CVFD Training – Ventilation Practices SFFMA Training Objectives: 8-01.05 – 8-01.08 Vertical Ventilation • Opening roof/existing roof openings for allowing heated gases, smoke to escape • Firefighters must understand basic types, designs of roofs (Continued) Firefighter I 11–2 Vertical Ventilation • Firefighters must know how roofs in the response areas are constructed (Continued) Firefighter I 11–3 Vertical Ventilation — Preincident Inspections • Identify – New construction projects – Existing construction – Use of lightweight building materials – Information that can alert firefighters Firefighter I 11–4 Likelihood of Roof Collapse During Vertical Ventilation • Based on – Volume of fire – How long fire has been burning – Type of construction – Level of protection – Load on roof Firefighter I 11–5 Responsibilities During Vertical Ventilation — Officer in Charge • • • • Determine it can be done safely, effectively Consider age, type of construction Consider location, duration, extent of fire Observe safety precautions (Continued) Firefighter I 11–6 Responsibilities During Vertical Ventilation — Officer in Charge • Identify escape routes • Select place to ventilate • Move personnel, tools to roof Firefighter I 11–7 Responsibilities During Vertical Ventilation — Leader on Roof • • • • Ensure roof safe to operate on Ensure only required openings made Direct efforts to minimize secondary damage Coordinate crew’s efforts with firefighters inside building (Continued) Firefighter I 11–8 Responsibilities During Vertical Ventilation — Leader on Roof • Ensure safety of all personnel • Ensure team leaves roof as soon as assignment completed Firefighter I 11–9 Safety Precautions During Vertical Ventilation • Check wind direction with relation to exposures • Work with wind at back/side to provide protection while cutting • Note existence of roof obstructions/ excessive weight on roof (Continued) Firefighter I 11–10 Safety Precautions During Vertical Ventilation • Provide secondary means of escape for crews (Continued) Firefighter I 11–11 Safety Precautions During Vertical Ventilation • Ensure main structural components not cut while creating opening • Guard opening to prevent personnel falling into it • Evacuate roof promptly when ventilation complete (Continued) Firefighter I 11–12 Safety Precautions During Vertical Ventilation • Use lifelines, roof ladders, other means to prevent sliding/falling • Make sure roof ladder (if used) firmly secured over roof’s peak • Exercise caution when working around electric, guy wires (Continued) Firefighter I 11–13 Safety Precautions During Vertical Ventilation • Ensure all personnel on roof wear full PPE including SCBA • Keep other firefighters out of range of those swinging axes, operating saws • Caution axe users to be aware of overhead obstructions (Continued) Firefighter I 11–14 Safety Precautions During Vertical Ventilation • Start power tools on ground to ensure operation; shut off before hoisting/ carrying to roof • Extend ladders 3-5 rungs above roof line, secure ladder • When operating from aerial ladder platforms, floor of platform even with/ slightly above roof level (Continued) Firefighter I 11–15 Safety Precautions During Vertical Ventilation • Check roof for structural integrity before stepping on, continue sounding throughout operation (Continued) Firefighter I 11–16 Safety Precautions During Vertical Ventilation • Always walk on bearing walls, strongest points of roof structure • Ensure ceilings punched through to enhance ventilation Firefighter I 11–17 Unsafe Roof — Warning Signs • • • • Melting asphalt Spongy Roof Smoke coming from roof Fire coming from roof Firefighter I 11–18 DISCUSSION QUESTION What should you do if you are assigned to ventilate a roof and find warning signs present? Firefighter I 11–19 Roof Coverings • Part of roof exposed to weather • Types • Some susceptible to ignition from sparks, burning embers; others not • Some have coating of insulating material Firefighter I 11–20 Existing Roof Openings • Sometimes used for vertical ventilation • Rarely in best location/large enough • Usually supplement cut holes (Continued) Firefighter I 11–21 Existing Roof Openings • • • • • Scuttle hatches Skylights Monitors Ventilating shafts Penthouse/bulkhead doors Firefighter I 11–22 General Ventilation Considerations for Roofs • Square/rectangular opening easier to cut, easier to repair • One large opening better than several small Firefighter I 11–23 Flat Roofs • Commonly found on commercial, industrial, apartment buildings • Common on many single-family residences (Continued) Firefighter I 11–24 Flat Roofs • May/may not have slight slope for drainage • Frequently penetrated by chimneys, vent pipes, etc. • May be surrounded and/or divided by parapets (Continued) Firefighter I 11–25 Flat Roofs • May support water tanks, HVAC equipment, etc. • Structural part • Decking • Construction materials determine equipment necessary to ventilate Firefighter I 11–26 Pitched Roofs • Among most common are those elevated in center along ridge with roof deck sloping down to eaves along roof edges (Continued) Firefighter I 11–27 Pitched Roofs • Shed roofs — Pitched along one edge with deck sloping down to eaves at opposite edge • Most involve rafters/trusses • Have more pronounced downward slope than flat; may be steep (Continued) Firefighter I 11–28 Pitched Roofs • Procedures for opening similar to flat roofs; precautions must be taken to prevent slipping • Some types may require different opening techniques Firefighter I 11–29 