SMOKE CONTROL USING POSITIVE PRESSURE FANS

Transcription

1 SMOKE CONTROL USING POSITIVE PRESSURE FANS 1. INTRODUCTION 1.1 This circular outlines operational guidelines for smoke and CO control using positive pressure fans (PPF) at fires and emergencies. 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. The Department has done extensive research and testing on positive pressure ventilation to provide the Incident Commander (IC) ways of conducting a safer operation for firefighters and civilians. 2. SCIENCE OF AIR MOVEMENT 2.1 The natural tendency of air is to move from a higher pressure area to a lower pressure area. As a fire develops and heat increases, the fire will pressurize the area that it occupies. This higher pressure will move towards a lower pressure area that may be in other parts of the structure or other ventilation openings. PPFs are used to mechanically create areas of a slightly higher pressure to contain fire gases and control the flow path of smoke and convection currents that otherwise would be free to move throughout the structure, endangering civilians and firefighters. 3. DEPLOYMENT 3.1 High Rise units in Manhattan (Engines 3 and 39) carry two PPFs each. The following Ladder Companies are assigned two fans each to be carried on their assigned second piece: Ladder Companies 17, 23, 33, 51, 58, 80, 87, 105, 115, 119, 124, 142, 159, 160, 172. These PPF equipped units shall be dispatched on a signal or these units can be special called as needed by an IC. 3.2 These ladder companies are designated Ventilation Support Group Companies and are responsible for deploying and operating PPFs when ordered by the IC. 4. EQUIPMENT 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. 4.2 Any other equipment deemed necessary. 1 Rev. 01/23/14

2 5. RESEARCH ON STAIRWELL PRESSURIZATION 5.1 In February 2008, the FDNY conducted studies on stairwell pressurization in FPMDs. The information gained from these studies was similar to what was learned in commercial building fire tests conducted more than thirty years ago by Commissioner John T. O Hagan. Local law #5 of 1973 and NFPA 92A s pressurization components were the direct result of that research. These tests have found that pressurization creates an area of safety in the stairwells for both firefighters and civilians. The technological advancements in gasoline engine performance and fan blade design, have allowed the Fire Service to utilize this equipment in a portable application, to pressurize buildings that do not have stairwell positive pressure fixed systems installed. 5.2 The FDNY has conducted numerous live fire tests that have substantiated the concept of stairwell pressurization and this concept was further tested in the field during the Pilot Program on Stairwell Pressurization. 5.3 This bulletin is based on extensive research conducted by the National Institute of Standards and Technology (NIST) and NYU Poly Tech in coordination with the FDNY, pertaining to the use of positive pressure ventilation and the pressurization of stairwells. 6. GENERAL OPERATIONS 6.1 The unit assigned to respond with the PPFs to the incident location shall be designated the Ventilation Support Group. 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. 6.2 The IC shall designate the fire attack and evacuation stairwells based on the size-up received from the first arriving engine/truck officers. The attack stairwell designation shall be announced to all members on scene over the primary tactical handie-talkie channel. This information shall also be transmitted to the Borough Dispatcher so it can be relayed to all responding units. 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. The PPFs may arrive after the fire has been knocked down or extinguished. Depending on the remaining smoke and heat conditions, removing smoke and CO may become a priority. PPFs can be used to exhaust these contaminates to the exterior. 6.3 The ventilation support group supervisor shall inform the IC of the recommended placement of the PPFs. Proper placement is based on the number of PPFs and personnel available, the location of the fire floor, number of floors in the building and the stage of firefighting operations. When fans are in position, the IC shall be notified. Stairwell pressurization will not be initiated until authorized by the Incident Commander. All members shall be notified that PPF operations are commencing. Communication with all units shall be maintained during the pressurization operation. 2

3 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. The IC must be notified when the fans have been deactivated and the stairwell doors are secured. Due to the noise created by the PPFs, handie-talkie headsets (Dave Clarke system) shall be utilized by members operating the fans to maintain communications. 6.5 The priority order for the use of PPFs is as follows: 1. Pressurizing the attack stairwell to support the fire attack, by controlling the smoke condition at the attack stair doorway and throughout the attack stairway. 2. Pressurizing the evacuation stairwell for smoke and CO control. 3. Ventilating the public hallways for smoke and CO control. 7. POSITIVE PRESSURE VENTILATION 7.1 Pressurization of the attack stairway is most effective if done simultaneously with the fire attack. The benefits of positive pressure ventilation are: Provide a safer environment for units operating or searching above the fire area. Increase visibility, permitting quicker searches of the attack stairway and will greatly improve all operations conducted in these stairways. Reduce the amount of time members are on-air when searching, completing standpipe operations and stretching hand line(s). Provide an uncontaminated area of refuge for members. Limit the spread of contaminates throughout the building. Increase visibility of the fire floor hallway in some conditions. 7.2 The ability of the fans to produce positive pressure relies on proper fan placement to create a seal and push air into the stairwell. Pushing fresh air into the area that needs to be pressurized or ventilated is the preferred method of positive pressure ventilation. 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. Placing the fan in the stairwell does not create any pressure in the stairwell. It may create higher CO levels and negative stack effect by pulling smoke and heat down the stairwell. 3

