Asbestos is generally only dangerous to those who worked with it every day. To get sick from asbestos you need to breath it in in a powdered form on a regular basis. Even if there is any in a postwar smoke unit, to pose a danger it would have to be pulverized and then spread into the air. This does not happen in ordinary operation. And it would be too small of an amount to cause lung damage anyway. So, nothing to worry about.
-Nathan
