Back To Basics: Effective Ventilation


b. Fan placement

1) Most effective when placed where they tend to increase natural air flow

2) When fans are positioned in windows or doorways, all shades, drapes, blinds, curtains, and screens should be removed

3) If possible, open area around fan should be closed to increase fan efficiency by directing air through opening and preventing smoke from re-entering (churning of air)

4) Be careful not to exhaust smoke into congested areas or into heating and cooling intakes

5) Fan can be hung in windows or on doors, in doorways using compression devices, or on the underside of ladders

c. Fans in tandem

1) Can be especially effective when used in pairs

2) Place one fan near an outside opening blowing smoke out and the other fan inside room to blow smoke to first fan

3) Fans can be used to exhaust smoke and draw in fresh air at same time

4) Exhaust fan should be mounted high in vent opening

5) Intake fan should be lower

4. Positive pressure blowers

a. Introduction

1) Fresh air introduced to increase pressure

2) Selective process of opening and closing doors and windows - effective on all structures when doors and windows maintained

3) Initiated outside structure

4) Has potential of moving fire and fire gases

5) Generally speaking, initiated between fire fighters and fire or between fire and trapped victims

6) Can maintain primary and secondary egress routes

7) Quicker than negative ventilation

8) Works well in large areas

b. Blower placement

1) Place fan far enough away from door to fill opening with cone of air

2) Stacking fans increases volume greatly

3) For oversized doors, place fans side by side or in tandem

4) For single fan, place 6’ to 10' from doorway

5) For multiple fans, place the first blower 3’ to 5' from doorway (if different size blowers, place the larger blower in front)

5. Fog streams

a. Can be used to start venting immediately after fire has been knocked down

b. To be most effective, stream should be positioned so fog pattern covers most of window opening

c. Hold nozzle two feet inside window

d. Observe smoke movement to determine proper position of nozzle

e. Fog streams should not be used for venting if they damage

1) Items removed for protection

2) Outside of fire building or enter adjourning buildings

3) Inside of room from which directed

f. They should not cause ice to form outside

g. Should be short term operation

D. Vertical Ventilation

NOTE: Ladders should be used to provide safer footing for any pitched roof operation and to spread the load on any flat room. There should always be two means of escape for any roof operation and a protection hoseline should be in place on the roof. Roofs should also be checked to make sure they are safe to work on. Spongy material, bubbling tar, melted snow or dry spots on a roof, or smoke or heat emitting from the roof are some of the signs that the integrity of the roof may be compromised.

1. Natural Roof Openings

a. In multi-story buildings, vertical shafts which extend the full height of the building carry stairways, elevators, dumbwaiters, electric wiring, heating ducts, and plumbing and sewer pipes

b. Convected heat, smoke, and gases will rise within and around shafts

c. If shafts are not vented at top, fire will travel horizontally

d. Pressure will force heat, smoke, and gases throughout upper part of building

e. Shafts are capped at roof with various closures (make sure of area being vented when cap is removed)

2. Cutting Through Roofs

a. At times, only way to properly ventilate is cut hole in roof

1) Roof made of boards can be cut with axe

2) Roof may of plywood should be cut with circular or chain power saw

3) Care should be taken not to cut joists or other structural members

b. Single large hole is more effective than several small holes

1) One 4' X 4' hole has twice area of four 2' X 2' holes

2) All roof boards should be cut through before any pulled up

3) Keep back to wind when pulling boards

4) When all boards ripped up, make opening in ceiling below

c. Special care should be taken when fire is immediately below roof