NTSB Safety Recommendation P-19-001

NTSB safety recommendation P-19-001.

TO THE PIPELINE AND HAZARDOUS MATERIALS SAFETY ADMINISTRATION: Require that all new service regulators be installed outside occupied structures.

Priority: CLASS II

Overall Status: Open Acceptable Alternate Response

Issued Date: 2019-06-10

Synopsis: On August 10, 2016, at 11:51 p.m., eastern daylight time, a 14-unit apartment building, located at 8701 Arliss Street, in the unincorporated community of Silver Spring, in Montgomery County, Maryland, partially collapsed due to a natural gas-fueled explosion and fire. The explosion and fire also heavily damaged an adjacent apartment building, 8703 Arliss Street, which shared a common wall with building 8701. As a result of this accident, 7 residents died, 65 residents were transported to the hospital, and 3 firefighters were treated and released from the hospital. The damage from the accident exceeded $1 million. The following are safety issues in this accident: • the location and inspection of service regulators within a structure • the inspection of the gas meter assembly • the notification of the natural gas odor to Washington Gas Light Company • the detection of natural gas through odorants and methane

Probable Cause: The National Transportation Safety Board determines that the probable cause of the explosion in building 8701 of the Flower Branch apartment complex was the failure of an indoor mercury service regulator with an unconnected vent line that allowed natural gas into the meter room where it accumulated and ignited from an unknown ignition source. Contributing to the accident was the location of the mercury service regulators where leak detection by odor was not readily available.

Keywords: Hazmat

Ntsbnumber: DCA16FP003

Report Number: PAR-19-01

Addressee Name: PHMSA

Addressee Status: Open Acceptable Alternate Response

Addressee Acronym: PHMSA

Addressee Organization Type: G-Federal Government

Communication Date: 2019-06-10

Communication Type: Transmittal Letter

Communication Contents: On April 24, 2019, the National Transportation Safety Board (NTSB) adopted its report, Building Explosion and Fire, Silver Spring, Maryland, August 10, 2016, NTSB/PAR-19/01. The details of this accident investigation and the resulting safety recommendations may be found in the attached report, which can also be accessed at http://www.ntsb.gov. As a result of this investigation, the NTSB identified the following safety issues: • The location and inspection of service regulators within a structure. • The inspection of the gas meter assembly. • The notification of the natural gas odor to Washington Gas Light Company. • The detection of natural gas through odorants and methane. Accordingly, the NTSB makes the following safety recommendations to the Pipeline and Hazardous Materials Safety Administration (PHMSA). Additional information regarding these recommendations can be found in the noted sections of the report. • Require that all new service regulators be installed outside occupied structures. (P-19-001) (See section 2.3.10.) • Require existing interior service regulators be relocated outside occupied structures whenever the gas service line, meter, or regulator is replaced. In addition, multifamily structures should be prioritized over single-family dwellings. (P-19-002) (See section 2.3.10.) The NTSB is vitally interested in these recommendations because they are designed to prevent accidents and save lives. We would appreciate a response within 90 days, detailing the actions you have taken or intend to take to implement these recommendations. When replying, please refer to the safety recommendations by number. We encourage you to submit your response to correspondence@ntsb.gov. If your reply exceeds 20 MB, including attachments, please e-mail us at the same address for instructions on how to send larger documents. Please do not submit both an electronic copy and a hard copy of the same response.

