Pyro-Guard treatment, like all other interior type fire-retardant treatments, contains chemicals that are somewhat water soluble and this is why it can only be used in dry interior applications.
Pyro-Guard treatment also provides resistance to decay and termites but it cannot be used in ground contact, damp or wet conditions, or other applications that require the use of preservative treated wood.
The preservative qualities of Pyro-Guard and other brands of FRTW are a coincidental by-product of treatment and do not override the fact that it must stay dry in use.
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.
Pyro-Guard fire-retardant treated wood can be used in contact with concrete or masonry that will not get damp or wet in service. For example, window blocking, furring strips or cap blocking on concrete or masonry exterior walls are acceptable applications as long as they are enclosed within the weather envelope and not exposed to dampness or wetting.
The treatment is permanent for the life of the structure as long as the wood is used in dry conditions.
Pyro-Guard can be used in contact with dry concrete floors. If in doubt about potential dampness, 30-pound felt can be used as a moisture barrier between Pyro-Guard and concrete or masonry.
Pyro-Guard treated wood should not be used on concrete floors that are subject to dampness, wetting, washing down, or flooding. Codes require base plates on concrete floors in contact with the earth to be preservative treated.