Yes, I was wrong about unimflammable. That will teach to not look things up before I post!
lists nonimflammable as a non-hyphenated word. (And howzabout that hyphenate!
Webster's also has noninflammable--no hyphen. The prefix non is almost always linked to the rest of the word without a hyphen.
I was checking the Oxford dictionary online, wondering if I'd gotten my hyphen wrong. (Not according to them.) Got a real chuckle when I noticed that the website has two versions. You can click the Stars & Stripes for the US or the Union Jack for "UK and the rest of the world
." Once again, two peoples divided by a common language.