As the first relay between peripheral and central olfactory systems, the human olfactory bulb (OB) plays a dynamic role in odor perception. This study investigated OB time-frequency responses to odors of different valences under active versus passive sampling. Thirty-two participants underwent either inhalation-synchronized (active) or respiration-independent (passive) odor stimulation while electrobulbogram signals were recorded. Across both sampling modes, OB activity followed a consistent sequence of early gamma, scattered beta bursts, and late gamma-beta oscillations. Active sampling induced stronger and more widespread gamma activity throughout processing. Participants were further grouped based on N1-P2 ERP amplitudes. ERP-sensitive individuals exhibited enhanced early low-beta OB activity, whereas ERP-insensitive individuals showed stronger mid-to-late gamma and beta responses, suggesting compensatory stimulus re-evaluation. These findings indicated that OB gamma and beta oscillations encoded odor valence while reflecting temporal processing differences shaped by sampling strategy and individual sensitivity, highlighting the flexibility of early-stage human olfactory processing.