--- title: "EPA Refinery Rule: Fenceline Benzene Action Level | Aethair" description: "EPA Refinery Sector Rule: fenceline benzene action level (9 µg/m³ Δc), how Method 325 sampling works, who it applies to, and a recommended configuration." url: https://aethair.io/standards/epa_refinery_fenceline/ --- Compliance · US EPA # EPA Petroleum Refinery Sector Rule: fenceline benzene (40 CFR 63.658) Ambient air: petroleum refinery fenceline (USA) The EPA's Petroleum Refinery Sector Rule, finalized in 2015 as amendments to 40 CFR Part 63 Subpart CC, requires every petroleum refinery to monitor **benzene at its fenceline** under §63.658. Passive samplers around the property boundary collect benzene over contiguous **14-day periods**, and for each period the facility calculates **Δc, the highest minus the lowest fenceline concentration**. When the **annual average Δc, over the 26 most recent periods, exceeds 9 µg/m³**, the refinery must carry out a root cause analysis and corrective action. [Schedule a call](https://calendly.com/d/ctdd-mkr-v9v/aethair-demo-website) [Configure Refinery Sector Rule Monitoring](https://aethair.io/build/?params=btex\&setting=outdoor) At a glance **US EPA** Ambient air: petroleum refinery fenceline (USA) 1 parameter · 1 limit value [BTEX / speciated VOC](https://aethair.io/parameters/btex/) 1 device measures them all - **Thiamis** Defiant Technologies Specialty Air Analyzers [Official text from US EPA](https://www.ecfr.gov/current/title-40/chapter-I/subchapter-C/part-63/subpart-CC/section-63.658) The standard ## What the Refinery Sector Rule Requires The rule is a transparency and correction mechanism rather than an ambient limit: it targets the refinery's own contribution, measured as the difference across its fenceline, and it has made refinery fenceline data public, reported to the EPA quarterly since 2019. Limit values ## Refinery Sector Rule Limit Values Every value US EPA publishes for the parameter below, with its averaging period, as the standard states it. [**BTEX / speciated VOC** Gases & VOCs](https://aethair.io/parameters/btex/) **9 µg/m³** *Annual average Δc, fenceline* benzene; Δc is the highest minus the lowest 14-day fenceline sample, averaged over 26 periods; above it, root cause analysis and corrective action Who it applies to ## Who It Applies to Petroleum refineries subject to 40 CFR Part 63 Subpart CC across the United States. The number of samplers and their spacing follow EPA [Method 325A](https://aethair.io/standards/epa_method_325/), and the samples are analyzed under Method 325B. A refinery may use an approved alternative method, such as open-path monitoring, if it gives equal or better spatial coverage, and may use a site-specific monitoring plan to correct for near-field sources that are not its own. Monitoring ## How Monitoring Demonstrates Compliance Compliance rests on the passive sampler record: the 14-day samples, laboratory results, Δc for each period, and the rolling annual average against 9 µg/m³. Continuous monitoring does not replace that record, but it answers the questions the record raises: when concentrations rose, from which direction, and during which operations. That is the information a root cause analysis needs. Wind data belongs with every reading. [Customize this configuration](https://aethair.io/build/?params=btex\&setting=outdoor) ### Who measures each parameter | Parameter | Aethair PRO | Aethair IAQ | External | | - | - | - | - | | [BTEX / speciated VOC](https://aethair.io/parameters/btex/) | — | — | [1 instrument](https://aethair.io/parameters/btex/) via Thiamis | Devices ## Devices That Cover Refinery Sector Rule How much of this standard one Aethair monitor covers, followed by the third-party instruments in the sensor catalog that measure its parameters. Each connects to Environet through a Thiamis gateway, which adds whatever the monitor leaves out. Covers it on its own [**Defiant Technologies FROG** Specialty Air Analyzers](https://aethair.io/sensors/defiant-technologies-specialty-air-analyzers/) Solutions ## Solutions Judged Against Refinery Sector Rule ### [Oil & Gas / Petrochemical](https://aethair.io/solutions/oil-gas/) Fence-line VOC, H₂S, and methane leak detection [All solutions](https://aethair.io/solutions/) Article Library ## Articles on Refinery Sector Rule ### [Industrial Perimeter Air Quality Monitoring: Action Levels](https://aethair.io/resources/perimeter-air-quality-monitoring-guide/) What industrial perimeter monitoring requires at fenceline and construction sites: DER-10 CAMP action levels, EPA fenceline rules, and continuous records. ### [How to Choose an Air Quality Monitor: PRO, IAQ, or Thiamis](https://aethair.io/resources/choosing-aethair-monitoring-device/) Compare Aethair PRO, IAQ, and Thiamis to match the right device to your site, from commercial interiors to industrial and fenceline monitoring. [All articles](https://aethair.io/resources/) Questions ## Refinery Sector Rule FAQ What is the refinery fenceline benzene action level? 9 µg/m³, compared against the annual average of Δc (the highest minus the lowest fenceline sample in each 14-day period) over the 26 most recent periods. Above it, the refinery must investigate the root cause and take corrective action. How is refinery fenceline benzene sampled? With passive diffusive sorbent tubes deployed around the property boundary under EPA Method 325A, exposed for 14 days and analyzed in a laboratory under Method 325B. Can continuous monitors be used under the refinery rule? An approved alternative method, such as open-path monitoring, can replace samplers if it gives equal or better spatial coverage. Otherwise continuous monitoring supports the program (showing when and from where concentrations rose) rather than replacing the passive samplers.