BY RICHARD E. ANDERSEN
Many fire departments use positive pressure ventilation (PPV) on the fireground. There are a variety of devices available to maximize mechanical ventilation capabilities. Manufacturers currently offer an assortment of fans with gasoline or electric power and airflow capacities of up to 30,000 cubic feet of air per minute (cfm). Other options include pneumatic wheels and folding handles for easy mobility, tilt mechanisms for proper air cone placement, and exhaust extensions for gasoline models to move engine exhaust gases away from the fan intake, thereby introducing cleaner replacement air into a structure.
The typical procedure for PPV is to move the fan to the fire attack entry point, (usually the front door), start the fan, and adjust the angle to pressurize the interior. When PPV is used after the fire is under control, time is less of a concern. However, prompt ventilation more effectively addresses property conservation and should begin as soon as possible after knockdown.
The 16-inch electric smoke ejector provides mechanical ventilation in its simplest form. It moves 5,000 cfm; weighs under 50 pounds; and is compact, measuring approximately 20 inches wide by 20 inches high by 15 inches deep. With a few simple modifications, the 16-inch electric smoke ejector can become an effective part of ventilation operations and a valuable complement to the fans specifically designed and well-suited for PPV.
 Photos by author. |
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The ability to tilt the fan to the desired angle for proper air cone placement is essential when using any fan for PPV. If the fan does not include a tilting mechanism, some other method of adjustment must be improvised. Bricks, door chocks, or a set of irons (certainly more valuable elsewhere) may be used to angle the fan properly.
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A simple modification to expedite setup is to fasten a spacer to the fan frame permanently. This can be a piece of aluminum or steel angle or a piece of scrap rub rail recycled from a fire apparatus tailboard. This is secured to the top of the fan body close to the exhaust side of the fan. C-shaped cutouts at each end of the web portion facilitate cord storage (photo 1). Simply inverting the fan tilts it back about 10° to the appropriate angle for effective air cone placement (photo 2). This avoids ineffective and time-consuming fireground improvisation.
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Fast and efficient PPV depends on beginning the mechanical ventilation process as soon after arrival as is practical. An apparatus-mounted generator powers the fan; to expedite setup, a 25-foot cord with a twist-lock plug can be hardwired to the fan and stored on the spacer. An additional 25-foot extension cord can be stored with the device by coiling and placing it on the fan body (photo 3). A cord reel preconnected to the apparatus-mounted generator is useful when the setup location is more than 50 feet from the apparatus.
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To use the modified fan, move it with a preconnected cord reel and junction box to the attack point. Remove the cord from the spacer, and plug it into the junction box. Turn the fan over onto the spacer. This tilts the fan back, setting an acceptable angle for air cone placement. At a response for a furnace malfunction, the fan was placed for PPV at a door on the A side. Inside the hallway, the door to the basement was open, and the exhaust opening was a basement window on the C side (photo 4).
With these modifications, the 16-inch electric smoke ejector can be a useful and effective component of your PPV operations. In its modified form, it still fits easily into a pumper compartment and is lightweight so it can be easily and quickly removed from the apparatus and placed in operation.
The modified electric fan serves an important role in mechanical ventilation, particularly when noise or exhaust gases are a concern. Carbon monoxide calls, smoke from cooking, and oil-burner malfunctions are examples of incidents for which electric PPV is an appropriate tactic. These typical applications require that the occupancy be ventilated without introducing additional CO.
A variety of PPV equipment is available to address your apparatus storage and fire operation needs. State-of-art PPV fans now include high-efficiency fan blades and shroud assembly designs, lightweight materials, and powerful engines that move more than 25,000 cfm. The equipment specifically designed for PPV is the most effective equipment available for this purpose and is best suited to perform PPV. If your department uses PPV, you must have the proper equipment.
More than likely, your fire department still has one or more 16-inch electric smoke ejectors. With some simple and inexpensive modifications, they can become a valuable complement to your contemporary mechanical ventilation equipment and an effective tool for your PPV operations. At those incidents where ventilation must be effected without introducing CO and exhaust gases into the occupancy, the electric PPV fan is the preferred method.
RICHARD E. ANDERSEN, a 29-year veteran of the fire service, is a lieutenant and municipal training officer for the Arlington Fire District, a combination department in mid-Hudson Valley in New York State. Andersen holds a bachelor of science degree in fire service management from Empire State College, is a nationally certified fire service instructor II, and is an adjunct instructor at the New York State Academy of Fire Science in Montour Falls.
