Pyro-Guard treatment, like all other interior type fire-retardant treatments can only be used in dry interior applications.
Keep stored Pyro-Guard material dry by covering the bundle, storing under shelter, elevating to prevent ground contact, and providing for air circulation around the wood. Upon installation, it should be covered and protected from rainfall as soon as possible. Roof sheathing should be promptly covered with felt for temporary protection until the roofing is applied.
Limited exposure while unprotected during construction can be tolerated, but if rained on the wood should be allowed to dry before enclosure. The treatment is permanent for the life of the structure as long as the wood is used in dry conditions.