HVAC Exam Lab
Core and Type III

Safety, cylinders and handling

The practical half of the exam.

Why this one catches people

Spread across 18 different topics rather than concentrated, so it is easy to revise everything else and still walk in short on this. It is also the material most likely to matter on a real job.

26 questions in our bank map to this material, across 16 outline topics and 3 exam sections (Core (Group I): 14, Type II: High-Pressure Systems: 3, Type III: Low-Pressure Systems: 9).

Why this is easy to under-revise

The safety material is not one topic. It is spread across 16 separate outline references, which means no single revision session feels like it covers it. It is also the part of the syllabus most likely to matter on a real job.

The recurring themes

  • Refrigerant displaces oxygen. It is heavier than air, so it collects at floor level in a confined space. Asphyxiation is the mechanism, not toxicity.
  • Cylinders have fill limits. Liquid expands as it warms, and a cylinder filled solid has nowhere for that expansion to go.
  • Never pressurise with oxygen or compressed air. Use nitrogen. Oxygen plus oil is an explosion; compressed air introduces moisture.
  • Heat decomposes refrigerant into far more dangerous products, which is why you do not braze on a charged system.

Where people go wrong

  • Overfilling recovery cylinders. Refrigerant expands, and the fill limit exists for that reason.
  • Forgetting that refrigerant vapour displaces oxygen and pools low in a confined space.
  • Using oxygen or compressed air to pressurise a system for leak detection.
  • Assuming a deep vacuum is harmless to run a compressor in. On low-pressure machines it is not.

Drill exactly this

26 questions in the bank cover this material. Anything you miss goes to your notebook so you can come back to it.

Quick practice drill

15 questions · 18 minutes · pass at 70%

Questions are sampled to mirror the official domain weighting. The timer starts when you begin; you can flag questions and return to them before submitting.

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