for rooms expected to have high humidity, primarily kitchens, bathrooms, and laundry rooms. Other damage Foam insulation and the gypsum part of sheetrock are easily chewed out by honeybees when they are setting up a stray nest in a building, and they want to enlarge their nest area. High-sulfur drywall illness and corrosion issues A substantial amount of defective drywall was imported into the United States from China and incorporated into tens of thousands of homes during rebuilding in 2006 and 2007 following Hurricane Katrina and in other places. Complaints included the structure's foul odour, health effects, and metal corrosion. The emission of sulfurous gases causes this. The same drywall was sold in Asia without problems resulting, but US homes are built much more tightly than homes in China, with less ventilation. Volatile sulfur compounds, including hydrogen sulfide, have been detected as emissions from the imported drywall and may be linked to health problems. These compounds are emitted from many different types of drywall. Several lawsuits are underway in many jurisdictions, but many of the sheets of drywall are simply marked "Made in China", thus making the manufacturer's identification difficult. An investigation by the Consumer Product Safety Commission, CPSC, was underway in 2009. In November 2009, the CPSC reported a "strong association" between Chinese drywall and corrosion of pipes and wires reported by thousands of homeowners in the United States. The issue was resolved in 2011, and now all drywall must be tested for volatile sulfur, and any containing more than ten ppm is unable to be sold in the US. Fire resistance Some fire barrier walls are constructed of Type X drywall as a passive fire protection item. Gypsum contains the water of crystallization bound in the form of hydrates. When exposed to heat or fire, this water is vaporized, which retards heat transfer until the water in the gypsum is gone. The fire-resistance rating of the fire barrier assembly is increased with additional layers of drywall, up to four hours for walls and three hours for floor/ceiling assemblies. Fire-rated assemblies constructed of drywall are documented in design or certification listing catalogues, including DIN 4102 Part 4 and the Canadian Building Code, Underwriters Laboratories and Underwriters Laboratories of Canada (ULC). Tests result in code-recognized designs with assigned fire-resistance ratings. The resulting designs become part of the code and are not limited to use by any manufacturer. However, individual manufacturers