CLK silicone sealant has been introduced by Nelson Firestop, Tulsa, Oklahoma. Installed by a caulking gun, or by manually trowelling using a mason's trowel or putty knife, CLK sealant is ideal for firestop penetrations and construction joints, such as around metallic pipes or conduits, and for floor-to-wall, floor-to-floor and head of wall applications. CLK is waterproof, smoke-proof and gas-proof. This non-shrinking and non-toxic sealant maintains its flexibility and allows for movement or vibration, so it retains its sealing qualities even with expansion, contraction or other fluctuations. In addition to protecting and preventing the spread of fire, smoke, gases and water, CLK has been acoustically tested to demonstrate noise reduction properties. Nelson Firestop CLK meets UL1479, ASTM E-814, ASTM E-1966 and ASTM E-84 specifications.