Addressee Acronym: PHMSA

Addressee Organization Type: G-Federal Government

Communication Date: 2020-02-11

Communication Type: Official Correspondence

Communication Contents: We appreciate your staff meeting with our staff on August 12, 2019, to discuss these recommendations. As discussed during the meeting, you believe that, in some cases, there are compelling safety reasons that justify placing service regulators inside a new or renovated occupied structure. Among these reasons is that service regulators located outside are at risk of damage from vehicular traffic. Your data showed that, from 2005 through 2018, gas distribution pipeline system releases resulted in a fatality or injury requiring hospitalization 372 times. Of these releases, 18 percent were caused by vehicular damage to meter and regulator sets located outside. As a result, you believe that operators should be allowed to evaluate each service installation to determine the appropriate location of the service regulators. During the August meeting, your staff said that developing a cost–benefit analysis showing a positive cost benefit, as required by the Office of Management and Budget (OMB) for all new and revised federal regulations, would be difficult or impossible. Your staff also argued that the intended results of these recommendations would be achieved without developing and issuing a new requirement. Because your existing regulations for indoor regulators are more stringent than for outdoor regulators, locating service meter and regulator sets inside structures is more costly and presents access challenges for operators. As a result, even without a requirement for placement outside, most new or renovated regulators are placed outside unless no safe and suitable outside space exists. For these reasons, you believe that enacting the recommended regulations would be, at best, difficult and time consuming. In comparison, because of existing regulations and policies for inside regulators, the intended results will be achieved faster than waiting for the completion of rulemaking. To encourage operators to move service units outdoors whenever possible, you plan to change your distribution inspection forms to emphasize compliance with existing service regulator requirements, and to revise the state program evaluation form to verify that states check operator compliance with your regulations for inside regulators. You also plan to review and emphasize current requirements for inside meters and regulators with operators, and you will issue an advisory bulletin alerting operators to the existing requirements for inside meters and regulators. To help operators recover the costs of moving service units outside, you plan to encourage states to provide a rate rider. During the August meeting, our staff pointed out that these activities might represent an acceptable alternate action to satisfy these recommendations if you could provide data showing that the actions were achieving similar results to a regulation. To provide this data, you plan to work with the National Association of Pipeline Safety Representatives to determine a baseline for the number of inside regulators, and then annually track this data to determine the rate of reduction in inside regulators. You would then submit your findings to us 1 year after implementing your plan. We do not evaluate cost–benefit considerations when we issue safety recommendations; our only criterion is that the recommended action addresses a safety issue that we found during our accident investigation. We issued Safety Recommendations P-19-1 and -2 based our finding in the Silver Spring investigation that, had service regulators been located outside building 8701 (where the explosion occurred), the explosion would have been avoided because gas would have vented to the atmosphere and dissipated. We are encouraged that you have developed an alternative that will not be subject to OMB review but will achieve similar results, in potentially less time than the recommended action. We commend you for developing data to show the success of your alternative, and your willingness to share this data with us. However, rather than determining that the recommended actions have been completed based on a 1-year review, we believe that you should collect this data and evaluate it annually over several years to ensure that positive trends continue and to evaluate whether your alternative action produces results equivalent to those that would come from a regulation. Your alternative action should include continuing analysis of the data that you collect to ensure that it shows sustained progress in moving existing indoor regulator sets outside whenever possible, and development of a revised planned action if the data does not show that trend continuing. Pending implementation of your plan to encourage operators to voluntarily locate service regulators outside of occupied structures for new and existing installations, our review of your data demonstrating that the plan is successful, and development of a revised plan if the data do not show that the alternative is achieving the same results as a regulation would, Safety Recommendations P 19-1 and -2 are classified OPEN--ACCEPTABLE ALTERNATE RESPONSE.

