TALLAHASSEE – The clock is ticking for Florida homeowners who want to be part of a class-action lawsuit against a manufacturer believed to be a source of defective Chinese drywall.

Attorney General Bill McCollum says homeowners must sign up by Dec. 2 to participate in the lawsuit against Knauf Plasterboard Tianjin Co.

Homeowners must show proof, including a photo clearly labeling the defective product. The private, class-action case is scheduled to be heard in federal court in Louisiana on Jan. 25.

Defective Chinese drywall emits a sulfuric smell, has been linked to health problems and can cause corrosion to copper and other metals.

It is estimated that about 100,000 homes nationally contain Chinese drywall. Officials believe about 35,000 homes in Florida are affected. They cite new building during the housing boom and after heavy hurricane seasons of 2005 and 2007 for the high number of cases here.

The U.S. Consumer Product Safety Commission reports about 1,300 complaints from Florida homeowners for Chinese drywall. The Florida Department of Health reports 673 complaints.