Semtex

"Have you worked much with munitions, agent Fitz? Explosives are a fascinating specialty, very exacting."

- John Garrett

Semtex is a plastic explosive used in commercial blasting, demolition and in certain military applications.

History
After Coulson's Team infiltrated a secret compound known as The Guest House, aided by agent John Garrett, they found a timer connected to a vast amount of Semtex scattered all over the bunker, and enough to bring down the mountain on top of the complex.

While agents Phil Coulson and Leo Fitz were looking for the drugs needed to save Skye's life, agents Garrett and Grant Ward unsuccesfully searched for the detonator or a way to deactivate the explosives, so they used some of the explosive to blow the bulletproof glass doors that were closed upon their entrance.

When the timer went to zero, the Semtex explode burying The Guest House under 100 feet of rock, and agents Coulson and Garrett, the last ones in exiting the complex, got to board on The Bus just in time to avoid the effects explosion