Addressee Acronym: PHMSA

Addressee Organization Type: G-Federal Government

Communication Date: 2022-05-02

Communication Type: Official Correspondence

Communication Contents: We appreciate your staff meeting with our staff on August 12, 2019, to discuss these recommendations. During that meeting, your staff said that developing a cost–benefit analysis showing a positive cost benefit, as required by the OMB for all new and revised federal regulations, would be difficult or impossible. Your staff also asserted that the intended results of these recommendations could be achieved without developing and issuing a new requirement. Because your existing regulations for indoor regulators are more stringent than for outdoor regulators, locating service meter and regulator sets inside structures is more costly and presents access challenges for operators. As a result, even without a requirement for placement outside, most new or renovated regulators are placed outside unless no safe and suitable outside space exists. For these reasons, you believe that enacting the recommended regulations would be, at best, difficult and time consuming. In comparison, PHMSA proposed an alternative approach that would achieve the intended results faster than waiting for the completion of rulemaking. Your alternative plan encourages operators to move service units outdoors whenever possible by changing your distribution inspection forms to emphasize compliance with the existing more restrictive regulations for inside regulators, and by revising the state program evaluation form to verify that states check operator compliance with PHMSA regulations for inside regulators. You also planned to review and emphasize current requirements for inside meters and regulators with operators and issue an ADB alerting operators to the existing requirements for inside meters and regulators. To help operators recover the costs of moving service units outside, you planned to encourage states to provide a rate rider. We have previously said that your planned response might be an acceptable alternate action to satisfy these recommendations if you could provide data showing that the actions were achieving similar results to a regulation. To provide this data, you planned to work with the National Association of Pipeline Safety Representatives to determine a baseline for the number of inside regulators, and then annually track this data to determine the rate of reduction in inside regulators. You would then submit your findings to us. We replied that PHMSA should collect this data and evaluate it annually over several years to ensure that positive trends continue and to evaluate whether your alternative action produces results equivalent to those that would come from a regulation. Your alternative action should include continuing analysis of the data that you collect to ensure that it shows sustained progress in moving existing indoor regulator sets outside whenever possible, and development of a revised planned action if the data does not show that trend continuing. We note from your recent letter that you have taken the following steps to further your proposed alternative actions: • In February 2020, you included a question in your Pipeline Safety State Program Evaluation Form to verify that states are checking operator compliance with regulations for inside service regulators. • In June 2020, you updated your Gas Distribution Inspection Form to guide federal and state inspectors to review operators’ compliance with the regulations relating to service regulators. • In September 2020, you issued an ADB alerting owners and operators of natural gas distribution pipelines about the requirements of the current regulations and the consequences of inside meters and regulators failing. In the same month, you sent a letter to all state ratemaking authorities encouraging them to consider having a rate rider to help recover the cost of moving inside meters and regulators outside. We further note that you are funding a research project that will evaluate technologies and procedures for retrofitting regulators located inside occupied structures to improve their safety. The research will develop a decision-making approach for pipeline operators to identify regulator/piping assemblies that could be replaced or relocated outdoors, and those where remediation, instead of relocation, would provide a similar level of safety to outdoor installations. Additionally, we note that you funded a related research project to evaluate new “vent-limiting” service regulators with a smaller footprint and to consider if minimum clearance distances from building openings could be safely decreased for these service regulators, making them suitable for use outdoors where there is limited space. This research project will provide information to pipeline regulators and stakeholders regarding alternative technology that could allow for a greater number of service regulators to be installed outside occupied structures. We appreciate this update on the steps you have completed. We ask that in your next update, you provide any data that you have showing that your alternative approach has been effective. Pending completion of your plan to encourage operators to voluntarily locate service regulators outside of occupied structures for new and existing installations, our review of your data demonstrating that the plan is successful, and development of a revised plan if the data do not show that the alternative is achieving the same results as a regulation, Safety Recommendations P 19-1 and -2 remain classified OPEN-- ACCEPTABLE ALTERNATE RESPONSE.

Addressee Acronym: PHMSA

Addressee Organization Type: G-Federal Government

Communication Date: 2022-01-14

Communication Type: Official Correspondence

Communication Contents: -From Tristan H. Brown, Deputy Administrator: PHMSA appreciates NTSB’s classification of this recommendation as Open—Acceptable Alternate Response based on PHMSA’s proposal to implement alternative actions. In February 2020, PHMSA included a question in its Pipeline Safety State Program Evaluation Form, used to evaluate the performance of its state partners’ pipeline safety programs, to verify that states are checking operator compliance with regulations for inside service regulators. In June 2020, PHMSA updated its gas distribution inspection form to include questions that more clearly guide federal and state inspectors to review operators’ compliance with the regulations relating to service regulators. Inspectors are also reviewing operators’ operation and maintenance procedures required by regulations relative to the placement of service regulators. In September 2020, PHMSA issued an ADB alerting owners and operators of natural gas distribution pipelines about the requirements of the current regulations and the consequences of failures of inside meters and regulators. In the same month, PHMSA sent a letter to all state ratemaking authorities encouraging them to consider having a rate rider to help recover the cost of moving inside meters and regulators outside, when it can be done without comprising pipeline safety. PHMSA is conducting R&D in this area as well. PHMSA awarded a research project in September 2020 that will deliver recommendations of technologies and procedures for retrofitting regulators located inside occupied structures to improve their safety.11 Additionally, the researcher will develop a decision-making approach for pipeline operators to identify regulator/piping assemblies that could be replaced or relocated outdoors, and those where remediation, instead of relocation, would provide a similar level of safety to outdoor installations. This research project was completed in December 2021, and the final report is anticipated to be available by February 2022. PHMSA expects the results to offer valuable information regarding the placement of service regulators and on potential retrofitting alternatives, when relocating a service regulator outside occupied structures may not be possible. Additionally, PHMSA funded a related research project in September 2021 to evaluate new “vent-limiting” service regulators with a smaller footprint and to consider whether minimum clearance distances from building openings could be safely decreased for these service regulators, making them suitable for use outdoors where there is limited space. The research project is expected to be completed by March 2023 and will offer valuable information to pipeline regulators and stakeholders regarding alternative technology that could potentially allow for a greater number of service regulators to be installed outside occupied structures.

