Chapter 13: Tactical Ventilation

Question 1

Air Flow

Answer 1

The movement of air toward burning fuel and the movement of smoke out of the compartment or structure.

Question 2

Blowers

Answer 2

Fans that are used to push fresh air into a structure. They may be powered by electricity, gasoline engines, or hydraulically. Blowers that are not intrinsically safe may only be used to push fresh air into the structure.

Question 3

Exhausted Opening

Answer 3

Intended and controlled exhaust locations that are created or improved at or near the fire to allow products of combustion to escape the building.

Question 4

Horizontal Smoke Spread

Answer 4

Tendency of heat, smoke, and other products of combustion to rise until they encounter a horizontal obstruction. At this point they will spread laterally (ceiling jet) until they encounter vertical obstructions and begin to bank downward (hot gas layer development).

Question 5

Horizontal Ventilation

Answer 5

Any techniques by which heat, smoke, and other products of combustion are channeled horizontally out of a structure by way of existing or created horizontal openings such as windows, doors, or other openings in walls. Typically portions of one or more of the horizontal openings will also serve as an air inlet.

Question 6

Hydraulic Ventilation

Answer 6

Ventilation accomplished by using a spray stream to draw the smoke from a compartment through an exterior opening.

Question 7

Kerf Cut

Answer 7

A single cut the width of a saw blade made in a roof to check for fire extension.

Question 8

Leeward Side

Answer 8

Protected side; the direction opposite from which the wind is blowing.

Question 9

Louver Cut or Vent

Answer 9

Rectangular exhaust opening cut in a roof, allowing a section of roof deck (still nailed to a center rafter) to be tilted, thus creating an opening similar to a louver. Also called center rafter cut.

Question 10

Mechanical Ventilation

Answer 10

Any means other than natural ventilation. This type of ventilation may involve the use of blowers and smoke ejectors.

Question 11

Natural Ventilation

Answer 11

Techniques that use the wind, convection currents, and other natural phenomena to ventilate a structure without the use of fans, blowers, and smoke ejectors.

Question 12

Negative-Pressure Ventilation (NPV)

Answer 12

Technique using smoke ejectors to develop artificial air flow and to pull smoke out of a structure. Smoke ejectors are placed in windows, doors, or roof vent holes to pull the smoke, heat, and gases from inside the building and eject them to the exterior.

Question 13

Positive-Pressure Ventilation (PPV)

Answer 13

Method of ventilating a room or structure by mechanically blowing fresh air through an inlet opening into the space in sufficient volume to create a slight positive pressure within the thereby forcing the contaminated atmosphere out the exit opening.

Question 14

Recirculation

Answer 14

Movement of smoke being blown out of a ventilation opening only to be drawn back inside by the negative pressure created by the ejector because the open area around the ejector has not been sealed.

Question 15

Smoke Ejectors

Answer 15

These are electrically powered fans that have intrinsically safe motors that are placed in the smoke-filled atmosphere to push the smoke out. They can also be used to push fresh air into the structure. They require the use of electrical cords and generators to operate.

Question 16

Stack Effect

Answer 16

Phenomenon of a strong air draft moving from ground level to the roof level of a building. Affected by building height, configuration, and temperature differences between inside and outside air.

Question 17

Trench Ventilation

Answer 17

Defensive tactic that involves cutting an exhaust opening in the roof of a burning building, extending from one outside wall to the other, to create an opening at which a spreading fire may be cut off. Also known as strip ventilation.

Question 18

Vertical Ventilation

Answer 18

Ventilating at a point above the fire through existing or created openings and channeling the contaminated atmosphere vertically within the structure and out the top. Done with openings in the roof, skylights, roof vents, or roof doors.

Question 19

Windward Side

Answer 19

The side or direction from which the wind is blowing.