CNG Study Guide 2026
Everything you need to pass the CNG exam in one place: the exam format, every topic to study, real practice questions with explanations, flashcards, and full-length practice tests. Free, no sign-up needed.
📋 CNG Exam Format at a Glance
📚 CNG Topics to Study (69)
✍️ Sample CNG Questions & Answers
1. What type of portable fire extinguisher is most appropriate for use at a CNG fueling station?
ABC dry chemical extinguishers are appropriate at CNG stations because they handle ordinary combustibles, flammable gases/liquids, and energized electrical equipment.
2. What material are piston rings and seals in oil-free CNG compressors commonly made from?
PTFE and carbon-filled composite seals are used in oil-free CNG compressors because they are chemically resistant, maintain integrity at high pressures, and require no lubrication.
3. During a post-maintenance pressure test, a technician pressurizes the system and leaves it for 10 minutes. Pressure drops 20 psi. What does this indicate?
Any pressure drop during a static pressure hold test indicates a leak; the system must not be returned to service until the leak is located and corrected.
4. When using a manometer to check CNG low-pressure regulator output, the reading fluctuates widely with engine speed changes. This indicates:
A healthy regulator maintains steady output pressure across engine speed ranges; wide fluctuations indicate a diaphragm or spring failure inside the regulator.
5. A Type 4 CNG cylinder is constructed from:
Type 4 cylinders use a high-density polyethylene (HDPE) or nylon plastic liner that is completely overwrapped with carbon fiber composite for maximum strength at minimum weight.
6. What is the primary chemical component of compressed natural gas?
Natural gas is composed primarily of methane (CH4), typically 90% or more by volume, with small amounts of ethane, propane, and other gases.
🎯 Free CNG Practice Tests
📖 CNG Guides & Articles
- CNG Injector: How It Works, Types, Maintenance, and What Fleet Operators Need to Know
- Swift CNG: Everything You Need to Know About Compressed Natural Gas for US Fleets and Drivers
- Mobile CNG Stations: How Compressed Natural Gas Fueling Works on the Go
- Home CNG Compressor for Sale: What US Buyers Need to Know Before Investing
- CNG Map: How to Find CNG Stations Across the USA
- Permanent CNG Compression Hubs: How They Work, What They Cost, and Why Fleets Rely on Them
- CNG Fleet: The Complete Guide to Compressed Natural Gas Fleet Management
- CNG Certification Test: Complete Study Guide and Prep Hub for 2026