We empirically know that unpleasant smells are masked by pleasant fragrances. In 2009, we have reported that certain types of odorants suppress the transduction current in olfactory receptor cells (ORCs)(1). Since there was a big correlation between the channel suppression and human masking test (R=0.81), it is likely that the channel suppression by odorants is tightly linked with olfactory masking. In 2013, it was found that 2,4,6-trichloroanisole (TCA) which is the group of haloanisole(2) served anomalously strong channels suppression. TCA has been known for the cause of degradation of the quality of foods/beverages. Especially, in many vineyards, existence of TCA at pM (ppt) concentration causes big financially problem. In this study, we investigate the mechanism of channel suppression by haloanisoles and analogues. We monitored the current response using whole-cell recording from the isolated newt (Cynops pyrrhogaster) ORCs. The experiments were performed under the latest ethical guidelines for animal experimentation at Osaka University, based on international experimental animal regulations. After caged cAMP was introduced to ORCs beforehand, UV light stimulation was applied to the cilia exclusively. First, we obtained pure transduction channel current by caged photolysis. Second, chemicals were applied to ORCs during the same UV stimulation. From the current suppression, we obtained the efficiency of the substances as suppression ratio (SR). In this study, EC50 of TCA was identified to be 0.19 μM (in a puffer pipette). Other natural suppressor geraniol and artificial CNG channel blocker L-cis diltiazem were also tested, EC50s were 5.8 μM and 29 μM, respectively. It was surprising to see that the least effective concentration of TCA was 1 aM with the U-tube system (SR=0.12±0.02, n=3)(Mean±S.D.). Furthermore, to elucidate the mechanism of strong channel suppression, we focused on the high LogD of TCA (3.87) and high channel density in the cilia (1750 channels/μm2)(3). Extremely high efficiency of TCA may be based on high surface to volume ratio of the cilia and dissolution into the ciliary membrane. We examined the SR of TCA that we changed the membrane lipid components. SRs of TCA were decreased by cholesterol incubation for 2h (SR=0). LogD is an index for the hydrophobicity, therefore haloanisole and analogues may dissolve into lipid bilayer. Then, channel suppression could be caused by conformation change by remaining haloanisoles in the ciliary membrane. These results may suggest that CNG channels are suppressed through a partitioning of those substances into the lipid bilayer. The findings not only reveal a mechanism of flavor loss of foods/beverages, but also suggest certain molecular structures as possible olfactory masking agents and powerful channel blockers.