An environmental engineer uses two independent sensors—a ground-based electrochemical sensor (Sensor A) and an aerial IR camera (Sensor B)—to detect ammonia leaks. They define three hypotheses: H1 (No leak), H2 (Minor leak), and H3 (Major leak). Given prior probabilities and likelihoods from lab data, they compute the posterior probabilities assuming sensor independence. Sensor A reports a moderate concentration (E1), and Sensor B detects a small plume (E2), leading them to classify the event as a likely major leak (H3). Emergency responders, however, find only a minor leak caused by a faulty valve. It is later revealed that warm airflow influenced both sensors’ readings. What was the mistake in the engineer’s analysis, and how should it be corrected?