Operational Procedures: Tactical Response to Explosive Gases

Training Notebook

SOLID OPERATIONAL POLICIES, procedures, strategies, and tactics contained in our standard operating procedures (SOPs) will result in successful execution of firefighters’ mission of life safety at releases of explosive gases such as natural gas (methane) and propane.

Gas leaks are very common calls for all fire departments across the United States. However, our SOPs often lack the clear executable strategic and tactical guidance to ensure rapid and efficient success in accomplishing our mission of life safety.

Often, our SOPs are not based on gas industry best practices. Fire department leaders are responsible for providing quality SOPs to subordinates and for executing those SOPs as incident commanders (ICs). It is the member’s responsibility to be well trained to be able to execute the procedures and tactics outlined in the SOPs. Our SOPs must contain the following critical points:

Operational policies.
Procedures.
Strategies.
Tactics.

This article will cover how to best incorporate the points listed above as you write or fine-tune your SOPs for responses to explosive gases.

When I present across the United States, almost every station I visit shares stories about close calls or building explosions that resulted from seemingly routine gas calls. It’s clear that we need to recall the following critical points about our explosive gas detectors so we can make good decisions during size-up (photo 1). These decisions will affect our choice of strategy and tactics.

1. Underground gas leaks are among the most dangerous and difficult to size up and resolve. *(Photo by Dominick D’Alisera.)*

Here are a few examples:

Your four-gas monitor has a clip on the back. It is a personal monitor—not an explosive gas detector. Gas utility technicians don’t use these.
Your catalytic bead flammable gas sensor in your four-gas monitor cannot detect low levels of gas in the 1-2% lower explosive limit (LEL) range.
Catalytic bead sensors in your four-gas monitor can be poisoned by vehicle exhaust and silicon-containing compounds like vinyl cleaners.
Metal oxide-based explosive gas sensors can detect very low levels of flammable gases, are inexpensive, and are used by most utility companies in the United States.
Many major fire departments in the United States pair up a metal oxide-based sensor with their four-gas monitor.
Common sample points for inside gas odors are inside the main door and the point of entry for pipes in the basement.
Your SOP must contain both action levels and kill box dimensions. The action level is the percentage of the LEL that your department has determined to initiate mandatory evacuation of civilians and firefighters. The kill box, like the collapse zone, is the area around or in the building where you will likely be killed if things go bad.
Carbon monoxide sensors are often cross sensitive to other explosive gases such as hydrogen, propane, and acetylene.
Read the manual to learn how to use your instrument and understand its strengths and weaknesses.

Good SOPs

All that technical and procedural background is wasted if you don’t apply it through correct overall strategy and tactical decisions and actions. A good SOP will include these, and they’ll be clearly spelled out. The first section of a good SOP should feature the operational policies.

Operational policies are the rules you expect your officers and members to use to execute a call. The policy section must establish objectives while simultaneously allowing your officers and members to use their experience, expertise, and judgment within the established framework.

The procedure section provides general step-by-step actions, much like a medical protocol. These are based on your local gas industry’s practices. Strategies (objectives) and tactics (execution of strategy) must be clear and provide officers with overarching goals and objectives. Tactical actions provide guidance to members who will execute the strategies. Good SOPs need to have strategies and tactics for the six major types of natural gas emergencies.

Operational Policies, Procedures, Strategies, and Tactics

Complete and quality SOPs will lead you to fireground success in the mission of protecting civilians’ and firefighters’ life safety at gas leaks. This technical skill set is the critical prerequisite to developing an SOP that provides first-due officers and members with the guidance they need. Capturing and conveying operational policies, procedures, strategies, and tactics into an SOP is challenging. Following are a few steps that will help you.

It is important to understand why your current SOPs may be inadequate, leading to less-than-optimal and inefficient responses. Weak SOPs also lead to needless risk taking by our members. Good SOPs will resolve weaknesses in our overall response to gas leaks. Remember: Your SOP must contain and clearly convey the information, procedures strategies, and tactics you want your officers and members to execute at gas leaks. Some key items below will help you understand why your current SOPs may be weak and how to strengthen your new SOPs.

With a grasp of critical technical aspects, along with an understanding of why current SOPs may be weak, we can move forward to drafting, testing, and producing excellent operational procedures for releases of explosive gases.

Critical Concepts

Training gap: Even with all our required training curricula, many departments receive insufficient training on response procedures, use of air monitoring equipment/proce- dures, sampling locations, the interpretation of air monitoring results, size-up procedures, and tactical decision making for explosive gas emergencies. Add annual, specific, and detailed training requirements to strengthen your SOP.

