Author's note: Immediately after 9/11, I created a tactical concept in high-rise firefighting called a Rapid Ascent Team. Initially, it was based on the obvious physical and tactical strain on firefighters having to rapidly ascend to upper floors of tall buildings to effect rescues...
To access the remainder of this piece of premium content, you must be registered with Firehouse. Already have an account? Login
Register in seconds by connecting with your preferred Social Network.
Complete the registration form.
Other gases from burning natural materials and synthetic compounds, such as hydrogen cyanide, hydrogen chloride and vinyl chloride, can add to the deadly threat of exposure to fleeing occupants. The two predominant gases that kill most people are CO and hydrogen cyanide. Most civilians do not understand that the exit stairs are typically a safe area of refuge — until the fire attack commences. Then their path of egress can become a bad location for them to be if they are in the stair above the fire where a hoseline is being advanced onto the fire floor. (An exception would be a hot-weather fire with a significant "reverse stack effect," or downdraft, taking place, whereby air and smoke are pulled downward via shaftways.) The door must be propped open during this procedure to prevent it from closing on the hose. Without good stair pressurization keeping the bulk of toxic gases from entering the shaft, contamination is likely to occur. Attaching the attack and backup lines out on the fire floor to prevent this from occurring is not a safe, viable option.
I recently added one more key duty to the Rapid Ascent Team assignment and that is an extremely important concern for every competent fireground commander in a high-rise fire — knowing where the major concentrations or pockets of CO reside within the tower. Contrary to popular opinion, CO is only slightly lighter than air. In its purest form, it is only 3% lighter than air. Still, except in cases of "reverse stack effect," CO rises in stairwells, elevators and other shafts, which has resulted in multiple-fatality incidents remote from the fire area. Why does this occur? Simply, it is the heat convection from the fire in combination with the natural stack effect of the building itself that brings this about. Early into the fire, the vast majority of SOPs dictate that a range of three (minimum) to five (maximum) floors of "stair runs" above the fire must be searched for occupants who are evacuating down the attack stair. In addition, many big-city SOPs also mention that the upper floors at and around roof level in this stair must be checked for smoke migration and contamination early into the fire. Is this truly adequate?
Certainly, it can be argued that wherever the visible/particulate smoke is, the non-visible CO has to be in close proximity. However, in many circumstances, the CO never makes it to the top of the building, but instead will stratify in one or more pockets between the fire floor and the roof (and sometimes even below the fire floor in warm-weather fires). These pockets must be sought out, identified and reported back to the command post for tracking purposes, not unlike the tracking of fire crew locations and assignments.
CO readings should be taken by the Rapid Ascent Teams at five-floor intervals in tall buildings while they work the stairwells above the fire as they pause for rest. The reason this would be important to know is that if a "defend-in-place" operation is in effect and people are being advised to hold their positions on upper floors or are being directed back onto certain floors as they descend from the top of the building in a "re-entry and hold" posture, they may be placed in great danger. They may not even know CO is present, as it can indeed exist in areas where there is little to no carbon particulate matter present from the combustion process taking place many floors below.
(Note: Granted, in some instances, tenants working after hours who may be directed out of the attack stair onto certain unoccupied floors may not easily find the opposite stair to use for evacuation due to lights being off and confusing core layouts. In some cases, the other stair may not even be accessible due to secure tenant areas. A trailing search crew to the Rapid Ascent Teams may then have to be assigned to deliver groups of people over to the evacuation stair in such circumstances. The primary objective is for the Rapid Ascent Teams to confine their operations to the stairwells and not become bogged down or redirected onto floors to do searches or guide people to other stairwells.)
The Rapid Ascent Team concept now addresses three critical areas of concern for any incident commander:
- Directing people out of the attack stair and out of harm's way.
- Performing reconnaissance for the command post; to become the "eyes and ears" of the incident commander.
- Take CO readings at various intervals to determine where major pockets exist.
Of interest: The FDNY has CO detectors clipped to all chiefs' and company officers' radio straps that can be used in high-rise fires that show CO level. It reads 35–999 ppm (parts per million). It vibrates and emits an audible alarm at 35 ppm. Less expensive and less sophisticated CO detectors can be purchased that can easily clip onto fire gear of Rapid Ascent Team members that emit an alarm when a threshold limit of CO is reached that would also be effective for this application.