Fire Service Ventilation (7th Edition)
Chapter 6-High Rise Structures & Special Situations
Test Review

  • Limited access, multiple compartments, masses of occupants, falling glass/debris, smoke/fire spread through vertical shafts, locked interior doors, low water pressure to upper floors, and crew fatigue are challenges of high-rise fires.
  • Low rise elevators access lower floors and must not serve the fire floor to be considered low rise.
  • High rise elevators provide access to upper floors.
  • Express elevators run non-stop from ground floor to top floor.
  • Freight elevators are designed to carry large, heavy loads.
  • Elevator car may be automatically called to the fire floor due to a control malfunction.
  • Power failure may strand an elevator above the fire or between floors.
  • Products of combustion rise through vertical openings until they encounter an obstruction or until their temperature is reduced to the temperature of the surrounding air.
  • Equalization of the pressure of rising smoke vertically to a point where it is equal with pressures outside the space causes the combustion products to lose their buoyancy, cease to rise and "stratify".
  • The three most common ventilation techniques for high-rise structures are vertical ventilation, horizontal ventilation of the fire floor, and horizontal ventilation of the floor above and below the fire floor.
  • Vertical ventilation in high-rises can prevent or reduce the chance of mushrooming.
  • Vertical ventilation in high-rises does not promote lapping.
  • Automatic smoke vents may eliminate the need for additional top ventilation.
  • Getting the vent group and equipment needed to the roof, roofs are out of reach of aerial devices, and intensity of the stack effect are common problems associated with high-rise ventilation.
  • Use of aerial apparatus is the fastest, safest, most direct method of ventilating high-rises.
  • Most roofs are out of reach of aerial ladders.
  • Interior stairways may be congested with escaping occupants.
  • Not all stairwells penetrate the roof, so pre-incident inspection is a must.
  • Use of helicopters is the most direct way of moving the vent team and equipment to the roof and removing occupants from the roof.
  • Level of coordination with the use of helicopters is extremely high and dependent on training, pre-incident planning, and smoke/weather conditions.
  • Stairwell bulkheads on the roof must be blocked open or removed from hinges.
  • Ventilation must be delayed until occupants above the fire floor are either evacuated or moved to an area of refuge.
  • Stairwells used for ventilation should not be used for fire attack.
  • The greater the distance between upper and lower openings and the greater the difference in temperature, the more intense the stack effect.
  • If it is hotter inside than it is outside, the airflow will be inward at the bottom and outward at the top.
  • If it is hotter outside than it is inside, the airflow will be outward at the bottom and inward at the top.
  • If temperatures are equal inside and outside, no natural airflow will take place.
  • Wind produces a positive pressure on the windward side which tends to raise the neutral pressure plane.
  • Negative pressure exists on the leeward side of a building, which lowers the neutral pressure plane.
  • Ventilating on the windward side can work against effective ventilation and spread fire into uninvolved areas.
  • Ventilating horizontally, below the neutral pressure plane will cause air to be drawn inward. Ventilating horizontally, above the neutral pressure plane will cause air to escape.
  • The closer ventilation is to the neutral pressure plane, the less the effect of negative or positive pressure.
  • Ventilating below the fire floor is useful when smoke has spread to floors below the fire floor due to negative stack conditions or mushrooming.
  • The most common technique for ventilating below the fire floor is to vent these floors horizontally which can be enhanced by pressurizing the entire building.
  • Ventilating below the fire floor is not a common practice.
  • Ventilation of the fire floor is difficult, time-consuming, and potentially dangerous to those on the street below due to falling glass that must be broke to effect horizontal ventilation.
  • Ventilating above the fire floor is the most effective method if the process is started at the top of the building.
  • The addition of controllable dampers to HVAC systems which can be selectively opened and closed can serve as smoke-control systems.
  • HVAC systems can limit spread of smoke/fire, improve operating conditions, and increase survivability of occupants.
  • HVAC systems used to control smoke movements should be operated by a qualified building engineer.
  • HVAC systems may be used to assist in locating the origin of the fire.
  • HVAC systems should be used to limit the extension of the fire and smoke to the smallest possible area.
  • HVAC systems should NOT promote the growth or extension of fire or smoke beyond the area of origin.
  • HVAC systems should provide fresh, uncontaminated air to any occupants who may still be trapped or located in a safe refuge area.
  • HVAC systems can be shut down automatically by smoke detectors in the ducts in the event smoke enters the ducts.
  • HVAC systems can be manual shut down by the building engineer.
  • Contact with the building engineer should be made as soon as units arrive at the incident to avoid delay in shutting down HVAC systems.
  • Automatic roof vents, which take advantage of convection, eliminate the need for additional ventilation by the fire department.
  • Automatic roof vent fusible links may fail, locking mechanisms may fail, sprinkler heads near them may prevent heat which activates them, and they create a large open space that firefighters may fall into while on the roof.
  • Atrium vents lend themselves to the stack effect and are usually accompanied by automatic vents to further rid contaminants.
  • Sprinklers may cool the surrounding air around atrium vents so that they do not open.
  • Monitors utilize a fusible link to open automatically to effect ventilation, but may be manually opened by removing the metal, glass, wired glass, or louvered sides.
  • Fusible links on monitors may fail and glass designed to break may not.
  • Skylights can open automatically in fires due to the glass breaking or thermoplastic cover melting.
  • Skylights with panes which have not been broken can be easily used for ventilation by breaking out the pane.
  • Skylight panes made of wired glass must be removed and cannot be effectively broken for ventilation purposes.
  • Curtain boards usually confine a fire to a relatively small area and may accelerate the activation of automatic sprinklers.
  • Curtain boards may slow or prevent the activation of roof vents.
  • If an opening of adequate size can be made opposite the point of entry in an underground structure, the fastest way to ventilate is to set up positive pressure blowers at the point of entry which allows the vent group to stay out of the underground area and still ventilate.
  • While ventilating an underground structure, the rest of the structure should constantly be monitored for signs of fire extension though walls or vertical channels.
  • The absence of exterior windows severely limits horizontal ventilation opportunities and increases the chances of backdraft and flashover conditions.