Arched Roofs • Can span large open areas unsupported by pillars/posts • One type uses bowstring trusses (Continued) Firefighter I 11–30 Arched Roofs • Lamella or trussless arched roofs (Continued) Firefighter I 11–31 Arched Roofs • Procedures for cutting ventilation openings same as flat/pitched except no ridge to hook roof ladders; curvature of roof prevents roof ladders from lying flat Firefighter I 11–32 Precast Concrete Roofs • Can be fabricated off-site • Available in many shapes, sizes, designs (Continued) • Some use lightweight material Firefighter I 11–33 Precast Concrete Roofs • Lightweight usually finished with roofing felt and mopping of hot tar • Extremely difficult to break through • Existing openings should be used for ventilation on heavy roofs Firefighter I 11–34 Poured-In Place Concrete Roofs • Some lightweight concrete roof decks poured in place over permanent form boards, steel roof decking, paper-backed (Continued) mesh, or metal rib lath Firefighter I 11–35 Poured-In Place Concrete Roofs • Relatively easy to penetrate • Some can be penetrated with hammer-head pick or power saw with concrete blade • Heavier roofs require jackhammer/ diamond-tipped chain saw Firefighter I 11–36 Metal Roofs • Made from several different kinds of metal; constructed in many styles (Continued) Firefighter I 11–37 Metal Roofs • Light-gauge steel roof decks can be supported on steel frameworks/laid over existing roof • Light-gauge cold-formed steel sheets used primarily for industrial buildings (Continued) Firefighter I 11–38 Metal Roofs • Except when covered with lightweight concrete, seldom covered with roofing material • Metal cutting tools/power saws with metal cutting blades must be used to open (Continued) Firefighter I 11–39 Metal Roofs • Often penetrated by roof openings • Older buildings may have roofs made of large pieces of sheet metal laid over skip sheathing Firefighter I 11–40 DISCUSSION QUESTION What are some examples of occupancies in your area? How would these occupancies need to be addressed when ventilating the building? Firefighter I 11–41 Trench Ventilation (Strip Ventilation) • Used to stop spread of fire in long, narrow structure (Continued) Firefighter I 11–42 Trench Ventilation (Strip Ventilation) • Performed by cutting large opening at least 4 feet (1.2 m) wide extending from one exterior wall to opposite exterior wall • Often, large ventilation opening is cut between trench cut and fire Firefighter I 11–43 Conventional Basement Ventilation • In absence of built-in vents from basement, heat and smoke from basement fires quickly spread upward (Continued) Firefighter I 11–44 Conventional Basement Ventilation • Can be accomplished several ways – Ground-level windows — horizontal ventilation – Windows unavailable — interior vertical ventilation Firefighter I 11–45 Factors Reducing Effectiveness of Vertical Ventilation • • • • Improper use of forced ventilation Indiscriminant window breaking Fire streams directed into ventilation openings Breaking skylights (Continued) Firefighter I 11–46 Factors Reducing Effectiveness of Vertical Ventilation • Explosions • Burn-through of roof, floor, wall • Additional openings between attack team, upper ceiling Firefighter I 11–47 Negative-Pressure Ventilation (NPV) • Oldest type of mechanical forced ventilation techniques — Using fans to develop artificial circulation/enhance natural ventilation (Continued) Firefighter I 11–48 Negative-Pressure Ventilation (NPV) • Fans placed in windows, doors, roof vent openings to exhaust smoke, heat, gases (Continued) Firefighter I 11–49 Negative-Pressure Ventilation (NPV) • NPV operations – Fan should be positioned to exhaust in same direction as prevailing wind – Technique uses wind to supply fresh air – If prevailing wind too light, fans can be positioned on windward side of structure to blow air into building (Continued) Firefighter I 11–50 Negative-Pressure Ventilation (NPV) • If open areas around smoke ejector not properly sealed – Air can recirculate into building – Atmospheric pressure pushes air back through spaces; smoke reenters room – To prevent recirculation, cover area around fan (Continued) Firefighter I 11–51 Negative-Pressure Ventilation (NPV) • Flow of smoke, other gases to exit opening should be kept straight as possible (Continued) Firefighter I 11–52 Negative-Pressure Ventilation (NPV) • Avoid opening windows near exhaust fan because this can reduce efficiency • Remove all obstacles to airflow (Continued) Firefighter I 11–53 Negative-Pressure Ventilation (NPV) • Do not allow intake side of fan to become obstructed • When ventilating potentially flammable atmospheres, only exhaust fans with intrinsically safe motors, power cable connections should be used (Continued) Firefighter I 11–54 Negative-Pressure Ventilation (NPV) • Exhaust fans should be turned off when moved; carry by handles • Before starting exhaust fans, be sure no one near blades; other materials not in position to be drawn into fan • Discharge stream of air should be avoided (Continued) Firefighter I 11–55 Positive-Pressure Ventilation (PPV) • Forced ventilation technique that uses highvolume fan to create slightly higher pressure inside than that outside (Continued) Firefighter I 11–56 Positive-Pressure Ventilation (PPV) • As long as pressure higher inside building, smoke within building forced through ventilation exit opening (Continued) Firefighter I 11–57 Positive-Pressure Ventilation (PPV) • Location where PPV set up is entry point – Once location selected, create exit opening