Jason Krusen: Smells, Bells, and Spills


Fire departments commonly answer three types of hazardous materials-related calls on an almost daily basis. These calls may vary based on geography and time of year, but we are bound to respond to them sooner than later. These calls are for the smell of gas (natural gas and propane), carbon monoxide alarms, and fuel spills (gasoline and diesel/kerosene). They are the most basic of hazardous materials calls and, for the most part, are handled by a suppression unit with a one- or two-unit response. Depending on the structure of the department or response plans, this may be all that is available and, quite frankly, all that is needed.

In the more suburban and rural areas of the country, hazardous materials response teams are commonly county or regional in nature and cannot provide a timely response to one of these calls. In the more urban and densely populated areas with significant industry, a hazardous materials unit may be a likely resource.  Nonetheless, understanding how to respond safely and efficiently to these three calls is important.


Response to an odor of gas or a report of a cut gas line is an everyday occurrence for many departments and for the most part an uneventful call. It is one that often results in units standing by at the leak until the gas company arrives to mitigate the incident, yet every month there are significant events involving a gas explosion somewhere in the country. Fire departments continue to respond to these calls with a strong sense of complacency, which is reinforced every time the call is handled luckily without incident. Often, the basics such as placing a line on the ground or establishing a water supply are overlooked.

These calls can originate in several ways. Typically, a complainant discovers an odor of gas and is alarmed, rightfully so, and calls 911. Occasionally, the individual may contact the service provider, especially if service such as repair work or delivery of product was recently rendered.    In other cases, the person may have seen the event take place, such as a buried gas line being cut during a digging operation, or may hear a gas leak from behind an appliance. This usually initiates a response most often from the fire department and other local responders depending on local response plans.

While responding, it is important to ensure all occupants are out of the structure if the leak is reported to be inside a structure. When the leak is outside, all workers, residents, and bystanders should stand back a safe distance from the leak depending on the product. Knowing what is in your community will help, but you can never assume until you are on scene, so always plan for the worst. If possible, you can include a few simple questions in the standard operating procedures for dispatchers. If you cannot do that, the responding personnel can prompt the dispatchers to ensure that the right questions have been asked of the caller.

As the first unit arrives on scene, the approach should be from a safe distance until the location of the leak source location is identified.  Rushing in can create a problem and possibly an ignition source. One unit commits to the street while all others stage until the location is positively identified. If possible, units should approach from opposite directions, providing the best opportunity to position from a safe location.  All personal protective equipment should be donned in preparation for the worst. An ignition source will present itself unannounced, many times catching the responders by surprise.  Do not commit additional resources until the source is identified.  Gas can easily move underground in natural cracks, fissures, and voids around pipes

The sources of the odor are natural gas, liquefied petroleum gas (LPG), and sometimes gasoline. When dispatched to a smell of gas or a report of a gas leak, it is very important to prompt the dispatcher for additional information. Although these three sources all produce a smell of “gas,” they have individual characteristics that will affect how they move and may be mitigated.  The general public doesn’t think to differentiate. Because of these differences, responders should have different safety concerns.

The suspected area of the leak is also important.  A leak inside of a residence allows for a concentration of vapors that is unaffected by the natural tendencies of the characteristics that a particular product may have. This can minimize the window of opportunity to act before the product reaches a flammable range. So, any additional information can assist in determining to product before units arrive on scene.

When addressing gas leaks, always prepare for the worst and implement all safety procedures.  A gas leak should never be underestimated, as it is always changing, especially if the leak is still active. A damaged line can leak vapor for hours without incident; however, a change in the climate, the introduction of an ignition source, or the accumulation of enough product to reach a flammable range can cause the incident to suddenly change. This was the case recently in Columbia, South Carolina, when during the repair of a ruptured gas line, a fire ball quickly lit off without warning.  Luckily, the fire department was in place and prepared for the worst.  Two hoselines were in place, as were firefighters dressed in full PPE with an established water supply. They quickly provided a water curtain so gas workers could safely escape from harm’s way.

The fire department received the alarm around 16:30 hours and arrived on scene to find a contractor performing a boring operation under a busy downtown intersection at the end of the business day. The machine performing the boring was several feet away from the suspected leak at the corner of the intersection, but because this was a boring operation, there was no hole in the earth at the point of the leak. The machine penetrated a gas line several feet below street level, which is a somewhat common occurrence. Crews were on scene for nearly two hours. This gave responders plenty of time to drop their guard before the gas leak caught fire. This was not the case, however; the crews remained vigilant and ready.  

Up to that point, the Columbia Fire Department had not experienced a gas line erupting in flames while crews were actively working, but because a standard operating guideline was in place and followed, the incident was handled properly.  In addition to the guideline, the department has a good working relationship with the gas company; they respond jointly to these types of calls on an almost daily basis. The department also trains on how to address these calls properly because of their frequency.

Natural gas (methane) leaks can occur inside or outside of a structure. Those outside are not nearly as dangerous, since natural gas is lighter than air and wants to rise in the atmosphere.  The immediate area around the leak is a concern, but unless weather conditions are controlling the movement of gas, it is going up. Ignition is still a concern as learned in the incident previously mentioned; however, a natural gas leak inside a structure is more dangerous than one on the exterior.  

