What are the differences between a standard capsule and a DPI capsule?

There are two main differences between DPI capsules and standard capsules: microbial levels and lubricant levels. In order to avoid any risk of bacterial contamination during inhalation, the European pharmacopeia and the FDA require DPI suppliers to be compliant with a low level of microbes (EP 5.1.4 on microbiological requirements). Also, a lower level of lubricant is and keep a consistent level of  applied residual powder in the DPI capsule (Lubricant <500 ppm).