Principles of Positive Pressure Ventilation for Firefighting

1. Principles of Positive
Pressure Ventilation

2. Principles of Positive
Pressure Ventilation
VIDEO
2
KEY CONCEPTS:
REDUCE HEAT
REDUCE SMOKE
IMPROVE
VISIBILITY
COMMUNICATION

3. Principles of Positive
Pressure Ventilation
3
OVERVIEW
I. PRINCIPLES OF PPV
II. LOCATION
III. MANAGING AIRFLOW
IV.SUCCESSFUL PPV
V. OPERATIONAL CONSIDERATIONS
VI.ADVANTAGES AND DISADVANTAGES OF PPV

4. Principles of Positive
Pressure Ventilation
4
Principles of PPV
A. Use to supplement natural airflow
1. Note prevailing wind direction
2. Do not try to reverse convection
What is convection?
The transfer of heat energy by the
movement of heated liquids or gases
(heated air and gases rise)
A. Use high volume fans
B. Create pressure differential
1. High pressure inside
2. Low pressure outside
C. Smoke seeks an outlet through an opening
controlled by fire fighters
4

5. Principles of Positive
Pressure Ventilation
5
Principles of PPV
Use high volume fans
Gas
Electric
5

6. Principles of Positive
Pressure Ventilation
6
Principles of PPV
Create pressure differential
High pressure inside
Low pressure outside
6

7. Principles of Positive
Pressure Ventilation
7
Location
A. Outside of
building
1. Fans produce
carbon
monoxide
B. At lowest point of
building
C. Cone of air must
fully cover
opening

8. Principles of Positive
Pressure Ventilation
8
Managing Airflow
A. Systematic process
1. Exhaust opening should be smaller than input opening
2. A single exhaust opening is preferred
a) Multiple exhaust openings will reduce
effectiveness
3. If size of exhaust openings exceeds size of input opening
positive pressure will be lost
B. Direct airflow by opening and closing doors
1. Work one room at a time
C. Multistory buildings
1. Apply airflow at lowest level of building
a) Use stairwells or vertical shafts to direct airflow
2. Work one level at a time
a) Begin with level most heavily charged with smoke
b) Open and close doors to direct airflow
1. Smoke can be directed out exterior openings
on fire floor
2. Smoke can be directed up vertical shafts that
extend through the roof

9. Principles of Positive
Pressure Ventilation
9
Successful PPV
A.Good communications
B.Discipline
C.Building occupants may
compromise operations
1.Occupants leaving building may
alter airflow
2.Curious occupants open doors
and interfere with operations
3.In large buildings it may be
necessary to detail personnel
to patrol openings

10. Principles of Positive
Pressure Ventilation
10
Operational
Considerations
A. Exhaust openings
1. PPV is not effective if smoke and heat have no
where to go (vertical ventilation)
2. Remove screens, etc.
B. Fan placement
1. Spot fan so that cone of air covers entire
opening
2. Multiple fans can be used for large openings
a) Arrangements include side by side,
stacked, inline
3. PPV fans will introduce small amounts of
carbon monoxide into buildings (from
exhaust)

11. Principles of Positive
Pressure Ventilation
11
Advantages &
Disadvantages of PPV
A. Advantages
1. Set up without entering building
2. Most efficient forced ventilation
technique
3. Effective in very large buildings
B. Disadvantages
1. Structure must be intact (crews must have
the ability to control openings)
2. Introduces carbon monoxide into
structure (exhaust-gas fan)
3. May extend hidden fires

12. Principles of Positive
Pressure Ventilation
VIDEO-Bad PPV
KEY CONCEPTS:
COMMUNICATION
EGRESS
VERTICAL
PLACEMENT
12

13. Principles of Positive
Pressure Ventilation