opposite – Size of exit opening varies with size of entry opening, capacity of blower – Exit opening may be window/doorway (Continued) Firefighter I 11–58 Positive-Pressure Ventilation (PPV) • Once exit opening created – Blower placed 4-10 feet (1.2-3 m) outside open entry point – Smoke then expelled from exit opening – To maintain positive pressure inside, important that no other exterior doors/ windows are opened during operation (Continued) Firefighter I 11–59 Positive-Pressure Ventilation (PPV) • By selectively opening, closing interior doors and exterior windows, it is possible to pressurize one room/area at a time (Continued) Firefighter I 11–60 Positive-Pressure Ventilation (PPV) • Several considerations for using PPV to ventilate multistory building • Requires good fireground discipline, coordination, tactics (Continued) Firefighter I 11–61 Positive-Pressure Ventilation (PPV) • Main problem in aboveground operations — Coordinating opening, closing of doors in stairwell • To control openings/pressure leaks, put one person in charge of pressurizing process (Continued) Firefighter I 11–62 Positive-Pressure Ventilation (PPV) • To ensure effective PPV operation – Take advantage of existing wind – Make certain cone of air from blower covers entire entry opening – Reduce size of area being pressurized to speed up process by selectively opening, closing interior doors (Continued) Firefighter I 11–63 Positive-Pressure Ventilation (PPV) • To ensure effective PPV operation – Keep size of exit opening in proportion to entry opening – Avoid creating horizontal openings by breaking glass/removing doors Firefighter I 11–64 Advantages of PPV Compared to NPV • Firefighters can set up PPV without entering smoke-filled environment • PPV usually effective with horizontal or vertical ventilation • Removal of smoke, heat more efficient with PPV (Continued) Firefighter I 11–65 Advantages of PPV Compared to NPV • Velocity of air currents within building minimal and minimally disturb building contents/debris • Fans powered by internal combustion engines operate more efficiently in clean, oxygen-rich atmospheres (Continued) Firefighter I 11–66 Advantages of PPV Compared to NPV • Placement of fans does not interfere with ingress/egress • Cleaning, maintenance of fans for PPV less than those for NPV • PPV effective in all types of structures (Continued) Firefighter I 11–67 Advantages of PPV Compared to NPV • Heat, smoke may be directed away from unburned areas/paths of exit with PPV • Exposed buildings can be pressurized by PPV to reduce fire spread Firefighter I 11–68 Disadvantages of PPV • Intact structure required • Interior carbon monoxide levels may be increased if exhaust from fans allowed to enter • Hidden fires may be accelerated, spread throughout building Firefighter I 11–69 DISCUSSION QUESTION In what types of fires do you think PPV would be more effective? In what types of fires will NPV work better? Firefighter I 11–70 Hydraulic Ventilation • May be used in situations where other types of forced ventilation unavailable • Used to clear room or building of smoke, heat, steam, gases after fire controlled (Continued) Firefighter I 11–71 Hydraulic Ventilation • Uses air movement created by fog stream to help draw products of combustion out of structure Firefighter I 11–72 Performing Hydraulic Ventilation • Fog stream set on wide fog pattern that covers 85-90 percent of window/door opening from which smoke will be pushed out • Nozzle tip should be at least 2 feet (0.6 m) back from opening • Larger the opening, faster the process (Continued) Firefighter I 11–73 Performing Hydraulic Ventilation Firefighter I 11–74 Disadvantages to Hydraulic Ventilation • • • • May increase amount of water damage Drain on available water supply If freezing, increase in ice on ground Firefighters operating nozzle must remain in heated, contaminated area • Operation may be interrupted when nozzle team leaves to replenish air Firefighter I 11–75 Building Systems • Many modern buildings have built-in HVAC systems • Systems can significantly contribute to spread of smoke, fire throughout structure Firefighter I 11–76 Building System Operations • Usually controlled from panel in maintenance and operations center in the building • Wherever located, often diagram of duct system and information on smoke detection, fire suppression systems built into HVAC ductwork (Continued) Firefighter I 11–77 DISCUSSION QUESTION Who should operate building systems to assist in ventilation? Firefighter I 11–78 Building System Operations • Systems designed to shut HVAC system down automatically when smoke/fire detected in ducts Firefighter I 11–79 Fire Personnel • Should be familiar with location, operation of controls allowing them to shut down HVAC system • May need to shut HVAC system down during fire; clearing system of smoke, restoring to operation responsibility of building engineer or maintenance superintendent (Continued) Firefighter I 11–80 Fire Personnel • Should check combustibles adjacent to ductwork for fire extension due to conduction Firefighter I 11–81 Smoke Control Systems • Many other buildings equipped with built-in smoke control systems • Designed to confine fire to as small an area as possible • Achieve confinement by automatic closure of doors, partitions, windows, fire dampers (Continued) Firefighter I 11–82 Smoke Control Systems • Usually have system diagram in same location as control panel; panel should indicate where alarm originated, which automatic closers activated Firefighter I 11–83