Mission: The fire department’s mission at gas emergencies is life safety. It is not finding and fixing the leak. This point is important for you to clarify, as many members often misunderstand it.

Kill box: This is like the collapse zone. It’s where we are likely to have fatal or serious injuries if the explosive gas ignites. Many fire departments initially position first-due units too close to the physical location of the gas leak. Include specific guidance for keeping members and apparatus out of the kill box.

Explosive gas detectors: Most fire departments use a four-gas meter that is set up as a personal monitor for confined space rescue. Many firefighters are not well trained on their instrument, have never seen its alarm go off, don’t know what it reads at 100% LEL, and cannot determine the level of danger or other information the meter may be indicating. Include specific hands-on training with live gas and your meters so officers and members are proficient.

Action level: Many SOPs do not have levels of gas requiring mandatory evacuation of civilians and firefighters. Include specific levels for mandatory evacuation of civilians and fire department members.

Train like you fight: Most fire departments do not train with the gas technicians who will respond to releases of explosive gas with you. Many states require gas utilities to train local fire departments. Smart gas utilities will invite you and your members to train at their site, which often contains live gas leak training scenarios. Train with the gas technicians you will work with at releases of explosive gas.

Trust but verify: You are responsible for civilian and member life safety. You are not responsible for the gas technician. The fire department has a life safety mission. The gas technician has the find-and-fix mission and can be a valuable resource to you. The gas technician may be inexperienced, not familiar with the utility’s own procedures, or simply just overcomplacent. You need to know the procedures so the gas technician does not put you and your members in dangerous situations.

Six Types of Natural Gas Leaks

Your gas utility has a procedure for each type of leak and you should have one as well. Each leak or odor scenario is a bit different and represents different threat levels and response strategies/tactics. The six types of gas emergencies we’ll discuss in this article include the following:

Excavation damage (main or service line).
Outside odor of gas (underground leak).
Inside odor of gas (minor or major leak).
Building explosion.
Ignited leak.
Locked building containing gas.

This list is not comprehensive, as other types of leaks, such as transmission lines, are beyond the scope of this article.

Getting Started

To start, get your gas provider’s response procedures. Your fire department’s SOPs should generally mirror the gas provider’s with obvious exceptions such as closing street valves, bore holing, and leak fixing.

Our mission is life safety first. If your gas supplier will not share its procedures, it’s important to remember that in most states these procedures are covered underthe Freedom of Information Act and, as such, they are public documents. You need this information as a starting point.

Another source of gas industry best practices is from Gas Filled Occupancies— Emergency Response Protecting Employees, First Responders and the Public Observations and Analysis of Natural Gas Explosions, a 2022 white paper from the American Gas Association. It contains several model SOPs for you to consider.

Many fire departments across the United States spend too much time waiting for the gas technician to respond to the emergency. If this includes your department, you may be operating without the gas technician for an extended period of time. The overall risk of the incident may change as the timeline evolves. Case studies have shown devastating gas explosions have occurred 40 or more minutes after a fire department’s arrival on the scene. Your SOP must provide a plan for operations for this time. Look back at your gas calls and pick an average length of time for which you operate. Cover this in your SOP in the context of first-due units, additional alarms, mutual aid, support for operating units, and a policy to turn the call over to the gas technician.

Policies for Responding Units

Each SOP should contain a policy section. You want your first-due officers to be aggressive and use their expertise and experience to size up and direct the operation. SOPs must balance giving first-in officers latitude to make decisions and assignments while simultaneously providing clear guidance for size-up as well as strategic and tactical actions. Policies give fire officers and members some rules by which to conduct their operation. Policies set the parameters for their work. Essentially, policies give them the rules to play by.

Examples of Policies (General and Specific)

Life safety of members and civilians is our mission in explosive gas emergencies.
Kill box (blast zone): One to two houses, or 150 feet in all directions from the reported leak or hazard. The Emergency Response Guidebook recommends 300 feet in all directions. (This may be impractical in densely populated areas.)
Park apparatus one to two houses or 150 to 300 feet from the reported incident location.
Send one firefighter and one officer with each gas meter to predetermined locations in the occupancy to Command, or as directed.
Shutting off the gas at the meter is always an option as directed by the IC. However, only the utility company should operate valves in the street and those that service other parts of the distribution system.
Major/minor gas emergencies: Assume major until detection and monitoring prove otherwise.
In major emergencies, life safety is or may be compromised.
Establish the incident command post outside the kill box.
In major emergencies, contact emergency medical services (EMS) for standby, appoint a situation unit leader to document readings, and appoint a safety officer.
Only force entry into locked buildings/apartments after you’re sure a confirmed or highly likely life hazard is inside or if air monitoring and size-up determine a manageable risk.
Consider action levels. Any level/odor/condition situationally concerning is grounds for tactical withdrawal.
Direct civilians to evacuate the occupancy as soon as it’s practical to do so.
10% LEL: Mandatory evacuation of civilians if you have not already taken them out.
20% LEL: Mandatory evacuation of fire department members seems a reasonable level.
Do not operate any electrical switches or introduce ignition sources.
The department training officer will ensure officers and members train on this SOP at least annually.

