prohibited items
 

Maybe somebody out there can help me with this one. I was boarding a flight from Korea the other day and was stopped at the gate and told I couldn't board since the Airline had discovered a prohibited item in my check-in bag. They told me it was an aersol can of boot waterproofing spray, which I had carried on other occasions, not realising it was prohibited, but it would be removed on this occasion. They asked for the lock combination, and I was allowed to board. Sure enough the can was removed and the bag closed. Questions - How did they know precisely what was in the can? Can X-Ray machines read labelling? There was another aerosol can of deodorant also in the bag - this was not removed, though it does say on the can that it's also inflammable. Just interested.

Thanks.