Fire Rescue SOP 420-05 Ventilation

• SOP 420-05 provides guidelines for Fire Rescue to make decisions about using mechanical or natural ventilation, which was issued May 21, 2018 and effective June 21, 2018
• It aims to remove Immediately Dangerous to Life or Health (IDLH) atmospheres using horizontal or vertical techniques, like positive or negative pressure.
• The Fire Rescue Administrator is responsible for implementing the guidelines.
• The guidelines apply to all Emergency Operations personnel.
• Attachments include the Super Vac P164 Series Fan Manual and the RAMFAN Manual.

General Information

• Ventilation efforts should improve the safety of civilians and firefighters, and need to be coordinated with fire attack operations.
• Highly specific situations such as confined spaces or highrises will require specialized ventilation methods not covered by this document.

Basics of Ventilation

• Three core principles when ventilating are life safety, fire containment, and property conservation.
• Ventilation helps clear contaminated atmospheres, improving occupant survival chances.
• Releasing contaminated atmospheres to the exterior stops interior spread, while ventilation helps to limit property damage.
• Incident Commanders determine ventilation type (vertical/horizontal) and method (natural/mechanical).

Ventilation Types

• Vertical ventilation uses the tendency of heat to rise, employing openings so contaminated air goes vertically out of the structure.
• Stairwells, exhaust vents, skylights, and roof openings act as pathways.
• Openings can be made by cutting holes in roofs or floors.
• Horizontal ventilation works in basic ventilation situations, using available doors, windows, and horizontal openings.
• Horizontal ventilation is generally safer and faster than vertical.

Ventilation Methods

• Natural ventilation relies on convection currents, wind, and natural air, while wind speed/direction is a factor.
• Mechanical ventilation introduces or exhausts air using fans or powered equipment.
• The three types of mechanical ventilation are negative pressure, positive pressure, and hydraulic.
• Negative pressure uses fans to exhaust contaminated air
• Positive pressure uses fans to push clean air in and contaminated air out, directing clean air toward exhaust openings.
• Hydraulic ventilation uses fog or broken fire streams creating a pressure differential via the nozzle.
• HVAC systems (positive or negative pressure) in some buildings provide mechanical ventilation or smoke management.

Vertical and Horizontal Ventilation

• Due to resource availability, building construction, and potential risks, alternative ventilation options may be considered.
• Reference SOG 420-06 Roof Operations for Vertical Ventilation.
• Negative pressure ventilation uses an electric fan like the Super Vac P164 Series, placed high in a door or window on the leeward side.
• RAMFAN, a high-volume velocity fan, supports PPV with a capacity of up to 13,000 cfm of air.
• The high-volume fan should be placed on the windward side, 4-10 feet away from the ventilation opening, ensuring the air cone covers the opening.
• When using PPV when selecting an exhaust opening on the leeward side include the following conditions:
  • Close to the fire
  • 1-2 times the ventilation opening size
• When cooler gases with less energy are being ventilated, smaller exhaust opening sizes can be used
• To expedite the process, doors to rooms may be closed.

Situations Where PPV should be Avoided

• PPV should not be used when these conditions are present:
  • When the fire's location is unknown
  • When the fire is not under control
  • When pre-flashover conditions include high heat, turbulent smoke, roll-over, uncontrolled interior fire, and auto-ignition
  • In void spaces like chases, floors, walls, and attics
  • If there are no exhaust openings
  • When there are strong winds against the exhaust opening.