The great canvas smell is DDT and not really healthy!
If you know a canvas maker arround (in German called Sattler), get the canvas made from new non vinyl stuff. These guys usually know where to get it, it's their profession. Else you have to live with 40 or more years old stuff. If unpropperly handeled, it is as bad as the stuff you probably own allready.
For the old stuff ventilation has the main pryority! if not vented, forget it!
Wolf from Germany