguably the single most important topic on the exam. Expect multiple questions on the HFC phase-down schedule, GWP limits for different equipment types, mandatory leak checking frequencies, record-keeping obligations, recovery requirements, and certification rules. You should know the key dates, thresholds (5, 50, and 500 tonnes CO2 equivalent), and which substances and activities are covered by the regulation. Do not underestimate how much of the exam is drawn directly from regulatory knowledge.

2. Refrigerant Properties and Identification

You need to know the common refrigerants by their R-number designations and understand their key properties. This includes R-410A, R-32, R-134a, R-404A, R-407C, R-290, R-744, and R-1234yf, among others. For each, you should know the approximate GWP value, whether it is an HFC, HFO, or natural refrigerant, its safety classification (flammability and toxicity under the A/B and 1/2L/2/3 system from EN 378), and whether it is a pure substance, zeotropic blend, or azeotropic blend. Understanding glide temperature for zeotropic blends is also frequently tested.

3. The Refrigeration Cycle

A solid understanding of the basic vapour compression refrigeration cycle is essential. You should be able to identify the four main components (compressor, condenser, expansion device, and evaporator) and explain what happens to the refrigerant at each stage in terms of pressure, temperature, and physical state. Know the difference between subcooling and superheating, why they are important, and where they occur in the cycle. Questions on pressure-enthalpy diagrams also appear, so be comfortable reading and interpreting them.

4. Leak Checking Methods and Requirements

Leak detection is a core competency tested heavily in the exam. You should understand both direct methods (electronic leak detectors, UV dye, bubble testing with nitrogen/OFN, and visual inspection) and indirect methods (monitoring system pressures, temperatures, superheat, subcooling, sight glass condition, and energy consumption). Know the mandatory leak check intervals based on CO2 equivalent charge, the requirement for follow-up checks after repairs, and when permanent leak detection systems must be installed (500 tonnes CO2 equivalent and above).

5. Recovery, Recycling, and Reclamation

Understand the legal obligation to recover F-gases before equipment disposal and during certain maintenance procedures. Know the difference between the three Rs: recovery (removing refrigerant from a system and storing it in a container), recycling (basic cleaning of recovered refrigerant, typically by filtering and drying, for reuse in the same type of equipment), and reclamation (processing recovered refrigerant to restore it to virgin specification, which can only be done at an approved facility). You should also understand the correct procedures for using recovery machines and the safety precautions involved.

6. Environmental Impact of F-Gases

The exam tests your understanding of why F-gases are regulated in the first place. Key concepts include the greenhouse effect, global warming potential (GWP — the measure of how much heat a gas traps relative to CO2 over 100 years), ozone depletion potential (ODP — note that HFCs have zero ODP but high GWP), and the difference between the ozone layer problem and climate change. Understand why the Montreal Protocol addressed CFCs and HCFCs, while the F-Gas Regulation and the Kigali Amendment target HFCs.

7. System Components and Their Functions

Beyond the four main cycle components, you should know the purpose and operation of key ancillary components: receivers, accumulators, filter-driers, sight glasses, oil separators, reversing valves (for heat pumps), solenoid valves, pressure relief devices, service valves, and Schrader valves. Questions often ask you to identify what a component does, where it is located in the system, or what symptom indicates it has failed.

8. Brazing and Pipework Procedures

Expect questions on safe brazing procedures for copper refrigerant pipework. Key points include the requirement to use an oxygen-free nitrogen (OFN) purge during brazing to prevent copper oxide scale forming inside the pipe, the correct gas pressures for purging, the types of brazing alloys used, and relevant safety precautions (fire risk, ventilation, hot work permits). You should also understand pressure testing procedures using OFN and the importance of evacuating the system with a vacuum pump before charging.

9. Charging and Commissioning

Know the correct procedures for charging a system with refrigerant. This includes understanding the difference between liquid charging and vapour charging, when each method is appropriate, and the risks of incorrect charging (such as liquid slugging the compressor). You should know how to weigh in a precise charge using scales, how to use superheat and subcooling measurements to verify correct charge levels, and the importance of checking the manufacturer’s data plate for the specified charge quantity.

10. Health and Safety

The exam includes questions on the health and safety hazards associated with F-gas work. Key areas include the risks of oxygen displacement in confined spaces (F-gases are heavier than air and can accumulate at low levels), frostbite from contact with liquid refrigerant, high-pressure hazards from pressurised systems and cylinders, the importance of PPE (safety glasses, gloves, and protective clothing), and the correct procedures for handling and storing refrigerant cylinders (upright, secured, away from heat sources, within date for inspection).

How to Use This List

These ten topics form the backbone of the F-Gas certification exam. While you should still review the full syllabus, dedicating the majority of your study time to mastering these areas will significantly improve your chances of success. For each topic, aim to understand the underlying principles rather than simply memorising facts — the exam questions are designed to test comprehension, not just recall.

Combine your study of these topics with regular practice questions, and you will be well prepared to achieve a strong pass on exam day.