Re: conc labels I think both the 5th and 6th character carry concentration info. Based on the paper, I think: - the 5th character = conc of TCE in the odorant - the 6th character = conc of odorant in air So, for class-0 (TCE-absent), it makes sense that the 5th character would be all zero, since there's no TCE. In class-1, the 5th character takes values in (0,1,2,7,A), and the 6th character takes values in (2,7). Based on the info in the paper, the low conc data corresponds to '02' from class-0, and 'A2' from class-1.