BATHROOM EXTRACTOR FAN NOT EXTRACTING?

A QUALIFIED ELECTRICIAN HAS FITTED A CEILING FAN IN OUR NEW SHOWER-ROOM(6'X7') IT IS PASSING THE SUCTION TEST ie.HOLDING A PIECE OF TOILET TISSUE VERY FIRMLY IN PLACE BUT IS NOT IN ANY WAY REMOVING STEAM. IT IS AN IPX7 RATED FAN (THE SECOND ONE AS THE FIRST ONE WAS SLIGHTLY LESS POWERFUL)
THE FAN IS DUCTED INTO THE ROOFSPACE AND THROUGH A NEARBY EXTERIOR WALL. OUR ELECTRICIAN HAS FITTED MANY OTHER FANS OF THIS TYPE BUT HAS NOT COME ACROSS THIS PROBLEM BEFORE. CAN ANYONE HELP PLEASE?

JOYCE
March 2008