Ventilation

Question 1

What is the purpose of ventilation?

Answer 1

Improves the safety of people trapped in the building

Reduce damage to the structure and it’s contents from heat and smoke

Provide exposure protection to uninvolved areas or adjoining structures

Improves firefighting conditions by:
- Increasing visibility
- providing a non-toxic atmosphere
- reducing temperature inside the structure

Question 2

What are the types of ventilation?

Answer 2

Natural

Manual (vertical and horizontal)

Mechanical (positive or negative pressure)

Hydraulic (hose stream)

Question 3

How does ventilation negatively alter fire behaviour?

Answer 3

Promotes possibility of flashover

Increases risk of backdraught

Question 4

What should you consider when ventilating?

Answer 4

Availability of existing openings

Location of fire

Path for combustion products to be vented

The structure construction and condition

Wind direction

Exposure protection

Air handling system

Vertical and horizontal ventilation

Question 5

How should you naturally vent?

Answer 5

Windows on the windward are opened at a low point. Windows on the leeward side are opened at a high point (1.5 times the windward opening)

Question 6

What is the correct method for fog stream hydraulic ventilation?

Answer 6

60 degree cone angle

Operator (wearing BA) is positioned within a metre of the door or window. Branch tip should be at least 0.5 metres back

Stream covers 85 to 90 percent of the opening

Question 7

What are the disadvantages of negative pressure ventilation?

Answer 7

Contaminants are drawn through the fan

Blocks entrances

Difficult to operate efficiently

Question 8

What are the advantages of positive pressure ventilation?

Answer 8

Allows more efficient removal of smoke and heat from the structure

Can be set up without entering smoke filled environment

Placement does not interfere significantly with ingress or egress

Heat and smoke may be directed away from unburned areas or paths of exit

Can be initiated much quicker with fewer personnel

Quicker results

Will see immediate improvement in interior conditions

Question 9

What distances should fans be from the door for positive pressure ventilation?

Answer 9

2m for diesel fan with air pushed through entire doorway

4m for electrical fan with air cone taking up 2/3 of doorway