AUC 349 Smoke control using positive pressure fans Flashcards
What are the 3 uses of the PP Fans?
Fans can be used to pressurize the attack and evacuation stairwells to either keep heat and smoke from entering stairwells or to sequentially ventilate floors of a building. They are also used to mechanically ventilate large structures or areas.
What equipment does the Ventilation Support Group report to the command post with?
4.1 The Ventilation Support Group shall report to the Incident Command Post (ICP) with the
following equipment: 27 inch Tempest PPF and exhaust hoses, eye and ear protection,
Dave Clark headset and handie-talkies, CO monitors, elevator keys, Halligan and heavy axe (for elevator operations), door chocks, hand lights, SCBA and full PPE.
What are the 4 designations of the Ventilation support group?
6.1 The officer shall be designated as the “Vent Group Supervisor”. The members assigned to operate the fans shall be designated “Vent Group Lobby Unit” and the “Vent Group Fire Unit.” The member assigned the roof shall be “Vent Group Roof”.
Which stairwell is the 1st consideration for pressurization?
6.2 The attack stairwell is the first consideration for pressurization and will be pressurized upon the order of the IC. The evacuation stairwell shall be pressurized when necessary, or for sequential ventilation.
Who authorizes stairwell pressurization with the PPF’s?
6.3 Stairwell pressurization will not be initiated until authorized by the Incident Commander.
When negative results are encountered how do we discontinue pressurization of the stairwells?
6.4 PPFs in operation should never be left unattended; a radio-equipped member must continually monitor each operating fan. If negative results are encountered, discontinue pressurization by throttling down fans to idle, and closing the door to the stairwell that the fan is pressurizing.
What are the priority uses of the PPF’s?
- 5 The priority order for the use of PPFs is as follows:
- Pressurizing the attack stairwell to support the fire attack, by controlling the smoke condition at the attack stair doorway and throughout the attack stairway.
- Pressurizing the evacuation stairwell for smoke and CO control.
- Ventilating the public hallways for smoke and CO control.
What is the optimum placement of the PPF’s?
The optimum placement of the PPF is 4 to 6 feet from the attack stairway door on the ground
floor and directly facing the door to the stairwell at an angle tilt of 80 degrees. This placement in front of the doorway will create the proper seal at the stairwell inlet. The 80 degree angle tilt can be achieved by using the tilt angle index holes on the base on the fan frame. There are 5 tilt positions operated by a foot pedal. The fan shall be positioned to blow into the stairwell; it should not be placed in the stairwell.
1 fan can provide proper pressure up to how many stories?
How many stories will 2 PPF’s pressurize?
7.3 Research and field experience has proved that one fan can provide the proper pressure in the stairwell up to 10 stories depending on conditions, and two fans will pressurize a 40 story building when properly positioned. If the fire floor is above the 10th floor or additional pressures are required to maintain the stairwell free of smoke, a second fan must be brought to three floors below the fire floor and set up, following the proper positioning (4 to 6 feet back, 80 degree angle). This will maintain proper pressure throughout the stairwell, up to a 40 story building. This same concept, of placing a fan on the ground floor and a second fan three floors below the fire, can also be applied to buildings greater than 40 stories.
In most situations, in order to maintain pressure in the stairwells, doors must remain closed including the bulkhead. However, if on arrival the IC gets information from the units operating that there is an extreme smoke condition in the attack or evacuation
stairwell, ventilation of that stairwell may be implemented as follows when units are NOT committed to the fire floor?
7.5 When units are not committed on the fire floor:
PPF shall begin pressurization on the ground floor (or alternate site due to fan noise) with the fire floor stairwell door closed. Vent group roof or another designated member shall open the stair bulkhead door (burp the bulkhead), until smoke clears (approx. 60 seconds), then shut the bulkhead door. During this time, the pressurization will be maintained in the stairwell with the bulkhead door open or closed.This member will need to stay in that position on the roof to coordinate stairwell ventilation.
In most situations, in order to maintain pressure in the stairwells, doors must remain closed including the bulkhead. However, if on arrival the IC gets information from the units operating that there is an extreme smoke condition in the attack or evacuation
stairwell, ventilation of that stairwell may be implemented as follows when units ARE committed to the fire floor?
7.6 When units are committed on the fire floor:
PPF shall begin pressurization on the ground floor (or alternate site due to fan noise). The fire floor stairwell door should be closed as much as possible and still allow handline access. Vent group roof or another designated member shall open the stair bulkhead door (burp the bulkhead), until smoke clears (approx. 60 seconds) then shut the bulkhead door. During this time the pressurization will be maintained in the stairwell with the bulkhead door open or closed. This member shall remain at the roof to coordinate stairwell ventilation.
Note: In either situation, the higher pressures in the stairwell created by the fans, will limit the heat and smoke on the fire floor from traveling into the stairwell.
Why is it recommended that we keep a member at the stairwell door during pressurization?
7.7 Note: It is recommended that a member on the fire floor remain in position at the stairwell door at all times. This member will be able to keep the stairwell door closed as possible in order to maintain pressurization, control smoke movement and convection currents. This member will also be able to direct (sounding) members back to the stairwell if needed in a heavy smoke condition.
