What is the maximum allowable relative humidity when drying SFRM for density testing?

The maximum allowable relative humidity when drying Spray-Applied Fire-Resistive Material (SFRM) for density testing is established to ensure accurate readings of moisture content, which can significantly affect density measurements. When the relative humidity is too high, it can hinder the evaporation of moisture from the sample, leading to inaccurate density results that do not reflect the true properties of the material.

Setting the threshold at 60% relative humidity provides a balance that minimizes the risk of moisture interference while still accounting for some environmental variability that might occur on a job site. This level is generally recognized in industry standards as being conducive to effective drying without compromising the integrity of the test results.

If the humidity were set higher, there would be a risk of moisture retention that could skew the density measurements, leading to potentially less reliable performance evaluations of the SFRM. Thus, maintaining a maximum relative humidity of 60% ensures both the efficacy of the drying process and the accuracy of density testing results.