Professional Development Hours (PDH) are mandatory continuing education credits required for licensed engineers to maintain their Professional Engineer (PE) status. Typically, one PDH equates to one hour of instruction or study, with most states necessitating 15 to 30 PDHs every one to two years. These credits can be earned through various formats, including online courses, webinars, and in-person seminars, covering a wide range of engineering disciplines such as civil, mechanical, electrical, and environmental engineering.