Section 49.4174 - VOC emissions control requirements for dehydrators(a)Applicability. The VOC emissions control requirements of this section apply to each glycol dehydration unit located at an oil and natural gas source as identified in § 49.4169(b) where the source-wide potential for VOC emissions from the collection of all storage vessels, glycol dehydrators, and pneumatic pumps is equal to or greater than 4 tpy, as determined according to § 49.4173 . You must reevaluate the source-wide VOC emissions from the collection of all storage vessels, glycol dehydrators and pneumatic pumps for each modification to an existing source, as described in § 49.4173(a)(3) . Applicability for glycol dehydrators that began operation before February 6, 2023 must be determined using uncontrolled actual emissions. Applicability for glycol dehydrators that began operation on or after February 6, 2023 must be determined using potential to emit.(b)Exemptions. This section does not apply to glycol dehydration units subject to the emissions control requirements for glycol dehydration unit process vents in 40 CFR part 63, subpart HH.(c)VOC emissions control requirements. For each glycol dehydration unit, you must comply with the VOC emissions control requirements of paragraphs (c)(1) or (2) of this section.(1) You must reduce VOC emissions from each glycol dehydration unit process vent by at least 95.0 percent on a continuous basis according to paragraphs (c)(1)(i) and (ii) of this section. You must route all glycol dehydration unit process vent emissions through a closed-vent system that meets the conditions specified in § 49.4176(d) to: (i) An operating system designed to recover 100 percent of the emissions and recycle them for use in a process unit or incorporate them into a product; or(ii) An enclosed combustor or flare designed to reduce the mass content of VOC in the emissions vented to the device by at least 95.0 percent and operated as specified in § 49.4177 ; or(2) You must maintain the source-wide uncontrolled actual VOC emissions from the collection of all storage vessels, glycol dehydrators, and pneumatic pumps at an oil and natural gas source at less than 4 tpy for 12 consecutive months in accordance with the procedures specified in § 49.4173(c)(2) .