Foster® 30-90™ Vapor-Safe® Mastic is non-flammable when wet and has a mild latex “paint type” odor. It is designed for heavy duty/industrial use on pipes, vessels, ducts, and equipment operating below ambient temperatures. It may also be used indoors.

Vapor-Safe Mastic has the water resistance and low water vapor permeance normally found only in solvent-based products. It can be used in high humidity environments, and greatly retards water vapor permeation.

Vapor-Safe Mastic is ideal for vapor sealing ASJ, FRK, and FSK jackets and board facings at joints, laps and over staple and weld pin punctures. It is an excellent duct board closure sealant. Do not exceed 1/8" (3.2 mm) wet film thickness.