Basement fires: Building safety margins to reduce the impact of error
The solution to creating a safety margin is understanding the dragons we face and learning the lessons to be more proficient and go home safely
FireRescue1’s webinar, "Basement Fires: Tactical options for the threat below,” presented by Battalion Chief Jake Barnes and Captain Gil Pedroza, details how to identify a basement fire, the different types of basement fires, the impact of building construction and fire dynamics, plus fire attack options. View the on-demand webinar here.
On April 25, 2008, Captain Robin Broxterman and Firefighter Brian Schira lost their lives fighting a basement fire in Colerain Township, Ohio. Broxterman and Schira responded to a 911 call for a fire alarm at a suburban address. Upon arrival, they made entry to the front of the home and located a fire in the basement. They stretched their attack line into the basement and were subsequently trapped and killed by a collapse of the main floor and heavy fire. Later-arriving crews located a rear walk-out basement door during a 360 that would have allowed better access to the fire.
Since that day, we have learned more about the modern fire environment, the impact of the synthetic materials present in the home today and their impact on fuel load. We have measured the differences in burn times of lightweight building materials. We have watched UL’s Fire Safety Research Institute (FSRI) and NIST engineers show us how flow paths develop, how they can burn us, and how to predict hostile fire events. While some of these factors can be present on any fire we respond to, a basement or below-grade fire will likely check all the boxes, and that’s why they continue to be so dangerous.
Synthetic furnishings and building materials burn hotter and faster and fuel the smoke. The hotter temperatures will cause the smoke and air near the fire to become even more buoyant than usual, developing pressure and moving that atmosphere up and away from the seat of the fire. This leads to the formation of flow paths and causes firefighters to be caught under exhaust paths while accessing the fires.
The construction of the home can also play a role. I was part of the response to a house fire where crews found high heat and smoke but no visible fire upon arrival. Crews quickly searched the main and upper floors of the building but could not locate the heat source. Upon exiting and performing another 360 with a thermal imager, they noticed the tell-tale heat signatures of a balloon-frame house. A well-established basement fire had worked its way up the wall spaces. Crews accessed the basement and ultimately extinguished the fire with a cellar nozzle. By the time the fire was controlled, floor collapse had begun to occur on one portion of the main floor.
The increased heat and speed of the flow path will burn through lightweight structural members faster than it did with cooler fires and larger-dimension lumber. This leads to faster fire spread and earlier structural collapse.
FSRI performed burn tests to determine collapse times of various types of floor assemblies and how they behave under real-world conditions. One of the most important findings from the report, titled Improving Fire Safety by Understanding the Fire Performance of Engineered Floor Systems and Providing the Fire Service With Information for Tactical Decision Making, was that even the lumber used in modern construction has changed. In this test, a floor assembly constructed of newly purchased 2” x 10” lumber failed in 7:04 minutes, with no prior indication of burn through before failure. Compare this to a floor assembly made from legacy 2” x 8” lumber removed from an older home for the test. The older floor, with smaller dimension lumber, lasted 18:05 minutes before collapsing. The legacy floor also showed signs of burn through a full 2 minutes before collapse.
Lastly, modern homes are built with energy efficiency in mind. This can make it harder to locate a fire from the exterior. This means fires can burn longer undetected and become ventilation-limited. Once we arrive and introduce oxygen to the fire environment, we can unintentionally create a hostile fire environment in short order.
The Cherry Road townhouse fire in Washington, D.C., on May 30, 1999, was just such a fire. The arriving crews worked in a stairwell to access a below-grade fire. Unbeknownst to the interior crews, they had created an exhaust for fire and were exposed to extreme conditions in that flow path. The fire claimed the lives of two D.C. firefighters.
Put this all together, and you can see why basement fires are so dangerous. They chew up our safety margins and punish us for small mistakes.
Basement fire solutions
The good news: While basement fires do check all the hazard boxes, we already have the tools to build the safety margin we need to operate in this dangerous environment. What can hurt us in a basement fire can hurt us in any fire. Rather than training specifically for basement fires, let's become more proficient in fire suppression in general. This will help us when faced with a risky fire, no matter where it is.
FSRI classes: FSRI uses science to quantify our fire environment, how that environment has changed, and exactly how our suppression techniques work. These classes are free and provide the training we need to understand our environment. Check out https://training.fsri.org and learn the lessons to build yourself some safety margin.
360 size-ups: As we have seen, basement fires can be a fatal place to work. Too many times, a crew committed to entering the basement through a stairwell and ended up in the exhaust portion of the flow path. In some of these cases, an alternate access method existed and would have allowed the crew to attack the fire on its level. Take the time to perform a 360, and do your best to locate the fire, and imagine all the methods to attack it, including flowing water into building openings from the exterior of the building before going inside.
Nothing showing means nothing: We have heard this phrase multiple times, but it's doubly true for a below-grade fire. The fire may not have ready access to a building opening, or maybe vent-limited. These can both mean we can inadvertently find ourselves in a flow path if we make the wrong decision. Be skeptical of the fire call with nothing showing, and take the time to determine what you have, where it is and where it might be going.
TICs spot the heat: A thermal imaging camera can be an essential tool for sizing-up a below-grade fire. We can look for heat signatures in windows to determine locations of heat. We can see evidence of balloon-frame construction using a TIC to image the exterior of a structure. We can see evidence of a flow path and try to determine neutral planes. Like everything, however, we need to take the time to look and understand what we are seeing. Slowing down and taking a second can be the difference between recognizing a bad situation or missing the signs.
Flow paths: When we are working on a fire, any time we open the building, we need to evaluate what happens to the smoke. Does it clear entirely? Does it fill with smoke and heat? What is the rate of change of the smoke? Is there a neutral plane? These are critical questions to ask and understand before deciding to access a fire from above. FSRI has online resources, and you can also check out the SLICE-RS program for more training on the topic.
If the opening is an exhaust, it means you risk working in untenable heat, plus there is an intake somewhere else. Committing to working in a flow path is a high-risk maneuver and one that should not be undertaken without serious consideration.
We can often flow water and use the reach of our hose stream to change the environment or hit the fire. If you can, use this to your advantage to control the basement environment before moving into it. Once you are there, rapidly apply water from a distance to reset the fire and prevent it from burning unchecked and weakening the structure of the building.
The FSRI basement fire program also shows the effectiveness of flowing water through a hole cut into the floor to cool a basement space. This can have the secondary effect of cooling floor structure to provide a greater margin of safety before a collapse can occur.
Basement fire training
I have been through numerous training evolutions where the goal was to train firefighters to quickly move down the stairs to "get under the heat." This was a solid tactic in legacy structures with long-burning building materials and natural furnishings.
The problem now is if the stairwell in a modern structure becomes an exhaust flow path, “getting under the heat” isn’t going to work. The turbulent, hot smoke in that exhaust can radiate so much heat that it will overcome our turnout gear. In the Cherry Road incident in Washington, D.C., estimates of the heat flux from the flow path in the stairwell were around 80 MW. This level of heat flux, or the measure of how much heat is transferring to your turnout gear, is not survivable.
Bottom line: We need to teach new firefighters to recognize flow paths and look to cool from a distance, not just program them to rapidly move into stairwells without fully understanding the risk they are taking.
We must be at our best
Basement fires can be looked at as high-risk/low-frequency events that offer us little in the way of safety margin. We need to be at our best when we respond to one, as any mistake can have negative consequences. We can’t keep doing things the same way, especially on a kind of fire that will make us pay for being sloppy with our choices. The solution to creating a safety margin is understanding the dragons we face and learning the lessons to be more proficient and go home safely.