16 Ventilation

Question 1

Define ventilation?

Answer 1

Ventilation, as applied in firefighting, is the planned and systematic release and removal of heated air, smoke and toxic gases from a confined area and the controlled replacement of these products of combustion with a supply of cooler fresh air.

Question 2

What 4 factors must the FF consider pertaining to smoke?

Answer 2

1. Volume
2. Velocity
3. Density
4. Colour

Question 3

3 different cuts for roof ventilation openings?

Answer 3

1. Kerf cuts
2. Inspection cuts
3. Louvered cuts

Question 4

Find where you want the opening and think about the following?

Answer 4

1. Location of seat of fire
2. Wind direction
3. Extend of the fire
4. Obstructions
5. Exposures

Question 5

Who does ventilation have to be coordinated with?

Answer 5

Ventilation must be coordinated with fire attack - it is a systematic and controlled process involving coordination of which areas to ventilate. (ex. breaking windows, opening doors, roof cuts etc.)

Question 6

What are the means of achieving vertical or horizontal ventilation?

Answer 6

1. Natural
2. Forced/Mechanical
   - Electric fans
   - Hydraulic
   - Heating, ventilation and air condition systems (HVAC)

Question 7

What are the disadvantages of negative pressure ventilation (NPV) ?

Answer 7

1. Equipment block access and egress to the structure
2. FF must enter the the structure to initiate NPV
3. Equipment gets exposed to contaminants
4. Not effective in high ceiling structures
5. Produces additional noise within the structure
6. Must be used with electric fans only
7. Less adaptable to situation
8. Less effective than PPV
9. Depends on a power source (electricity, fuel)
10. Requires special equipment

Question 8

When should positive pressure ventilation (PPV) not be used?

Answer 8

Where the fire exists in an under-ventilated state or where any warning signs preceding backdraft are apparent!
It is well established that the addition of air into an under ventilated compartment could possibly trigger a backdraft, smoke explosion or even flashover.

Question 9

What are the advantages of PPV?

Answer 9

1. can be established without entering contaminated environments
2. Air currents are kept to a minimum
3. Equipment does not block doorways
4. Internal combustion equipment operates more efficiently (gas operated fans)
5. Equipment cleaning and maintenance is reduced
6. Noise levels are reduced within the fire building
7. It is effective in all types of occupancies
8. Heat and smoke can be directed away from paths of egress
9. It can be controlled
10. It is more effective than NPV or HV

Question 10

What are the disadvantages of PPV?

Answer 10

1. Must be coordinated with other sectors
2. Introduces large volumes of air into a structure that if misdirected will intensify and spread the fire
3. Requires special equipment
4. Depends on a power source (water, electrical, fuel)

Question 11

What % of the opening has to be covered, when ventilating with a fog stream (Hydraulic ventilation) ?

Answer 11

85 - 90%

Question 12

How far back does the nozzle tip have to at least be from the opening for HV?

Answer 12

At least 2 ‘ or 0.6m

Question 13

When are FF allowed to switch of the HVAC system?

Answer 13

1. when no qualified person is available

2. If it is a simple on and off switch

Question 14

Before attempting Hydraulic ventilation the fire must be?

Answer 14

1. placed under control to prevent further fire damage

2. contact fire command prior to ventilating

Question 15

The intensity of the stack effect will depend on?

Answer 15

1. How air tight the building is
2. The distance between the upper and lower openings
3. the difference between the inside and outside temperature

The greater the distance between upper & lower openings and the difference in temp. the more intense the stack effect will be.

Question 16

Depending on the factors of the stack effect, which four situations can occur.

Answer 16

1. Thermal layering
2. Natural stack effect
3. Reverse stack effect
4. Mushrooming

Question 17

What are 5 advantages of forced ventilation?

Answer 17

1. It is controllable
2. It can supplement natural ventilation
3. It is faster than natural ventilation
4. It reduces smoke damage
5. It aids property conservation

Question 18

What is mushrooming?

Answer 18

It is the lateral and downward migration of smoke when it encounters a physical barrier