Which signs indicate a possible leak in a propane system?

The presence of oily residue, a hissing sound, or the distinctive smell of propane strongly indicates a potential leak in a propane system. Propane is odorless in its natural state, but a compound called ethyl mercaptan is added to give it a characteristic odor similar to rotten eggs, making it detectable even in low concentrations.

If you observe any oily residue near the fittings, it could suggest that propane is leaking and condensing, leaving this oily film behind. A hissing sound may indicate gas escaping from a fitting or valve under pressure, while the smell of propane is a critical warning sign that immediate action is required. This combination of signs provides clear evidence that there is a malfunction within the system, warranting further investigation and potential repair to ensure safety.

In contrast, other options might suggest maintenance or inspection needs but are not indicative of a leak. For example, bright colors on fittings don’t necessarily mean there's a problem, and cold temperatures around fittings might arise from normal operation rather than a leak. Rust can indicate age or corrosion, but it doesn't directly signify a leak on its own without accompanying evidence like those mentioned.