What is not allowed when performing thickness testing on TFIFRM?

The response indicating that "all of the above" is not allowed when performing thickness testing on TFIFRM (Thermal Fireproofing Insulating Finish Repair Material) effectively highlights that none of the mentioned methods—visual inspection, prior testing, or surface scraping—are suitable for thickness testing in this context.

Visual inspection is not a reliable method for assessing the thickness of fireproofing material, as it does not provide accurate measurements and can lead to misinterpretations regarding compliance with fire safety standards. Prior testing may not reflect the current condition or application of the fireproofing material, as the properties can change over time or due to external factors. Surface scraping could damage the material, compromising its integrity and affecting its fire-resistance capabilities.

Thus, adhering to proper testing methods is crucial to ensure that the fireproofing material meets safety regulations and performs as intended. Using accurate and approved techniques ensures that thickness measurements are reliable, ultimately providing the necessary level of protection in fire scenarios.