Strategy and Tactics

Your SOP must contain both strategic goals for the IC and tactical tasks for members to accomplish the IC’s goals. The checklists that follow can be part of your SOP. They assume the officer or member has a thorough understanding and is well trained in the entire gas response SOP. They also assume the officer or member is up to date on any necessary background information. These items are based on gas industry best practices and represent a summary of key points from policy, procedures, strategy, and tactics within the full SOP. Let’s use an “outside odor of gas” reported at 3 Main Street as an example.

Strategic Goals for the IC

Establish an incident command post.
Ensure the gas utility has been requested.
Begin size-up: Interview the caller/ occupants and evacuees and consider all potential leak sources (inside, outside, underground).
Estimate the kill box.
Evacuate based on size-up.
Determine if gas is migrating underground into nearby buildings.

Tactical Actions for the First-Due Units

Check buildings (the main door and the point of entry) and subsurface structures closest to the leak source first.
Evacuate as necessary.
Check buildings on all four sides of the odor site using inside gas leak procedures.
Check subsurface structures and buildings on all sides of the leak site until readings are 0% LEL.
Open manholes to vent gas if readings exceed 25% LEL in manholes. Note: Check with your local gas supplier and do not open underground electric manholes.

The purpose of these actions is to rule out the possibility of a gas main or service line leaking underground with gas migrating into the building and accumulating there. The outside team from the ladder company will go to the gas meter location that may be in the basement, utility room, or mechanical room. The purpose of this assignment is to assess the possibility of leaking gas from high- pressure mains or service lines (a gas pipe from the main to the building) that may be migrating through the soil or along/through pipe chases, sewer pipes, conduits, or simply cracks in the foundation walls. Utilities call this area the point of entry. It is always a good place to monitor as part of your size-up.

The engine company will respond to the reported location of the odor/leak or complainant to gather size-up information. The overall purpose of these assignments is to determine and rule out a major, life-threatening leak.

Assigning a member or team to go to the gas meter provides two important size-up and mitigation actions for the IC. First, the member can shut off the gas if the leak is significant and above the meter in piping running through the building. Second, if the meter indicates gas flowing into the building, it provides the IC with important size-up information from which to build a strategy.

Additional Points to Consider

The FDNY SOP for gas leaks makes the following key points that may be useful to add to your SOP. “Most natural gas emergencies are resolved through investigation and simple mitigation. On occasion, a response can elevate to a major gas emergency, at which point FDNY strategy should focus on securing life safety (evacuation). The following conditions are indicative of a major gas emergency and may require changing from a simple mitigation strategy to one that emphasizes all efforts on securing life safety (including utility personnel and first responders).’¹

Indications of a major emergency include the following:

Damage to gas mains, service lines, or meters.
10% LEL detected outside.
20% LEL in subsurface structures (manhole or storm sewer).
Gas present in two or more sewers.
Indications of gas migrating into buildings from an outside source.
Gas leaking into a structure that cannot be shut off.
Gas inside a wall or building void.

The FDNY SOP also covers some specific tactical assignments worth considering, including the following:

“If any natural gas levels are displayed on the natural gas meter upon entering the building, or while proceeding to the reported location within the building, the inside team should proceed directly to the basement/cellar to evaluate conditions.”

Clearly, a spinning half-foot dial does not mean all the gas is leaking, as some gas may be used in properly functioning appliances (photo 2). Recently, my fire department responded to a dispatch report where the occupant broke the gas pipe while moving the stove. The member assigned to the meter recognized the half-foot dial spinning, indicating gas was flowing, and notified Command. Command ordered the meter shut off, thereby reducing some of the danger for both civilians and our members (photos 3 & 4).

2. Note the half-foot dial. If it is spinning, gas is flowing past the meter into the building. *(Photos by author unless otherwise noted.)*

3. A crescent wrench or halligan can shut off the quarter-turn gas valve.

4. Rotary meters are used for large occupancies. A spinning black and white disk indicates gas flowing into the building.

5. Explosive gas detectors, from left: metal oxide based flammable gas sensor, fourgas and metal oxide detector, and remote sensor with laser technology.