What is the process of sequential ventilation?
8.2 The process may be implemented as follows:
-Confirm that the attack stairwell is clear of members and civilians.
-The bulkhead (top vent) should be opened in the attack stairwell. All other doors in the attack stairwell should remain closed. The evacuation stairwell bulkhead remains closed.
-Opening the stairwell doors on the fire floor, both in the attack and evacuation stairwells will cross-vent the fire floor, by removing contaminated smoke from the fire building via attack stairwell.
-This ventilation can be carried out floor by floor if smoke or CO contamination occurs on multiple floors. Start at the lowest point of contamination and work towards the top of the building. For taller buildings additional fans may be required in the evacuation stairwell to achieve adequate pressures.
Note: This sequential ventilation process can be implemented when a building has high levels of CO or other contaminates. The process will begin on the ground floor or cellar and continue on each floor until the CO is reduced to acceptable levels. PPF exhaust should be vented to the exterior if possible to reduce the introduction of CO into the building. Electric fans can also be implemented in this situation. If CO levels are in the 0 to 60 ppm range, gasoline powered PPFs will not significantly reduce those levels due to the CO emissions produced by the fans.
- POSITIVE PRESSURE MECHANICAL VENTILATION OF LARGE STRUCTURES/AREAS
9.1 Mechanical ventilation of large structures or areas can be accomplished in a relatively
short time as compared to natural ventilation. The concept of creating a higher pressure (the interior) that is inclined to move to a lower pressure (the exterior), will allow for the controlled movement of the toxic atmosphere to clear that large structure or area.
9.2 The process may be implemented as?
-When the seat of the fire is determined and the fire is controlled by a sprinkler or handline, look for an exhaust opening in that area. The higher the exhaust opening the better. Having the exhaust opening close to and as high up as possible to the seat of the fire minimizes the smoke damage to the structure.
-An inlet should be found opposite this exhaust opening that would allow the fans to push fresh air into the structure. The fans have to make a seal at the inlet. The fan will be set farther back then the 4 to 6 feet used when pressurizing stairwells. The
angle of the fan shroud will remain at 80 degrees. A rule of thumb is that the exhaust opening should be double the size of the opening where the PPF is placed. This will allow minimal pressure to build while permitting a large movement of air. -Contrary to stairwell pressurization (creating pressure), the objective of mechanical ventilation is to move as much fresh air as possible into the structure or area. The more fans the better. One 27” gasoline powered fan moves approximately five times more air (24,000 CFM) than our 16” electric box fan (3,400 CFM). Using roll-down doors can allow two fans to be placed side by side (parallel) blowing into a structure. A seal is created by adjusting the height of the roll-down door and the set back of the fans.
-Even if the inlet is remote from the area that we are trying to ventilate; once the fans begin to operate, the entire interior air volume will increase and begin to move to a lower pressure that will be outside of the structure.
-The wind must always be a consideration, even in this operation. If the wind is striking the face of the building that we are using as an exhaust outlet, then the efficiency of the fans will be greatly diminished. In that instance, a size up may identify other exhaust or inlet points to be used that will allow the wind to benefit the operation.
-Every structure will be different. The officer in charge of the ventilation will have to use experience and knowledge to overcome some of the complexities encountered.
9.3 Advantages of positive pressure mechanical ventilation are:
-Rapid PPF deployment results in members not having to enter and operate inside a contaminated area.
-Fans blowing fresh exterior air into the structure have shown to be 75% more efficient then negative pressure ventilation, which uses fans to pull smoke and contaminants from within a structure to the outside air. Exterior air tends to be cooler and of lower pressure than interior air which may improve interior conditions and reduce overhaul time.
9.4 Some examples where positive pressure mechanical ventilation would be beneficial include:
Subways
Sub-cellars
Theaters and auditoriums
Schools
Hospitals
Note: In all instances, the goal is to provide a higher air pressure on one side of the area to be
ventilated using a PPF, and a lower air pressure exhaust ventilation point on the opposite side. If possible using an electric box fan placed (carried by all ladder companies) inside the building/area at the exhaust point blowing outward will increase the efficiency of the positive pressure ventilation.
Negative air pressurizations uses and procedures?
10.1 Negative pressurization is the process of creating a lower pressure within the structure
utilizing the ladder company’s electric box fan. The fan shall be operated in the exhaust mode to
remove the contaminated air from the involved structure. A fresh air inlet shall be established opposite the operating fan, thereby allowing clean exterior air to enter the structure and replace the contaminated air. This operation can prove beneficial in below grade areas with limited stairwell and fresh air access.
10.2 To maximize the efficiency of this operation, the box fan should be hung in a window or doorway as high as possible. Salvage tarps should be used to create a seal around the operating fan, allowing the exhaust fan to create an area of negative pressure. When tarps are not used, churning of the interior air occurs limiting our ability to ventilate the area.
Note: An alternate method, when tarps are not available or the box fan can not be hung, is to position the fan inside the contaminated area facing the exhaust opening 6 to 8 feet back and tilted up at an angle of approximately 30 degrees. This positioning will form a seal of air around the exhaust opening preventing churning of the air and increasing efficiency.
