What bonding agent is allowed on substrates beneath SFRM?

The correct choice indicates that a bonding agent is allowed on substrates beneath Spray-Applied Fire-Resistive Material (SFRM). This is significant because bonding agents play a crucial role in ensuring the adhesion of fireproofing materials to the substrate, which is essential for the effectiveness and integrity of the fire-resistive system.

Using an appropriate bonding agent can enhance the bond between the substrate and the SFRM, contributing to its overall performance during fire conditions. It is critical that the bonding agent used conforms to industry standards and compatibility requirements, as this will affect both the application process and the long-term performance of the fireproofing system.

In this context, while the other choices could imply materials that may not specifically serve the same purpose of adhesion or might not comply with the codes and best practices in fireproofing applications, the bonding agent is explicitly recognized for its utility in ensuring that SFRM adheres properly, thereby maintaining the protective properties required for fire safety.