What is the maximum allowable relative humidity of the work area when placing TFIFRM?

• A. 60%
• B. 75%
• C. 85%
• D. 50%

Answer: (B)

Controlling humidity during the placement of TFIFRM is essential because the material’s cure and bond rely on a balanced moisture environment. If the air is too humid, moisture can become trapped in the setting mixture, slowing drying, creating surface defects, and weakening adhesion. That can compromise the performance and fire-resistance rating of the finished coating. A relative humidity of 75% is used as the practical limit to keep curing conditions reliable while still allowing work to proceed in typical field conditions. If humidity rises above this level, defer placement or implement dehumidification and ventilation to bring conditions back into range. The other humidity levels would either be unnecessarily restrictive or fail to protect the curing process.