Ventilation

Session Reference: 1-3 Topic: Ventilation Time Required: 90 Minutes References:    • Truck Company Fireground Operations, Second Edition, Chapters 4 and 5    • Essentials of Fire Fighting, Third Edition, Chapter 7...


      d. If roof is flat, opening should be made at hot spot

      e. On gabled roof, opening should extend from hot spot to peak

      f. Draft can be increased by making an additional opening just above the eave line on side opposite

         original opening

      g. Care should be taken so that opening does not increase fire spread

IV. Forced Ventilation (1-3-4)

A. Smoke ejectors

  1. Cannot be used as a substitute for natural venting techniques

      a. Heat, smoke, and gases most effectively removed by natural convection through natural or

          forced openings

      b. Crews should perform natural ventilation and carry out other necessary duties

      c. Fans should not be used in partially or completely confined spaces in which there is fire

      d. May be used in confined areas after fire has been knocked down

  2. Fan placement

      a. Most effective when placed where they tend to increase natural air flow

      b. When fans are positioned in windows or doorways, all shades, drapes, blinds, curtains, and

           screens should be removed

      c. If possible, open area around fan should be closed to increase fan efficiency by directing air

         through opening and preventing smoke from re-entering

      d. Be careful not to exhaust smoke into congested areas or into heating and cooling intakes

  3. Fans in tandem

      a. Can be especially effective when used in pairs

      b. Place one fan near an outside opening blowing smoke out and other inside room to blow smoke

          to first fan

      c. Fans can be used to exhaust smoke and draw in fresh air at same time

      d. Exhaust fan should be mounted high in vent opening

      e. Intake fan should be lower

B. Positive pressure blowers

  1. Introduction

      a. Fresh air introduces to increase pressure

      b. Selective process of opening and closing doors and windows

      c. Initiated outside structure

      d. Has potential of moving fire and fire gases

      e. Generally speaking, initiated between fire fighters and fire or between fire and trapped victims

  2. Advantages of positive pressure ventilation

      a. Can maintain primary and secondary egress routes

      b. Does not require explosion proof fans

      c. Can be initiated from exterior of building

      d. Effective on all structures when doors and windows maintained

      e. Does not require smoke and fire gases to pass through fan

      f. Quicker than negative ventilation

     g. Air velocity within building increased

     h. Works well in large areas

  3. Fan placement

     a. Place fan far enough away from door to fill opening with cone of air

     b. Stacking fans increases volume greatly

     c. For oversized doors, place fans side by side or in tandem

     d. For single fan, place 6 to 10' from doorway

     e. For multiple fans, place 3 to 5' from doorway

  4. Working with positive pressure

     a. Ventilation critical to overall operation

     b. Must identify location of fire

     c. Place pressure zone to support rescue or fire attack

     d. Take care not to destroy integrity of doors and windows

  5. Special situations

     a. High rise buildings

     b. Heavier than air gases and below grade conditions

     c. Confined space

     d. Emergencies involving temperatures

C. Fog streams

  1. Can be used to start venting immediately after fire has been knocked down

  2. To be most effective, stream should be positioned so fog pattern covers most of window opening

  3. Hold nozzle few feet inside window

  4. Observe smoke movement to determine proper position of nozzle

  5. Fog streams should not be used for venting if they damage

      a. Items removed for protection

      b. Outside of fire building or enter adjourning buildings

      c. Inside of room from which directed

  6. They should not cause ice to form outside