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2 Posts authored by: aing Employee


Yesterday morning, an explosion, most likely involving natural gas, ripped through three rowhouses in northwest Baltimore, leaving two dead and seven more transported to hospitals. The blast occurred on the 4-year anniversary of another Maryland natural gas explosion, which killed seven and injured nearly ten times as many in the city of Silver Springs in 2016. While the cause of this recent explosion remains under investigation, the damages sustained in the Baltimore incident are reminiscent of similar fuel gas explosions we’ve seen in recent years in the Merrimack Valley region of Massachusetts in 2018 and Farmington, Maine last September.

Fuel gases include natural gas, manufactured gas, liquefied petroleum (LP) gas (typically propane & butane), or mixtures of these gases that are distributed commercially and used in gas appliances for cooking and heating. There are several different codes, standards, and regulations here in the U.S that govern the safe use of fuel gas systems. The codes, standards, and regulations apply to both the fuel gas being used and those responsible for each part of the system.

For natural gas systems, the utility company (in this case Baltimore Gas and Electric) is responsible for the transmission lines and piping up to the service meter at the customer’s house. The Department of Transportation (DOT) and The Pipeline and Hazardous Materials Safety Administration (PHMSA) regulate gas utilities and jurisdictional requirements are listed under Title 49 Code of Federal Regulations (CFR). Responsibility for gas from the outlet of the service meter to the appropriate gas appliance lies with the customer and is addressed within NFPA 54 National Fuel Gas Code.


NFPA research found that an estimated 4,200 home structure fires per year were started with the ignition of natural gas and caused an average of 40 deaths.

Looking back at recent incidents, we know that the Merrimack Valley fire and explosions was caused by an over-pressurization in the utility gas transmission lines which caused damage to customer-owned equipment. One person was killed, dozens of explosions and fires damaged more than 40 homes, and 30,000 residents and business owners were forced to evacuate. In the case of the LEAP Building explosion in Maine, gas piping outside the home was punctured by a drilling operation that caused gas to migrate into the basement of the building. That incident killed one firefighter, injured others and destroyed a non-profit building.

Combustion requires three things - fuel, oxygen, and an ignition source. In the case of natural gas explosions, the leaking gas is the fuel. Ambient air serves as the oxygen, which in the right proportion with the fuel, forms an ignitable mixture. The last part of the triangle is an ignition source to spark the vapor/air mixture. When gas enters an occupancy (either from the outside or from an appliance leak within the home), simple gestures like turning on the stove or switching on a light switch can serve as the ignition source.

Both natural gas and LP-Gas are colorless and odorless, which makes detecting a leak difficult. When fuel gases are used for consumer application, they are treated with an odorant that emits a distinct smell and helps to alert parties nearby that a leak has occurred. Despite odorization efforts, odor fades and not everyone can detect odor readily. Based on incidents like yesterday, various parties have asked for the development and installation of gas detection devices for residential applications.

NFPA 715, Standard for the Installation of Fuel Gases Detection and Warning Equipment is in the early developmental stages prior to beginning full public review. NFPA 715 addresses recommendations made by the National Transportation Safety Board’s (NTSB) investigation following the Silver Springs explosion; it will cover the selection, design, application, installation, location, performance, inspection, testing, and maintenance of fuel gas detection and warning equipment in buildings and structures. The Standards Council decided to begin the full NFPA 715 revision process and invites stakeholders to submit public inputs at this point.

Additionally, the Fire Protection Research Foundation, the research affiliate of NFPA, will soon complete a report on combustible gas detector (CGD) placement that looks to use modeling work to justify requirements in NFPA 715 for the best location of CGD in order to ensure early and accurate detection of leaks.

The incident in Baltimore and the other events I have noted above underscore the need for sharing and understanding simple gas leak safety measures. Here are some that come to mind:


  • Prior to any construction work, be sure to contact Dig Safe or similar local authorities to prevent accidental damage to buried underground piping as digging is a frequent cause of damage to the main line before the meter.
  • If you smell gas – typically a rotten egg smell due to the mercaptan odorant - leave the area or building immediately.
  • Avoid possible ignition sources such as matches and lighters, light switches, flashlights, telephones, cell phones and other communication devices if you do smell that rotten egg smell. Do not start a car or ring doorbells either.
  • Get to a safe area and call 911 to report a gas leak. Then follow the instructions of any on-site emergency responders or utility employees, as they respond to the leak.


For more information on NFPA 54 or the proposed NFPA 715, visit

Some significant changes are on the horizon for NFPA 58, Liquefied Petroleum Gas Code. Although the changes that have been proposed so far in the code development process are not groundbreaking, they are worthy of your attention if the work you do is impacted by the requirements in this code.

One big change is still to be decided at an upcoming event. At the 2019 NFPA Technical Meeting in June, the 2020 edition of NFPA 58 will be up for any Certified Amending Motions (CAMs). This will be the second-to-last chance for any changes to be made to the document before it is issued by the NFPA Standards Council.

There is only one CAM on NFPA 58 and it’s on purging pipe systems to atmosphere. At the first draft meeting, the committee elected to change the procedures from what they are currently in the 2017 edition to the first draft language. This new language would require pipe purging of systems designed for 125 psig or less to be done in accordance with the requirements in NFPA 54, National Fuel Gas Code, and any systems of greater than 125 psig to be purged in accordance with NFPA 56, Standard for Fire and Explosion Prevention During Cleaning and Purging of Flammable Gas Piping Systems. The committee, however, at second draft changed the language to state that regardless of system operating pressure, the procedures of NFPA 54 must be followed. The CAM is looking to reject this change and send the document back to the same first draft language. What happens to the document next is up to the general body at the Technical Meeting.

There are a number of other changes that have happened to NFPA 58 that are almost finalized and are covered below. While none of these changes are groundbreaking for NFPA 58, they are significant enough to call out.

  • Chapter 12, which covers over-the-road motor vehicles fueled by LP-Gas, has been reorganized and revised to be more user-friendly.
  • Chapter 15, which covers operations and maintenance (O&M), has also been revised to be more user-friendly. Specifically, Chapter 15 has been revised to call out more O&M requirements in NFPA 58 rather than installation requirements as in previous editions. More importantly, Chapter 15 now excludes pipelines under the jurisdiction of the US Department of Transportation, as their O&M requirements are more stringent than the requirements of NFPA 58.
  • LP-Gas cylinders that are equipped with CGA 791 and CGA 793 connections are now required to have their valve face seal inspected before filling can occur, because it is possible that over time the face seal can become damaged from exposure to the weather or misuse. If any defects are found, then the cylinder is not permitted to be filled.
  • Fire extinguisher requirements in the 2017 edition were reorganized to be centrally located in Chapter 4. The 2020 edition has further revised the fire extinguisher requirements in order to bring them more in line with industry standards such as NFPA 10, Standard for Portable Fire Extinguishers. Doing so allows the user to select the most appropriate fire extinguisher for the type of fire they are anticipating to fight.

These changes are only some, but not all, of the upcoming revisions to the 2020 edition of NFPA 58. For a more detailed list, visit for a revisions fact sheet and information on how to get involved in the next cycle of NFPA 58.  

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