Last winter, I took a few minutes to travel around my response district and took an assessment of many potential hazards to my company. I was surprised to find that more than three-fourths of the dwellings in my district were still heavily loaded with heavy wet snow.
When we arrive at a reported building fire, the dwelling’s snow load should be directly considered when the incident commander determines a strategic plan. The potential of a roof collapse before the fire is put out should be a consideration as well. The structural support system holding all that snow may be directly or indirectly under attack by the fire, and that can add to the potential early onset building collapse.
Another consideration should focus on newer dwellings constructed with a lightweight “truss-roof” system. As seen in many past fire tests, a lightweight truss roof system, once assaulted by fire, fails at an alarming rate. None of those fire tests were ever conducted with a potential snow load as seen from our recent storm of the week.
|The dwelling’s snow load should be directly considered when the incident commander determines a strategic plan. (Photo by Willie Cirone.)|
Heat loss from a building may result in some snow loss through melting between storm events. Roofs that allow heat loss to melt snow are called “warm” roofs; this may be by design or lack of proper insulation. Other roof systems remove lost heat before it has a chance to melt the snow. These roofs that prevent heat from reaching the snow are known as “cold” roofs. Sometimes buildings are either unheated during winter months or are intentionally kept at or below freezing so there is no heat loss that results in snow melt or ice buildup.
One factor that needs to be considered by incident command is how the department can safely commit to an interior firefight while considering the level of danger. What are the dangers to be considered? Well, it is not as easy as what you see from the street. Understanding building construction has never been more important when you add in snow loads. Do you expect normal tasks like fire suppression and search/rescue to be done quickly when firefighters encounter delayed ventilation? Interior companies will certainly encounter an underventilated fire condition. Interior conditions will not be the same as operating during the spring, summer, or fall months in the Northeast.
Ladder companies will certainly have a delay in providing vertical ventilation because of lack of access to the roof, large snow banks that limit truck access, carrying a ground ladder in deep snow (difficult at best), and access to the physical roof that may be buried under 18 to 36 inches of heavy wet snow and ice. Adding firefighters to a potentially overloaded roof can trigger a roof collapse as well, not to mention the lack of solid footing and the ability to sound the roof before stepping off – and not too often do we ask the truck company to bring a snow shovel with them to just find the roof’s surface! Attempting to stay on the aerial to get the job done safely? Well, good luck trying to shovel from there. These delays can definitely change the interior company’s thermal exposure to extreme heat buildup and underventilated fire dynamics.
Every firefighter on the fireground, from the chief to the probationary firefighter, needs to stay alert for signs of overhead hazards during winter month operations. There typically has been a lot of focus on building collapse potential with snow loads, but staying cognizant to potential heavy snow or ice slides that could cause serious personal injury or death to responders is a reality as well. This type of overhead assessment must be done on arrival by the first-due company officer and be continually monitored throughout incident by the incident commander.
|We need to stay alert for any signs of a structure weakened by fire, prefire snow loading, or poor general maintenance. (Photo by Willie Cirone.)|
For you incident commanders, this is an excellent point to add to your safety officer’s “exterior checklist.” We also need to stay alert for any signs of a structure weakened by fire, prefire snow loading, or poor general maintenance by listening for strange noises of the building settling under the unusual loads that occur during a fire operation, noting any visual signs of sagging roofs or eaves, leaning, bowing, separating wall connections, interior wall board cracking, or water seeping from above; these are all positive signs or indicators of a potential impending collapse.
If you choose to go interior and aggressively mitigate from underneath, which we often do in the United States, I highly recommend using my expanded “command team” approach to managing an incident by assigning an interior safety officer to assess these specific hazards. As we all know, our initial interior companies are many times taxed beyond their span of control (thinking) and may miss some of these potentially lifesaving signs of danger ahead.
Bottom line: The fire service should use a strong risk vs. gain decision-making model for lightweight or weakened dwellings and choose the appropriate tactical model to get the job done as safely as we can!
Take care, and go interior if conditions allow.