The National Institute of Standards and Technology (NIST) concluded the accepted version was more than sufficient to explain the collapse of the buildings. NIST and many scientists refuse to debate conspiracy theorists because they feel it would give those theories unwarranted credibility. Specialists in structural mechanics and structural engineering accept the model of a fire-induced, gravity-driven collapse of the World Trade Center buildings without the use of explosives. As a result, NIST said that it did not perform any test for the residue of explosive compounds of any kind in the debris.