The purpose of these tests is to determine whether the material can propagate a detonation (zero-gap test) and if the test material will transition from a deflagration to an explosion under high confinement (internal ignition test). If the material has either of these explosive characteristics, it should be classified as an explosive in a manufacturing operation. If the material is shown not to have these explosive characteristics then the material may be classified as something other than an explosive, even though it may be sensitive to certain stimuli or still exhibit explosive reactions under extreme or rare circumstances. Substances, which are both explosive and easily initiated, should be considered a 1.1 for manufacturing applications.

Zero Gap Test

The test determines if a material will propagate a detonation when subjected to an adjacent detonation. The sample is loaded into a pipe facing a steel witness plate. A detonator is used to initiate a pentolite booster (50% PETN/50% TNT), which provides a known shock to the sample. The criteria for a "go" reaction are that the pipe is fragmented along its full length and/or a hole is punctured through the witness plate. The test is conducted two or three times unless detonation occurs. The UN gap test and the NOL card gap test can both be used for the same purpose when conducted at the zero-gap level.

Internal Ignition (20-Gram Bag)

The test determines if a material will explode or detonate when ignited under confinement. The sample is loaded into a pipe with 3000 pound pressure tested forged steel end caps. A 20-gram black powder bag igniter is inserted into the center of the pipe, the pipe is filled with test material and the ends capped. After the igniter is fired, if either the pipe or at least one of the end caps is fragmented into two or more distinct pieces then the test result is positive. The test is considered negative (the material passes) if the pipe is merely split open or the caps are sheared off in one piece. Three trials are performed unless a transition from deflagration to explosion occurs earlier.