Timbercoat Insulating BasecoatClass B s1 dO + Class O fire protection paint for wood. Class B s1 dO + Class O fire protection paint for wood. Product Description: Thermoguard Anti Microbial Insulating Basecoat is the intumescent first part for the Thermoguard Anti Microbial SFR System that gives both anti viral fire protection and promotes better infection control on bare and painted wood. Advantages: For decorative interior and exterior timber Upgrade potentially dangerous wood