Final answer:
The EPA final rule's technician certification requirements took effect on December 28, 2015, following its signing on October 1, 2015.
Step-by-step explanation:
Under the EPA final rule, signed on October 1, 2015, the technician certification requirements officially became effective on December 28, 2015. While the 2008 ozone (O3) standards remained in effect in certain areas, there was a revocation of the previous standards with a transition to the current (2015) standards, which was to be addressed in the implementation rule for the current standards.
The Environmental Protection Agency (EPA) has a history of implementing regulations aimed at protecting the environment and public health, which sometimes result in political compromises due to the complexities of the legislative process and the different interests of various stakeholders, such as existing firms and new producers.