Photo by Ed Hadfield A typical modern high-rise office building is dependent on heating ventilation and air conditioning (HVAC) systems to remove smoke from stairwells and the fire floor. High-rise fires offer a wide array of unique challenges to fire service personnel. Most cities...
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.
Photo by Ed Hadfield
A typical modern high-rise office building is dependent on heating ventilation and air conditioning (HVAC) systems to remove smoke from stairwells and the fire floor.
High-rise fires offer a wide array of unique challenges to fire service personnel. Most cities across the United States have multi-story occupancies within their jurisdiction. In the State of California, a high-rise is defined as an occupancy over 55 feet, although most jurisdictions consider 75 feet, or four stories, the minimum for a high-rise. Fire service personnel must remember that the occupancy does not have to be the traditional skyscraper of 70 to 80 floors to be considered a high-rise building.
Ventilation considerations within these occupancies challenge the abilities of most fire service organizations. Key to those problems are the following:
- Building size, height, square footage, and layout
- Internal building systems and firefighters’ knowledge of those systems
- Equipment necessary to adequately ventilate the structure
- Knowledge of proper ventilation principles
- Staffing levels
Let’s consider these factors. Building size and footprint are important factors to consider in ventilation operations. Usually, the company assigned stairwell support is going to accomplish or start the ventilation operations on this type of incident. In most cases, that will be a first- or second-due arriving truck company.
Based on the staging location of fire apparatus and the amount of personnel assigned to that company, one or two positive-pressure ventilation (PPV) fans will be brought to the support stairwells. Most 21-inch PPV fans provide approximately 10,000 cfm operating at full capacity.
Photo by Ed Hadfield
There may be leakage of air depending on the height of the building and leakage within the stairwell.
With the initial setup of these fans at the base of the stairwell placing the fans in-series, they will begin the pressurization of the support stairwell, but will not be adequate to provide true ventilation of the fire floor. This is due in part to the amount of area within the building to be pressurized. The initial application of two fans generally will not accomplish the task.
If the responding firefighters have strong knowledge of the building systems, the assistance from the heating, ventilation and air conditioning (HVAC) system within the buildings will greatly assist in the ventilation efforts. In fact, most new high-rise occupancies are required to have systems in place that evacuate smoke and products of combustion from stairwells and the fire floor. However, systems are susceptible to failure and human error. If the system does not operate properly, the firefighters on scene must be capable of providing ventilation in the stairwells, the fire floor, and floors above the fire floor for adequate and effective search/extension operations. This is will generally be accomplished via PPV, although the limiting factors stated above must be taken into consideration.
To begin the ventilation series, place two PPV fans at the base or entrance of the support stairwell. Depending on the height of the structure, the size of the internal stairwell, the amount of leakage within the stairwell (leakage occurs with internal exhaust vents and plenums within the stairwells and adjacent areas), the next PPV fan should be placed approximately midway between the base and the fire floor. If the fire floor is located above the eighth floor, two PPV fans should be spaced one-third and two-thirds of the way between the base and the fire floor. (Note that in a high-rise incident, the rapid intervention team will be setting up one floor below the fire floor, and staging within the building will be established up to two floors below the fire floor.)
Photo by Ed Hadfield
The initial setup of two positive-pressure ventilation (PPV) fans at the base or entrance of the support stairwell. Depending on the height of the building, the next fan should be midway between the base and the fire floor. Figure 1. A pressure-reducing device on a hose outlet.