Tetramethylsuccinonitrile or TMSN is an organic compound with the formula (C(CH3)2CN)2, classified as a dinitrile, and a colorless and odorless solid derived from 2,2'-azobis-isobutyronitrile, a common radical initiator in the manufacture of PVC: Because PVC is pervasive and can contain TMSN, the safety aspects of this dinitrile has generated interest.

[7] In regards to occupational exposures, the U.S. Occupational Safety and Health Administration and the U.S. National Institute for Occupational Safety and Health have set limits for dermal exposure at 3 mg/m3 over an eight-hour time-weighted average.

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