In this paper damage mechanics approach is used to investigate the effect of crash and damage caused by impact in steel cylinder filled by Compressed Natural Gas (CNG). The Canadian Standard Association (CSA) for CNG cylinders is used as a damage detection criterion and cylinders ability to reuse. Johnson-Cook damage model is used to compute the cylinder failures. Simulations are carried out in different impact directions, and the effect of cylinder internal pressure, collision velocity and the fall height are analyzed. Also failures due to collision for various situations are studied and discussed. Investigations for cases including crash and drop tests showed that the maximum damage in cylinder is created for the case of normal impact and by changing the impact direction from normal to side, the amount of damage will be decreased. Also by eliminating failed elements and comparing the damage depth caused by collision using the CSA standard, it was observed that in the most cases of normal accident and drop tests, cylinders have been damaged and lose its ability to use. However, in side impact cases cylinder is intact or can be reused after repairing.