4 7.3 Ventilation support group supervisor shall supervise the placement of fans. The ground floor shall be the initial location for rapid deployment; however, the following variables should be considered when choosing that location: The operation of the PPFs can create considerable noise which may interfere with the Incident Command Post, if the ICP is located in the lobby. If this is the case, look for another location other than the lobby entrance to the attack stairwell. Some residential buildings may have one or more stairwells that terminate on the exterior of the building. Utilizing an exterior door provides the added benefits of reduced noise and CO levels in the building. Note: In project type multiple dwelling fires, the ICP is usually not located in the lobby. Often in project type multiple dwellings the ICP is located outside the building with a view of the fire building, and PPF noise should not hamper communications. The pressure delivered to the attack stair by the PPF will be great enough to allow for up to three stairwell doors to be open and pressurization to remain effective. However, all members should understand that keeping as many doors closed as possible is the goal. Members are permitted to move from one area to another as long as they remember to close the stairwell door behind them. When units are committed before fan activation and a line is stretched through a stairwell door, the door should be closed as much as possible to maintain positive pressure. Note: Maintaining a proper stairwell seal is the responsibility of all members on the fireground. Any ventilation or open doors will create air movement that can negatively effect operations on the fire floor, floors above and below. Doorways may be accessed; however, they must be maintained closed as much as possible. The ventilation support group supervisor shall instruct ventilation group members to survey the attack stairs below the fire floor to verify that doors in the stair enclosure are maintained closed, unless operating hoselines are stretched through the door. The ventilation support group supervisor shall request that the IC instruct the 3rd and 4th ladder companies operating above the fire floor, to verify that doors in the stair enclosure are maintained closed. 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. Note: In buildings over 40 stories in height, the IC should consider special calling an additional ventilation support group. The extra fans can be used to augment pressures in the stairwell. 4

5 7.4 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: 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. 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. 7.7 The benefits of pressurizing and clearing contaminated stairwells of smoke and CO are: Facilitate the rapid and efficient evacuation and searches of the stairwells. Limit the contamination of other parts of the structure. Reduce the calls from panicked residents due to smoke. It provides fresh air to operating units. 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. 5

6 7.8 At times, units may encounter elevated CO levels due to operating fans. The use of exhaust hoses will help to reduce CO levels in the building created by these fans. It is recommended that units use their CO meters to monitor levels at all times. If high levels of CO are encountered at any time, the IC must be notified. Members operating on the fireground shall make full use of all their PPE. 8. SEQUENTIAL VENTILATION 8.1 After fire extinguishment, the products of combustion can be ventilated vertically through the attack stair. This is accomplished by placing a fan at the base of the evacuation stairwell, and pressurizing that stairwell. This procedure will create an area of high pressure in the evacuation stairwell and utilize the area of lower pressure in the attack stairwell to facilitate smoke removal. The evacuation stairwell will be contamination free for this type of ventilation. Note: Placement of the fan for sequential ventilation shall be on the exterior of the building with exhaust hoses in place. The goal of sequential ventilation is to replace the smoke and CO in the building with fresh air. Placement of a gas powered fan inside a building during sequential ventilation would negate the benefits of the operation. 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. 6

7 9. 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 follows: 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. 7

8 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. 10. NEGATIVE PRESSURIZATION 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 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. 11. SAFETY 11.1 The fan is a highly mobile unit. There are two wheels mounted to the front of the fan shroud and a collapsible handrail for transport with a minimal profile The PPF shall never be transported while in operation. If the need arises to move the fan, it shall be shut down before transportation Due to the high operating RPMs and thrust created, severe injury to the operator and damage to the fan could result if the blades contact the fan shroud or if the fan were to topple over. 8

9 11.4 Limit the time that members are directly in front of an operating fan. Debris shall be cleared from the vicinity of the fan prior to fan activation. Debris not cleared from the area of an operating fan can be picked up and discharged at a high rate of speed from the front of the fan. Eye and ear protection shall be worn whenever the fan is operating PPFs should be lifted by two members whenever the fans need to come off the ground, e.g., on and off apparatus, up stairs. PPFs are heavy pieces of equipment. Damage to the fan and injury to the member could result Fans shall never be refueled inside a structure. The possibility of the gasoline coming in contact with a hot exhaust manifold could result in a fire. If the fan needs to be refueled at an extended operation, it shall be shut down and moved to an outside area remote from any foot traffic. This remote area is necessary to assure safety as well as to not contaminate the fire area with what could be detected as an accelerant Fans should be inspected and started daily at the beginning of the 9x6 tour. Weekly at MUD, fans shall be started and allowed to run at full RPM for 5 minutes. A visual inspection of the fan belt and tightness check should be conducted at this time. If the fans need to be serviced or repaired contact Technical Services When running fans at an incident, exhaust hoses must always be attached to the operating fan in order to limit and control the introduction of CO inside the structure. 9