It is critical to the safety of personnel that responders do not work beyond their level of training. It is not uncommon to arrive on the scene of a cut gas line to find that a worker or homeowner has bent over a poly gas line and taped it off in an attempt to stop the leak. This technique only slows the release and is not recommended. What most people do not understand is that a great deal of static electricity is created by performing this function. Once the charge is built up, there is a good chance of a discharge that will result in an ignition source.   

A natural gas leak inside a structure presents issues that are not encountered in an outside release. There is a ceiling involved, restricting the flow of gas, essentially trapping it “in a box.”  The flammable range now has more of an opportunity to be reached. The sudden and destructive ignition of natural gas is more than enough to move a structure off its foundation, if it doesn’t flatten it, depending on the concentration of gas at the time of ignition. In addition, anyone in or nearby the structure can be injured by the ignition and ensuing fire ball or debris moving rapidly from the blast site.

When handling a gas leak inside a structure, you must consider the ventilation process once the leak is stopped. If the environment is too rich during the leak, the vapors will not ignite; but as the structure is ventilated, the concentration of gas passes back through its flammable range, 4 percent-15percent concentration in air. There have been incidents where fire departments were on the scene ventilating a structure at the time it ignited. Atmospheric monitoring will help prevent this by informing the responders of the actual levels.

Using the correct meters will also assist in properly identifying the leak source. Many responders make the mistake of using only a multigas meter. These meters, while extremely useful in identifying if the overall atmosphere is safe, are not useful in pinpointing the source of the leak. If this capability is called for by your unit or department, a meter with a metal oxide sensor will be able to detect the source. This is not to say the multigas meter should be disregarded; use it with a complementing metal oxide-equipped meter. These two meters will help ensure the safety of the responders on scene.

LPG (Propane)

LPG (propane) presents a different set of concerns, and a leak is just as dangerous outside as it is inside.  Because LPG is heavier than air, its footprint grows as the incident progresses, exponentially increasing the risk of ignition. The gas will seek low-lying areas downhill of the leak such as drainage ditches. Inside a structure, the pilot lights of a water heater or oven will quickly offer an ignition source. The flammable range for propane is 2 percent-10 percent concentration in air, slightly lower than that for natural gas. Because of the differences, it is important for those operating the meters to understand where to monitor (high or low).


Gasoline is a third type of gas leak that may trigger a response. For this article, the vapors of gasoline are being addressed, not a liquid leak. Although not as frequent as natural gas calls, it is not uncommon to respond to a report of an odor of gas and to arrive at a residence to learn gasoline-powered equipment is stored under the house in a crawl space. The vapor will eventually permeate into the structure if the container leaks or is left open. In most cases, it is merely an odor and nowhere near dangerous levels, although it has the potential to become a problem. As mopeds gain popularity in urban areas and on college campuses, it is common to park them on the balcony or even in an apartment in fear of their being stolen. This presents a whole other problem should there be a fire in the structure.  

If a natural gas or an LPG leak ignites, do not extinguish the fire until the leak has stopped.  Although this may seem counterproductive to what we do, it is the safest approach. Once the leak has ignited, it cannot ignite again, but snuffing the flames before the leak is controlled may allow for a larger buildup of the product before it finds another ignition source. The best thing to do is to protect exposures from flame impingement.

Network with the local gas companies in your response area and ensure everyone is operating under the same plan. The gas companies can provide valuable training to responders about the dangers of the product and what resources are available to assist in a leak or an emergency.  Knowing about those resources ahead of time can make a great difference at the time of the emergency. Even better than knowing about the resource is getting to know the personnel who are likely to respond. Being able to get set up to support the mitigation process prior to the gas company’s arrival will assist them in correcting the issue, thus getting responders back in service more quickly. This also helps strengthen the relationship between the fire department and the gas company.

Good customer service is also important when operating on the scene of a gas leak, especially in colder months or when gas service is required for heat.  Many responders are quick to isolate a gas meter before conducting an investigation as to the source of the problem. Once isolated, a gas meter should never be turned on by a responder. This should be left up to the gas company to ensure all appliances and pilots are relit properly. By taking a moment to look into the problem, sometimes an individual appliance can be isolated, thus leaving gas to the structure to power other appliances.  Consult with your local gas provider to see what it prefers and with your department’s guidelines.   

Training personnel on the dangers associated with gas leaks and developing operating guidelines will provide a safer scene for responders. Remember to gain as much information as possible while en route to the call, including product information and occupant locations. Once on scene, use atmospheric monitoring to ensure a safe environment while operating on the scene. Do not work beyond your level of training, and treat every leak as if it were going to ignite.


JASON KRUSEN is the special operations chief for the Columbia (SC) Fire Department (SC). He has more than 20 years in the fire service.  He is also a planning manager for SC-TF1, as well as the team coordinator for the department’s Regional Collapse Search & Rescue Team and the Weapons of Mass Destruction Haz-Mat Team. He is the president of the Fire Smoke Coalition and an instructor for E-Med Training Services, LLC.


No posts to display