The purpose of this document is to provide considerations for modifications to the Occupational Safety and Health Administration (OSHA) air sampling method for TDI: OSHA Method 42. These modifications can help improve the ability of the method to sample and derivatize TDI. The information provided in this document is not a directive or an industry standard. The information is intended as guidance. Users should independently determine what constitutes an appropriate practice relative to their own needs and circumstances.