Service practice: Using a halide torch to detect a leak of Freon-type refrigerant (old CFC/HCFC), the flame colour typically changes to which hue?

Introduction / Context:
Before modern electronic leak detectors, technicians often used halide torches to identify CFC/HCFC leaks. Recognizing the characteristic flame colour change is part of historical service knowledge and safety lessons.

Given Data / Assumptions:

• Halogenated refrigerant (e.g., R-12, R-22) is present in the air near the torch intake.
• Combustion products interact with halogens, producing a coloured flame.
• The method is discussed for education; it is not recommended due to safety/environmental concerns.

Concept / Approach:
When halogen vapours are drawn into the halide torch flame, copper halides form and emit a greenish colour. This bright green or blue-green tint indicates the presence of a halogenated refrigerant in the surrounding air.

Step-by-Step Solution:

Verification / Alternative check:
Modern electronic detectors (heated diode, infrared) are safer and more sensitive. They confirm leaks without combustion by-products.

Why Other Options Are Wrong:

Yellow/red/orange/violet are not the characteristic halide indication for CFC/HCFC leaks.

Common Pitfalls:
Using open flames near refrigerant or oil can be hazardous; always follow contemporary codes and use approved electronic detectors.

Final Answer:

bright green