This action will address the agency’s technology review of the National Emission Standards for Hazardous Air Pollutants (NESHAP) for the Polyether Polyols (PEPO) Production industry (40 CFR part 63 subpart PPP). The PEPO NESHAP was promulgated pursuant to section 112(d) of the Clean Air Act (CAA) on June 1, 1999, and most recently, the agency conducted its residual risk and technology review (RTR) of the PEPO NESHAP on March 27, 2014. The PEPO NESHAP applies to major sources and regulate hazardous air pollutant (HAP) emissions resulting from the production of chemical products formed by the reaction of ethylene oxide, propylene oxide or other cyclic ethers with compounds having one or more reactive hydrogens. The HAP emission sources at PEPO production facilities include process vents, storage vessels, equipment leaks, wastewater, and heat exchange systems. The HAP emitted by the facilities producing polyether polyols include, but are not limited to, ethylene oxide, propylene oxide, hexane, and toluene. This action will implement the technology review requirements of CAA section 112(d)(6). CAA section 112(d)(6) requires the EPA to review and revise the NESHAP as necessary, taking into account developments in practices, processes and control technologies, no less often than every 8 years. The agency also plans to conduct a residual risk assessment under CAA section 112(f)(2) to consider risks from the polyether polyols production source category during its review.