Addressee Acronym: PHMSA

Addressee Organization Type: G-Federal Government

Communication Date: 2019-09-05

Communication Type: Official Correspondence

Communication Contents: -From Howard R. Elliott, Administrator: The mission of PHMSA is to protect people and the environment by advancing the safe transportation of energy and other hazardous materials that are essential to our daily lives. PHMSA shares the NTSB' s commitment to preventing pipeline accidents. PHMSA has a long history of cooperating and collaborating with the NTSB, and we take our responsibility to address all of NTSB's recommendations seriously. While PHMSA' s regulations allow service regulators to be located inside or outside structures, the requirements for indoor regulators are more stringent than for those located outdoors. Specifically, 49 CFR § 192.355(b) requires service regulator vents to terminate outdoors; § 192.357(d) requires regulators that might release gas to be vented to the outside atmosphere; and § 192.353 requires each service regulator to be located in a readily accessible location, and that if service regulators are installed in a building they must be located as near as practical to the service line entrance to the building. In general, locating service meter and regulator sets inside structures is more costly and presents access challenges for operators. Today, most sets are placed outside unless no safe and suitable space exists outside. PHMSA' s regulations also include requirements that operators conduct leakage surveys of their systems, including service regulators located inside or outside a building. In scheduling these, they may consider the nature of their operations and the local conditions, but at a minimum they must conduct surveys: (1) in business districts at intervals not exceeding 15 months, but at least once each calendar year; and (2) outside business districts as frequently as necessary, but at least once every five calendar years at intervals not exceeding 63 months (See § 192.723). In addition,§ 192.481 requires operators to inspect meters and regulators for atmospheric corrosion at least once every 3 years, at intervals not to exceed 39 months. Requiring service regulators and meter sets to be located outside could have unintended consequences. When located outside, regulator and meter sets are at risk of damage from vehicular traffic. From 2005 through 2018, gas distribution pipeline system releases resulted in a fatality or injury requiring hospitalization 3 72 times. Of these releases, 18% were caused by vehicular damage to meter and regulator sets located outside. Operators should be allowed to evaluate each service installation to determine the appropriate location of the service regulators. Further, in our analysis to respond to the above Recommendations, PHMSA assumed that operators would incur no additional costs to place service regulators outside for new construction (P-19-001 ). However, PHMSA estimates that implementing Recommendation P-19-002 could involve inside regulators serving approximately 13.9 million existing occupied structures, at an estimated cost of $520 million during the first year. This makes it unlikely that the estimated cost of relocating service regulators outdoors would pass the statutory cost/benefit requirements for rulemaking. To arrive at this conclusion, PHMSA used 2018 data collected through PHMSA's Gas Distribution Annual Reports. PHMSA's preliminary analysis of this data indicates that there is a total of 69,330,683 service lines operated by 1,462 pipeline operators nationally. Based on estimates provided by gas utility companies and the National Association of Pipeline Safety Representatives, as much as 20 percent of occupied structures are likely to be served by regulators located inside. PHMSA also assumes a 0.5 percent replacement rate each year, leading to recurring annual costs of a similar yet decreasing magnitude. As NTSB is aware, completing rulemakings takes time, as it is an iterative process that is designed to encourage maximum participation by all stakeholders, thus ensuring comprehensive rules that protect the public and stand up to cost/benefit scrutiny. For the reasons stated above, PHMSA believes the intent of both NTSB Recommendations can be achieved quickly by implementing the following alternatives: • Add questions and guidance to PHMSA's distribution inspection forms that are used by PHMSA and state pipeline safety inspectors to clearly guide them to review operators' compliance with our regulations relating to service regulators, and to have them review operator's Operation and Maintenance procedures relative to the placement of service regulators; • Modify the State Program Evaluation Form to include a question verifying that states are checking operator compliance with our regulations for inside regulators; • Review current requirements for inside meter/regulators with operators at all state pipeline safety seminars beginning in 2020; • Issue an Advisory Bulletin alerting operators of the requirements for inside meter/regulators, including leakage surveys, noting that if access is an issue to properly check and maintain inside regulators, operators must do what is necessary to have the customer provide access to check the regulator and conduct the leak or atmospheric corrosion survey; • Encourage states to provide a rate rider to move regulators outside where possible; and • Support research and development to improve service regulator design to facilitate placement in areas where very limited outside space exists. PHMSA proposes to track the efficacy of these alternative actions by: • Working with the National Association of Pipeline Safety Representatives to determine a baseline for the number of inside regulators. PHMSA would then annually track this data to determine the rate of reduction in inside regulators; • Reviewing incident data to identify potential trends for Material/Weld/Equipment failures involving inside regulators; and • Reviewing Federal and state inspection and enforcement relative to compliance with the regulations. PHMSA proposes to submit our findings to NTSB one year after the implementation of the above plan. PHMSA is committed to continuously help improve the safety of our nation's pipeline system. Towards that end, we take our responsibility to address all NTSB recommendations seriously. PHMSA is requesting that NTSB accept our alternative actions to address the intent of Recommendations P-19-001 and P-19-002. My staff and I would be pleased to meet with you to further discuss this proposal. We look forward to a favorable response.