Locked Building

Many utilities request the fire department to force doors on buildings or apartments that contain natural gas or liquefied petroleum gas. Check your local utility’s procedures. Many gas utilities’ procedures specify that any reading of gas going from the inside to the outside is cause for tactical withdrawal. At that point, remotely shut down the gas and electricity (to limit ignition sources) and wait for the building to vent down.

You can identify this condition by placing your explosive gas detector near a door or windows or possibly by inserting the probe around flexible door or window seals (photo 5). Since you do not know the amount of trapped gas inside the building, the venting process may take several hours to reach safe levels. The utility company procedure to withdraw when any level of gas is detected inside a locked building seems extreme. Recall that we do not know the level in other areas; there is no life hazard; the building contains an explosive gas, oxygen; and ignition sources make it a bomb—a big, unpredictable bomb.

Typical fire department venting procedures are not recommended because you will have to put members’ lives in danger while working in and around the building. Check with your local utility to confirm that the best procedure is to remotely shut down the gas and electric service (to minimize ignition sources and cut off the flow of gas) and wait for the building to naturally vent down to safe explosive gas levels. Depending on the porosity or energy efficiency of the building, this may take several hours.

As firefighters, we are programmed to fix everything right now. Waiting goes against our instinct. Consider gas emergencies as a hazmat call as opposed to a fire/smoke condition. If your gas company recommends remotely shutting off gas and electricity and waiting for the gas levels in the building to reach safe levels, it may make sense for you to include this in your SOP. (Remember: Emergency generators may start up when utility electric is shut down.)

Consider these two important facts when writing your SOP for locked buildings:

Civilian and firefighter life safety is our mission. A locked building with gas leaking inside presents a high risk of an explosion. It contains all the parts of a (big) bomb. Natural gas is not toxic, but it cancause asphyxiation due to oxygen displacement. Our firefighter training and fire-centric brains tell us we need to force entry, search, and rescue civilians. Have you ever heard of anyone asphyxiated by natural gas? It’s incredibly rare. (Examples include instances where a utility worker jumps into an excavation where large volumes of gas are escaping and confined spaces such as manholes and manure pits.)
Civilians are not asphyxiated by natural gas. We have two reasons for this: First, the odorant in natural gas (ethyl mercaptan) can be detected at about one part per million (ppm). One ppm is the equivalent of ki6 inch to one mile (one million ppm). According to the Centers for Disease Control and Prevention, levels of three to four ppm of the odorant make people nauseous and they self-evacuate. Many urban departments routinely force doors in occupancies that contain gas. This seems acceptable due to the early detection that results from the low odor threshold for healthy humans. An apartment with a gas leak will be readily detected by other apartment dwellers nearby. In a suburban or rural situation where residential buildings may be separated by significant distances or for locked commercial urban buildings, explosive levels of gas may accumulate undetected over time prior to the fire department’s arrival. Carefully consider the life safety risk to members in the name of a very likely unnecessary and dangerous search. We would not force the door and rush in for a toxic hazmat. So why would we do it for an explosive hazmat?

We don’t want to depend on detecting any odor with our senses. Soil conditions can scrub out the odorant. Good, thorough air monitoring is the standard for determining confirmation or denial of a hazardous situation.

Explosive Trends

Gas Filled Occupancies—Emergency Response Protecting Employees, First Responders and the Public Observations and Analysis of Natural Gas Explosions contains fireground data we can use to fine-tune our SOPs. The purpose of this document is “to provide guidance to natural gas utilities on practices that may supplement current practices related to the accumulation of natural gas.” This paper was based on examination of 50 fatal gas incidents across the United States, which caused 78 fatalities and 168 injuries from January 2010 to December 2020.¹

Data from these incidents show trends that we can use to formulate reality-based, experience-based, and executable policies, procedures, strategies, and tactics in our SOPs. Most of the known fatalities to utility and fire department personnel and a majority of the injuries occur within 50 feet of the building. Several of the fire department LODDs were near the building that had already been evacuated. Risk-based response must be a critical element of our size-up and decision-making process. Responders must respect and act intelligently to the explosive potential of trapped natural gas and propane.

According to the AGA study, the majority of fatalities occur within 100 feet of the building. In the study, 59 of the 78 fatalities were inside the building when it exploded. Based on these 50 documented explosions, injuries to individuals located 100 to 200 feet from the building were minor (not life-threatening and nondisabling). Again, this is the kill box, which is the area where firefighters are likely to be killed if the explosive gas ignites.

