Check around with a bunch of your local drycleaners... there is a process (totallllly slipping my mind at the moment) that some drycleaners have to process clothes and such that have been in a fire. It removes smoke smells and other nasty stuff.
Not all drycleaners have it obviously, as it takes a room that seals off and they use some sort of static charge or something. But there is at least one in every city usually. Might not work on your chair but its worth the time to call and find out.
Insurance companies LOVE this system. lol