Witnesses - Incriminating Testimony; Perjury

No witness shall be excused from attending or testifying or from producing books, papers, records, accounts, and other documents before the department or in obedience to the subpoena issued by or in the name of the department on the ground or for the reason that the testimony, documentary or otherwise, required of him may tend to incriminate him or subject him to penalty or forfeiture. But no person shall be prosecuted or subject to any penalty or forfeiture for or on account of any transaction, matter, or thing concerning which he may testify or produce evidence, documentary or otherwise, before the commission or in obedience to its subpoena, but no person so testifying shall be exempt from prosecution and punishment for perjury committed in so testifying.