Greetings. A year or two ago we decided to replace the ceramic tile in our living room with carpet. After removing that tile, we found the original tile underneath. It was a black and white checkerboard tile put in when the house was new (1923 or so). It was ruined obviously so it needed to be removed. Knowing asbestos was not used in tiles until the 1940s I just tore it out. Underneath that old tile was a layer of greyish felt. It was stuck down to the floor (and the tiles were stuck on top of it).

Now a year or so later I learned even some old tiles sometimes used asbestos in their "backing". Though this seems less like tile backing and more like an actual separate layer glued to the floor, then the tile applied on top (though its very old so I can't be positive).

We didn't fully remove this felt layer, just laid carpet pad and carpet over top.

My questions are, could that old felt layer contain asbestos, and should I now go back and pull up the carpet/pad to remove it? Or is it pretty well sealed down by pad/carpet? It was definitely "ripped up" in the tile removal process. Would walking/vaccuming the carpet agitate and release fiber down under the carpet and pad?

It could contain asbestos but is hard to determine as it is so old. You should get a piece of the felt and get it tested for Asbestos before pulling the carpet up and removing all of the felt. Check your local yellow pages for a company that can do this for you. Not sure walking / vaccuming will release any of the fibers but it would be worth the test to make sure before tearing it all up.

Well I guess my follow-up would be, is it LIKELY to be asbestos (felt backing on a 1920's tile/linoleum) or is there a good chance its not? I have scoured the net and there is very little on that particular topic (though plenty on all kinds of other asbestos issues). And yeah I guess my next course is a test. I appreciate any replies.

Really hard to say if it has asbestos in it. I'd guess it does not, but the flooring you removed may have. The test is definitely your next step.