A substrate is the supporting material onto which a washcoat and catalyst formulation are applied in a catalytic converter. Four different commercially available diesel exhaust purifiers were tested for durability and resistance to vibration. Each purifier contained a flow-through monolith substrate of different. design as well as the necessary packaging elements. A hot vibration test was used to evaluate each sample. This is an accelerated test that consists of passing hot exhaust gases through each purifier while oscillating it longitudinally on a test bench. Tests were conducted for 50 hours or until structural failure of the substrate.Diesel engines are commonly used in industrial equipment, exposing a catalytic converter in this application to a harsh environment. In practice, we have come across many cases where different substrate designs have failed under such difficult operating conditions. Observed structural failures of substrates in applications such as mining equipment prompted this investigation . The four substrates selected for testing covered differing design elements. Of the four substrates tested, the brazed, s-shaped, metallic design proved to be the most durable.