And to get technical, "non-inflammable" is a double negative, so we're back to needles that readily catch on fire here! Shoulda been just inflammable if they wanted something fire resistant.
Maybe....maybe not. Inflammable actually means the same as inflammable. There's an interesting Usage note
if you scroll down this page
. Typically this would be a double negative but in this case I don't think it is; proper usage is another matter entirely. If you notice that this vintage pattern is dated 1958, the use of the term is not surprising. Anything to draw attention to a product is fair game in advertising.
starbuck, I looked at the shorts pattern, missed your post earlier, and who knows? I might decide to try it.