ASTM E-84 is a comparative test, and as such, there is no real 'pass' or 'fail'. The test generates numbers expressed as Flame Spread Index (FSI) and Smoke Developed Index (SDI), and while there are no pass-fail criteria in the standard, certain codes and regulations define required FSI value and/or SDI value for applications and installations. If a sample’s values do not meet code directives, the product may be limited or prohibited. In such cases, it may be advisable to run additional tests (perhaps with modified materials) to legitimately improve the product’s FSI or SDI.