A fellow member of a car forum that I frequent posted recently that he had to deal with this. He was ready to board a plane in Ohio and was checked positive for gun powder residue on his hands. He was pulled aside by TSA and asked to explain why. After he did, he was "allowed" to get on his flight.
Four days prior, he and his son did some bird hunting with shot guns. He was shocked that numerous hand washings and four showers in the preceding days had not removed all traces of powder.
Give it enough time, and I predict that every powder will be required to have a chemical signature that will I.D. the source. When that happens, they can see if your answer matches the one the scanner gives.
Then I will feel so much safer.