Addressee Acronym: PHMSA

Addressee Organization Type: G-Federal Government

Communication Date: 2025-09-12

Communication Type: Official Correspondence

Communication Contents: -From Ben Kochman, Acting Administrator: As discussed below, Safety Recommendation P-19-1 urged PHMSA to require new regulators be installed outside occupied structures. The term “regulator” is used in this letter for plain language to mean regulator, service regulator, meter and regulator, meter/regulator set, customer meter, meter set, and gas service regulator, except when referencing a title. Safety Recommendation P-19-2 further urged PHMSA to require existing interior regulators be relocated outside occupied structures whenever the gas service line, meter, or regulator is replaced. PHMSA has taken action to respond to both recommendations. PHMSA’s Actions to Address Safety Recommendation P-19-1 and P-19-2 On January 14, 2022, PHMSA proposed to address Safety Recommendations P-19-1 and P-19-2 through alternative actions. By correspondence dated May 2, 2022, NTSB classified these Safety Recommendations as “Open-Acceptable Alternate Response.” PHMSA is pleased to inform NTSB of the following completed actions: State Program Evaluation Starting in February 2020, PHMSA included a question in its Pipeline Safety Gas State Program Evaluation to verify that States are checking operator compliance with regulations for inside regulators. PHMSA evaluates the performance of its State partners through annual program evaluations. Inspection Questions On June 15, 2020, PHMSA updated five questions in its Inspection Assistant (IA) related to inside regulators to support Federal and State inspector assessments of gas distribution operators during related inspections. Inspection Assistant (IA) refers to the PHMSA software application that is used before, during, and after an inspection to help collect new risk data, plan an inspection, document the results, and ensure that proper procedures are followed. IA is used by PHMSA and several of PHMSA’s State partners. Advisory Bulletin On September 29, 2020, PHMSA issued an advisory bulletin [ADB-2020-01] to owners and operators of gas distribution systems reviewing details of the August 10, 2016 incident. The advisory bulletin shared NTSB’s investigation findings and recommendations, as well as the consequences of failures of inside regulators. Pipeline Safety: Inside Meters and Regulators, 85 FR 61101 (Sept, 29, 2020), https://www.federalregister.gov/documents/2020/09/29/2020-21507/pipeline-safety-inside-meters-and-regulators. The advisory bulletin reminds operators of existing Federal pipeline safety regulations, including integrity management regulations for distribution systems to reduce the risks associated with failures of inside regulators. As of August 2025, the advisory bulletin has been downloaded or viewed more than 3,900 times from the Federal Register. Indoor Regulator Research and Development PHMSA sponsored two research and development (R&D) projects responsive to Safety Recommendations P-19-1 and P-19-2. The R&D projects focused on improving operators’ ability to install inside regulators outside and providing best practices for retrofitting inside regulators and associated piping to maintain the same level of safety as a regulator installed outside. • Procedures for Retrofitting Indoor Gas Service Regulators: Completed in 2022, this project addresses NTSB recommendations aimed at reducing the consequence of failure involving regulators. See https://primis.phmsa.dot.gov/matrix/PrjHome.rdm?prj=916 The project provided “best practices for the inspection, recording, and maintenance of gas regulators and utility indoor piping systems” and provided “a consistent decision-making tool when a [regulator] needs to stay inside.” The project also provided recommended practices for gas distribution operators with inside regulators to consider in their distribution integrity management program. • Design and Placement of Compact Service Regulators: Completed in 2024, the project’s objective was to “provide natural gas utilities with data for additional options for the