Positive Pressure Ventilation Standard Operating Procedure

Objective and Equipment for Positive Pressure Ventilation (PPV)

  • Objective: To facilitate the rapid and systematic removal of smoke and gases from structures during firefighting operations by utilizing the concepts of positive pressure ventilation.

  • Required Equipment:

    • Gas Powered Positive Pressure Fan: Must be a 21" Power Blower with a 4-cycle engine, capable of an output of 7890+ cubic feet/minute (cfm)7890+ \text{ cubic feet/minute (cfm)}.

    • Electric Powered Smoke Ejectors: Available in sizes of 16", 20", and 24".

Applicable Structures for PPV

  • Positive Pressure Ventilation may be utilized on a diverse range of structures, including but not limited to:

    • Single and Multiple Family Dwellings.

    • Apartment Buildings.

    • Hi-Rise Buildings.

    • Malls.

    • Windowless Buildings.

    • Basements.

    • Attics.

    • Strip Stores.

General Information and Tactical Principles

  • Strategic Application: PPV is an additional tactic for the Company Commander to consider and is most successful when used on confined space fires. It is not applicable to every fireground incident.

  • Personnel and Roles:

    • A fireground ventilation officer should be established during initial suppression operations. This individual must be familiar with PPV principles and practices.

    • Ventilation is most effective when exactly ONE firefighter and the Officer in Charge (OIC) implement and control the operation.

    • Effective communication is paramount for implementation.

  • Regulation of Airflow:

    • The size of the discharge opening must be regulated to control interior pressure. High interior pressure increases the speed of smoke removal.

    • Methods to control discharge size include using only the top portion of a window or opening a sliding/overhead door only 1/41/4 of the way.

    • Wind Direction: Pressurization should occur from the windward side, with exhaust directed to the leeward side, particularly on windy days.

  • Operational Setup and Fan Placement:

    • Multiple Fans: Fans can be used in series (pressure mode) or parallel (volume mode).

    • Mixed Sizes: If using fans of different sizes, place the larger fan in front of the smaller fan to utilize its higher cfmcfm output. The smaller fan behind it maintains the seal.

    • Exact Placement Distances: The front fan is placed 2−3 feet2-3 \, \text{feet} from the opening. The back fan is placed 5−6 feet5-6 \, \text{feet} away to maintain the cone seal.

    • Removal of Obstructions: Screens must be removed from windows to increase airflow by 30%−40%30\%-40\%. Curtains should be removed or tied back.

  • Safety Constraints:

    • PPV is NOT to be used in suspected backdraft situations.

    • Large loading dock doors should be closed halfway (1/21/2 way) to reduce the opening size.

    • Timing: Ventilation must not start until personnel are ready to attack the fire within approximately 15 seconds15 \, \text{seconds}, ensuring an exhaust opening exists before starting the blower.

Specific Applications: Dwellings and Basements

  • Single Family Dwellings (One Story):

    • Place fan 5−6 feet5-6 \, \text{feet} from the door to seal the opening in a "cone" fashion. Proper placement is verified by feeling for airflow around the opening with a bare hand.

    • Establish a single pathway using a single discharge opening (door or window) on the opposite side of the structure to follow natural airflow.

    • Compartmentalization: If many windows are removed during suppression, PPV is achieved by opening and closing individual doors to isolate rooms.

  • Single Family Dwellings (Multiple Stories):

    • Clear the first floor first while keeping upper floor openings closed.

    • Once the first floor is clear, close its discharge opening to force air upward into the second floor.

  • Basements (No Exterior Openings):

    • Requires two fans. Position a 16" electric fan at the top of the stairs blowing down to avoid introducing carbon monoxide fumes from gasoline fans.

    • The electric fan should NOT seal the opening; place it close to the door to force air through the bottom half (1/21/2) of the doorway while smoke exits the top half (1/21/2).

    • The second fan pressurizes the rest of the building as usual, moving air across the basement entrance toward a discharge opening on the opposite side of the structure.

  • Basements (Existing Openings):

    • Close the opening between the basement and the first floor to prevent smoke spread.

    • Pressurize the area using the same procedure as dwellings. A fan can be placed at the basement opening on the floor above.

    • Mechanical Warning: 4-cycle PPV blowers must not be laid horizontal, as the oil will fail to lubricate the engine.

Specific Applications: Attics, Strip Stores, and Large Structures

  • Attics:

    • Clear the area of the building most likely to receive smoke damage before opening attic hatches or doors.

    • Seal the entrance in a cone fashion. Use existing louvers, turbines, or cut a ventilation hole in the roof.

    • Monitor roof operations closely during fire attack.

  • Strip Stores:

    • Follow single-story dwelling guidelines.

    • Exhaust the farthest occupancy where smoke is entering. Once clear, close the discharge opening to limit spread and move to adjacent occupancies.

    • Check void spaces above drop ceilings for fire extension.

  • Multi-Story, High-Rise, and Windowless Buildings:

    • Identify an enclosed stairwell with roof access. If smoke is present, send a firefighter equipped with SCBA, a spare bottle, and a portable radio to the top, closing all doors on the way up.

    • Pressurize in series: First fan 5−6 feet5-6 \, \text{feet} from door, second fan 2−3 feet2-3 \, \text{feet} in front of the first.

    • Ventilate floors from the lowest involved floor upward.

    • Chimney Effect: One stairwell provides fresh air while another (with roof access) serves as a "chimney" to exhaust gases. Elevator shafts may also be used if roof and floor access are present.

  • Smokeproof Enclosure Ventilation Systems:

    • Common in new High-Rise and Mid-Rise construction. These are independent systems activated by smoke detectors at stairwell entrances.

    • These shafts have dampered relief openings and supply a minimum positive pressure of 2500 cfm2500 \, \text{cfm} through the relief opening while maintaining stairwell pressure.

    • Command Actions: The Company Commander must find the annunciator panel (usually near the main entrance) and activate the stairwell pressurization system. If using the stairwell for smoke removal from a specific floor, the exhaust system must be shut off to avoid "fighting" the system.

    • Height Considerations: In buildings over 15 stories, an additional fan may be required in the intake stairwell at the level being cleared.

Apartment Complexes, Malls, and Aircraft

  • Apartment Complexes:

    • Open Stairwells: Fan placed 3−5 feet3-5 \, \text{feet} outside the main entrance to maintain access/egress.

    • Enclosed Stairwells: Discharge options include exhausting through an involved or uninvolved apartment, removing glass at the uppermost landing (use extreme caution), or cutting a roof hole above the stairwell scuttle hatch.

  • Malls:

    • Individual stores are treated like strip stores. Large areas require a single opening/discharge point with multiple fans (in-line or parallel) and booster fans inside.

    • Internal HVAC equipment may be used, though caution is required regarding heat and smoke spread.

  • Aircraft Emergencies:

    • Position fans at entry points: front passenger entrance, over-wing emergency exits, or rear food service entrances.

    • For high/hard-to-reach points, hang the fan on an "A" frame ladder or place it on a mobile stairwell to move it into position.