TN 105.7- High Rise Ventilation Part 1

Ventilation in High-Rise Buildings

• Ventilation is a priority at any high-rise incident.

Mechanisms of Smoke Movement

• Five factors cause smoke to move throughout a high-rise building: Expansion, Buoyancy, HVAC Systems, Stack Effect, and Mushrooming Effect.
• Expansion and Buoyancy fill areas closer to the fire's origin with smoke.
• HVAC Systems and Stack Effect can rapidly fill the entire building with smoke.
• These four mechanisms can act in conjunction with one another to fill an entire building with smoke.

Expansion

• Heat from a fire causes gas to expand, typically three to four times in volume.
• In compartments with limited openings, this can cause an increase in pressure, driving smoke into adjacent compartments.

Buoyancy

• Superheated gases are less dense than the surrounding air and therefore more buoyant.
• This buoyant smoke/air migrates into adjacent compartments, particularly those above the fire compartment.

HVAC Systems

• A building's HVAC system can either enhance or interfere with the ventilation of smoke and gases.

Stack Effect

• The movement of air inside a tightly sealed building due to the temperature difference between the inside and outside of a building.

Mushrooming Effect

• Smoke that has migrated to the uppermost part of a building and been forced back down, in a boiling or rolling motion, by hotter, rising smoke and gases.

Tactical Considerations for the Ventilation Sector Officer

• The Ventilation Sector Officer may be Mobile or Static based on the size and complexity of the incident.

Investigation

• The Ventilation Sector Officer directs at least two Firefighters to each stairwell to determine smoke conditions.
• They travel each stairwell in its entirety, checking to ensure stairwell doors on each floor are closed and smoke conditions on each floor.
• They receive updates from personnel regarding smoke conditions at different floor levels.
• They notify the Incident Commander of smoke conditions and update them on changes.

Stairwell Strategy

• The Ventilation Sector Officer identifies the fire attack stairwell and evacuation stairwell.
• Attempts are made to restrict entry or remove occupants from fire attack stairwells.
• Ventilation strategies are developed in conjunction with stairwell search and secure initiatives.

Determine Fire Floor

• The Ventilation Sector Officer monitors communications from the primary team(s) regarding the location and extent of the fire and smoke conditions.

Determine Status of HVAC System

• If the air handling system is spreading smoke within the building, it should be manually shut down.
• The air handling system should remain operational if it is pressurizing uncontaminated areas or exhausting smoke from the fire area.

Positive Pressure Ventilation

• If building supply fans are not activated or unavailable, then Positive-Pressure Ventilation (PPV) must be implemented by firefighters.
• Use PPV as per TN 105.5 – Positive Pressure Ventilation if trying to pressurize stairwells and keep smoke contained.

Entry Control

• If the Ventilation Sector Officer is Mobile, all PITs are transferred to Entry Control.
• If the Ventilation Sector Officer remains Static outside the Controlled Area, crews shall PIT in with Ventilation Sector Officer or a dedicated Entry Control.