safe, outside installation of [regulators].” See https://primis.phmsa.dot.gov/matrix/PrjHome.rdm?prj=945 The project “reviewed existing practices and performed comparative [regulator] testing that resulted in data that can be used for guidance to the natural gas industry on ‘vent-limiting’ [regulators]. The data results may provide more options for a gas utility to install or move the [regulator] to the outside of the structure. . . Experimental testing has determined that ‘vent-limiting’ [regulators] offer more options for outside installation by having a smaller footprint that includes the ability to install at reduced clearance as compared to traditional internal relief valve (IRV) [regulators].” Outreach with States/National Association of Pipeline Safety Representatives In March 2020, PHMSA provided a presentation template for States to use during seminars and meetings with pipeline operators. This template was developed by PHMSA and the National Association of Pipeline Safety Representatives (NAPSR) to help ensure that compliance with regulations for inside meters remains a reoccurring topic during operator meetings. In September 2020, PHMSA sent a letter to all State rate-making authorities, encouraging them to consider having a rate rider to recover costs associated with moving inside regulators outside when it can be done without compromising pipeline safety. On June 6, 2025, PHMSA shared with NAPSR the Procedures for Retrofitting Indoor Gas Service Regulators and Design and Placement of Compact Service Regulators R&D projects for review and dissemination to State-regulated operators. Effectiveness of Alternate Actions PHMSA analyzed its incident data from 2016 through June 2025 to assess its effectiveness in achieving the safety intent of NTSB Safety Recommendations P-19-1 and P-19-2. Since 2016, gas distribution incidents involving inside regulators have declined in total number per year and as a percentage of all gas distribution incidents. See https://www.phmsa.dot.gov/data-and-statistics/pipeline/distribution-transmission-gathering-lng-and-liquid-accident-and-incident-data (accessed Jun. 12, 2025). The analysis used Gas Distribution Incident Data, filtered by date range (2016 through June 2025) and limited incidents to where “SYSTEM_PART_INVOLVED” contained “INSIDE METER/REGULATOR SET.” External data sources also indicate a decline in the use of inside regulators. A NAPSR survey of States, Washington, D.C., and Puerto Rico found: • 37 percent of respondents have no inside regulators. • 40 percent of respondents have rate recovery, other incentive programs, or statutory requirements to promote and support relocating inside regulators outside. In addition, between January 2019 and May 2025, about 51 percent of States, Washington, D.C., and Puerto Rico with inside regulators issued approximately 900 enforcement actions/violations related to regulatory requirements for inside regulators. The American Gas Association (AGA) collects unofficial, voluntary data from their member operators on the number of inside regulators. According to AGA, inside regulators accounted for about 17 percent of its member operators’ regulators in 2019 and about 11 percent in 2023. This represents a decrease of about 35 percent of its member operators’ inside regulators. REQUEST FOR CLOSURE OF RECOMMENDATIONS P-19-1 AND P-19-2 PHMSA takes its responsibility to address all NTSB recommendations seriously. Based on PHMSA’s actions as discussed above, PHMSA requests that Safety Recommendations P-19-1 and P-19-2 be classified as “Closed—Acceptable Alternate Action.” PHMSA looks forward to working with NTSB as it continues to strive to ensure the safe and reliable operation of the Nation’s pipeline transportation system in support of the Administration’s priorities.

Addressee Acronym: PHMSA

Addressee Organization Type: G-Federal Government

Communication Date: 2019-12-03

Communication Type: Official Correspondence

Communication Contents: -From Howard R. Elliott, Administrator: PHMSA proposed an alternative approach for this recommendation on September 5, 2019, and looks forward to NTSB's response.