Leak detection for ammonia refrigerant When checking for leaks in an ammonia (NH3) refrigeration system using a burning sulphur stick, what visible indication confirms the presence of ammonia?

Introduction / Context:
Safe and quick leak detection is essential in refrigeration maintenance. Ammonia (NH3) systems are common in industrial refrigeration due to high latent heat and zero ODP, but they require distinct detection methods because NH3 has strong odour, high affinity for acids, and reacts with certain combustion products.

Given Data / Assumptions:

• Technician uses a burning sulphur stick near suspected joints.
• Airborne products include sulphur dioxide (SO2) and sulphur trioxide (SO3).
• Ammonia is a basic gas that forms salts with acidic oxides.

Concept / Approach:
When SO2/SO3 from the sulphur stick contacts ammonia, they react to form ammonium sulphite/sulphate aerosols. These salts appear as dense white fumes or “white smoke,” providing a clear visual indicator of NH3 presence. This simple field method supplements electronic detectors and soap solution tests.

Step-by-Step Solution:

Verification / Alternative check:
Soap bubble solutions can also identify leaks by visible bubbling. Electronic ammonia sensors provide quantitative detection and alarms, but the sulphur-stick method remains a classic qualitative check.

Why Other Options Are Wrong:

Blue flame or color changes are unrelated to NH3 detection with sulphur sticks.Green vapour trails or black droplets are not characteristic products of NH3–SOx interaction.Odour alone is not the recommended confirmation method due to safety and desensitization risks.

Common Pitfalls:
Holding an open flame too close to combustible materials, or using the method in confined, poorly ventilated spaces. Prefer non-ignition methods where flammability hazards exist, though NH3 itself has a relatively narrow flammability range.

Final Answer:

White smoke or fumes forming around the leak point