Steve, it doesn't mean they spontaniously combust! LOL The ones marked not intended for childwear, have not been treated with a nonflamable. Neither have cottons for that matter. Law requires the flannels to state the not intended warning if it is not pretreated. 100% cotton flannel is no more ignitable than regular cotton. If you use flannel for batting as in a summer or baby quilt, I would suggest washing it a few times first. The amount of shrinkage is significant and unpredicatable.