Fire Service Ventilation (7th Edition)
Chapter 5-Forced Ventilation
Test Review

  • Forced ventilation eliminates or reduces the effects of unstable and erratic winds.
  • Forced ventilation provides greater control of the fire situation by providing dependable, controllable airflow.
  • Forced ventilation allows flames, heat, and smoke to be directed away from occupants and uninvolved portions of the structure.
  • Forced ventilation can be utilized to channel products of combustion using the most efficient and least destructive path.
  • Forced ventilation allows fresh air to be introduced into the space.
  • Forced ventilation allows a tenable atmosphere to be obtained quicker.
  • Forced ventilation increases visibility and reduces fire and smoke damage.
  • Forced ventilation reduces interior heat levels and supplements natural air flow.
  • Forced ventilation improves survivability of occupants still inside.
  • Forced ventilation can greatly intensify the fire or fire spread.
  • Forced ventilation when misapplied, it can obscure vision, fail to reduce interior temperatures, and channel contaminants into exit passageways.
  • Ventilation equipment is sometimes dependant on a power source.
  • Gasoline blowers must be shut down to be refueled, interrupting the ventilation process.
  • Using hydraulic (fog stream) forced ventilation requires that a firefighter stay inside the atmosphere and ventilation must be stopped if their SCBA runs out.
  • Smoke ejectors are ducted fans of various sizes, usually in box-like housings.
  • Air-moving capacity is measured in cubic feet per minute.
  • Most smoke ejectors are electric, however, gasoline powered models exist.
  • Smoke ejectors must have explosion proof motors.
  • Smoke ejectors are sometimes fitted with flexible ducting to reach hard to access (confined) spaces.
  • Blowers are ducted and non-ducted fans that are used to blow fresh air into a space from outside the space.
  • Blowers are larger in size and rated capacity than smoke ejectors.
  • The majority of blowers are gasoline-powered, however, electric and hydraulically-powered units are available.
  • Some blowers are equipped with spray nozzles to inject water into the air stream, however, it has been found to be of little use in suppressing fires.
  • Hydraulic ventilation is most often used with handlines, however, adjustable master stream nozzles can be used.
  • Fire streams can be used to direct and control the airflow much as a smoke ejector by pointing the nozzle or portable adjustable master stream nozzle through a window or doorway.
  • Fog streams draw large amounts of smoke and heat out of the opening in the direction of the stream.
  • If a HVAC system is designed to draw air from the outside, it can aid in diluting and displacing cold smoke.
  • HVAC systems most often create a need for forced ventilation due to the fact that they circulate smoke throughout the structure.
  • Commercial climate control systems are normally just larger versions of residential systems.
  • Some commercial climate systems are equipped with basic fire-control features such as fire dampers in the ducts activated by fusible links.
  • Heavy-duty HVAC systems found in major mercantile occupancies, enclosed shopping malls, high-rise apartments and office buildings, and some heavy industrial occupancies are designed with features that will limit fire spread.
  • Some HVAC system include heat/smoke-activated dampers in the ducting, heat/smoke detection systems integrated into the alarm system, and automatic sprinkler protection.
  • Most important feature on some HVAC systems is that there may be a manual control for exhausting cold smoke.
  • Positive pressure ventilation counteracts the pressure being generated by the combustion process and/or by adverse winds.
  • Positive pressure ventilation is far more effective than negative pressure ventilation and much safer.
  • Positive pressure ventilation keeps interior temperatures cooler by introducing fresh air and improves visibility.
  • Blowers set up at ground level can force smoke out of high-rise structures more than 20 floors above.
  • When continued into the overhaul phase, positive pressure ventilation can aid in the detection of hot spots by supplying additional air which produces visible smoke sooner.
  • Attack crews must be ready before performing positive pressure ventilation.
  • Negative pressure ventilation draws cool, fresh replacement air into the space as contaminants are ejected.
  • With negative pressure ventilation, personnel and equipment usually must stay in the space being ventilated.
  • When natural ventilation does not effectively clear the space, forced ventilation may be needed.
  • Forced ventilation may be needed for below-grade fires.
  • With large spaces that natural ventilation would not work or be to time-consuming, forced ventilation is a better choice.
  • Windowless buildings or situations where access to fire is limited may benefit from forced ventilation.
  • Hydraulic ventilation moves 2 to 4 times more contaminants than ejectors when applied properly.
  • Hydraulic ventilation increases water damage to the structure and requires a substantial supply of water.
  • With freezing temperatures, icing may be a problem when using hydraulic ventilation.
  • Hydraulic ventilation operations must be halted when airpacks run out.