42 CFR §84.301

1. (a)Any CCER approval issued after April 9, 2012 must comply with the technical requirements of subpart O.
2. (b)The continued manufacturing, labeling, and sale of closed-circuit apparatus previously approved under subpart H is authorized for units required for use in underground coal mines pursuant to 30 CFR 75.1714-1.
3. (c)Any manufacturer-requested modification to a device approved under the subpart H technical requirements must comply with the subpart H technical requirements and address an identified worker safety or health concern to be granted an extension of the NIOSH approval. Major modifications to the configuration that will result in a new approval must meet and be issued approvals under the requirements of this subpart O.