Embodiments of a system that can detect leaks that occur in seals, and in one example, to seals found in a valve. In one embodiment, the system utilizes sensors that measure fluid properties of a sample volume proximate to the seal. The system can compare data from these measurements with data from a sample of a reference fluid (e.g., ambient air) to indicate the presence of working fluid in the sample volume. This result may indicate problems with the seal, e.g., degradation of the seal that is meant to prohibit the working fluid from migrating out of the valve.