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On December 1, 2015, the EPA finalized the residual risk and technology review of the Petroleum Refinery source categories regulated national emission standards for hazardous air pollutants (80 FR 75178). As part of that action, the EPA also finalized a fenceline monitoring work practice standard to improve the management of fugitive emissions and finalized EPA Methods 325A/B (40 CFR part 63, Appendix A) to support the work practice. EPA’s Method 325A describes the collection of volatile organic compounds (VOCs) at or inside a facility property boundary or from fugitive and area emission sources using passive (diffusive) tube samplers (PS). The concentration of airborne VOCs at or near these potential fugitive- or area-emission sources may be determined using this method in combination with Method 325B. Companion Method 325B (Sampler Preparation and Analysis) describes preparation of sampling tubes, shipment and storage of exposed sampling tubes, and analysis of sampling tubes collected using either this passive sampling procedure or alternative active (pumped) sampling methods. More recently the use of Methods 325A/B were proposed to be used for a suite of compounds in the Hazardous Organic NESHAP or HON (88 FR 25080). Specifically, EPA proposed to require fenceline monitoring of benzene, chloroprene, 1,3-butadiene, and ethylene dichloride measured in accordance with Methods 325A/B and indicated that EPA would be revising EPA Method 325B to incorporate new information on uptake rates and to incorporate the sorbents (88 FR 25143). The EPA is proposing to revise Methods 325 A and B to incorporate new information on uptake rates, to incorporate the sorbents, and to reflect current laboratory best practices.