Using this data, we can provide practical standoff distances for response to explosive gases. Unbelievably, many fire departments place their first-due units too near or in front of the address reporting the gas leak. Our good luck reinforces our bad habits, which is why we get away with this ridiculous action. We all go to many minor gas leaks, which can contribute to our naturally developing complacency. Don’t park in front of the bomb.

Help with Coordination

One of the best ways to maximize training and coordinate on-scene actions with your local gas utility is through the U.S. Department of Transportation—Pipeline and Hazardous Materials Safety Administration Pipeline (PHMSA) Pipeline Emergency Response Initiative (PERI) program. This program links local fire departments with local gas suppliers to provide training and develop collaborative relationships. In essence, the utilities supply funding and technical assistance so state or local fire training centers can provide high-quality training for response to explosive gas emergencies.

Beginning in 2012, PHMSA collaborated with pipeline operators and emergency responders to build this public-private partnership. PERI bridges that gap and fosters engagement, training, and information sharing among the diverse stakeholders involved in pipeline safety and emergency response.

Since 2015, PHMSA has facilitated PERI outreach to all 50 states and will continue to encourage collaborative engagement as a model for safe, effective response to pipeline emergencies. Several states have developed PERI-like programs that serve their broader community well and have exemplified successful collaboration. The PHMSA’s Community Liaison Services has taken a leadership role in helping states initiate PERI in your state and nationwide.

The U.S. Department of Transportation’s Emergency Response Guidebook (ERG) recommends a 330-foot isolation zone in all directions for releases of flammable gases (see Guide 115, “Flammable Gases“).² In urban and suburban fire departments, this distance is often not practical due to limited first response resources and the population density of these areas. Consider the data from the above report and include in your SOP a safe and practical distance to ensure the safety of responding units.

Of course, you will take manageable risks during size-up and incident mitigation operations. Your decision on the kill box size in your SOP is like your decision on your action level for meter readings. There are no national standards. Your four-gas monitor alarms at 10% LEL because that is the confined space standard. The ERG is a wonderful reference, but what good is it to have the ERG recommendation in your SOP if your officers and members don’t—or can’t—execute it?

Another recommendation from the AGA paper was collaboration between the gas company and local fire departments. The U.S. Department of Transportation-Pipeline and Hazardous Materials Safety Administration (PHMSA) and several state regulatory agencies have adopted the Pipeline Emergency Response Initiative (PERI) to facilitate this collaborative process.³ Several states, including Georgia, have excellent cooperative programs that effectively provide high quality firefighter training funded by utilities and planned and delivered by firefighters.

Gas leaks are a common alarm for most departments, and it is easy to get complacent. It is critically important for fire officers to provide effective policies, procedures, strategies, and tactics in your SOPs to ensure safe and effective responses to meet our mission of life safety.

ENDNOTES

Gas Filled Occupanaes—Emergency Response Protecting Employees, First Responders and the Public Observations and Analysis of Natural Gas Explosions. American Gas Association. 2022, bit.ly/3XNC3PA.
Emergency Response Guidebook (ERG). Pipeline and Hazardous Materials Safety Administration, U.S. Department of Transportation, bit.ly/4gIy4Mz.
“Pipeline Emergency Responders Initiative (PERI) Overview.” Pipeline and Hazardous Materials Safety Administration, U.S. Department of Transportation, bit.ly/3XvNYCl.

REFERENCES

“Chapter 35: Flammable Gases.” Official Website of the City of New York, FDNY Downloads, International Code Council, 2012, bit.ly/47Y7GdX.

Community Liaison Services. Pipeline and Hazardous Materials Safety Administration, 2019, bit.ly/4gaimtt.

Noll, Gregoy. Pipeline Emergencies. 3rd ed., Hildebrand, 2018, bit.ly/3ThneDm.

Prothro, James. “Pipeline Safety and Response Considerations: A Collaborative Approach.” Fire Engineering, September 2023, bit.ly/4ds7GUh.

JERRY KNAPP is the chief of the Rockland County (NY) Hazmat Team, has a degree in fire protection, is a 48-year veteran firefighter/ emergency medical technician (EMT) with the West Haverstraw (NY) Fire Department, and is a former paramedic. He served on the technical panel for the UL residential fire attack study. Knapp is the coauthor of two Fire Engineering books: House Fires and Tactical Response to Explosive Gas Emergencies. He is a contributor to Fire Engineering and several state, national, and international fire service trade journals. He is also the author of the “Fire Attack” chapter in Fire Engineering’s Handbook for Firefighter I and II. He retired from the U.S. Military Academy, West Point, where he served as the plans and operations specialist at the Directorate of Emergency Services.