RadonSeal Plus Deep-Penetrating Concrete Sealer (2.5-gal) &ndash; Waterproofs, Strengthens, and Mitigates Concrete Permanently! MONEY BACK GUARANTEE ECO-FRIENDLY  Non-toxic, Nonflammable, ZERO VOCs. Safe for Use Indoors. PERMANENT  RadonSeal is Permanent! No Reapplication Needed. PENETRATES - Penetrates into Concrete, Seals Below the Surface. Restricts Moisture, Dampness, Water Vapor, and Radon Gas through Concrete