Proper Use Of Deck Guns

As your apparatus leaves quarters, you can see the massive cloud of boiling smoke swirl skyward. The dispatcher advises all units that multiple calls are being received reporting a working fire at a row of townhouses under construction.

Arriving only minutes after the alarm, you are astounded at how far the fire has advanced. Already, four apartments are fully involved, fire not only out every window and door but covering every wall surface and roof. A slight breeze is blowing toward rows upon rows of other wood-frame apartments in various stages of construction, yet there are still eight more units of apartments attached to the burning ones, with fire undoubtedly spreading along through the cockloft beneath the roof. And here you are arriving first due!

Photo by John Norman
The deck gun is very useful for knocking down large exterior fires where the line of sight is clear.

The advanced fire on arrival, particularly exterior fire, is the made-to-order situation for a pre-connected master stream device, the deck gun. Unfortunately, when I arrived at the scenario described above over 26 years ago, the "attack pumper" was outfitted with multiple 1 1/2-inch handlines but no deck gun, nor for that matter even a 2 1/2-inch pre-connect. The fire roared right past the puny streams from the pre-connects as ladder pipes and portable master streams were ultimately brought into play. Had a pre-connected stream of say 500 gpm been immediately available, however, it is likely that the fire would have been confined to an area less than half the total of 36 units destroyed.

The pre-connected master stream device, particularly when coupled with a bed of large-diameter supply hose or other method of sustaining a high-volume attack, is a tremendous fire attack weapon, although one that is not often used. It is not used often for two reasons: the low percentage of fires that reach very advanced stages and the lack of knowledge and experience in how to use it properly.

Since most of the fires in this country involve one- and two-family dwellings, the deck gun is rarely required; the private house just does not produce enough fire on its exterior to demand 500 gpm or more to knock down...usually. The exception involves wood-frame homes that are covered with combustible siding and spaced close together. In this case, fire venting from a lower-floor window of the fire building will quickly spread up the exterior of both buildings, extending into the upper floors of each with lightning speed through windows and attic eaves. A strong handline could knock this fire down but the deck gun is probably a better choice. It can quickly sweep along the eaves lines with its stream, the excess water cascading down the burning side, extinguishing the entire area in under 30 seconds. The big advantages of this device for this use is its speed (it can be employed off the booster tank as soon as the pumps are engaged) and its minimal manpower requirements (only one person is needed for this task; the engine chauffeur can often do it alone.) Remember, the fire is still burning inside the original fire building. The rest of the first-due engine crew should be stretching a pre-connected 1 3/4-inch handline to operate inside the house.

Fixed master streams are very useful for knocking down large exterior fires such as those in lumber yards, rows of stacked boats in winter storage at marinas and other open areas where there is a clear line of sight from the deck gun to large areas of flame. The deck gun may also be very useful at interior fires when properly positioned and used but it does have its limitations. Deck guns are not very useful at residential fires, even those that are fully involved with fire showing from every window, unless the building is threatening exposures. The reason is the design of the home and the placement of the apparatus. Due to home setbacks from the street (sidewalk and front yard), the deck gun is likely going to be at least 30 feet from the building. Houses are built with relatively small window areas, typically 30 inches wide by 40-48 inches high. Water extinguishes best by landing on and cooling the surface of burning Class A fuels. As a result, when a deck gun is applied to a house fire, it extinguishes only what is directly in line with the window opening, a 2 1/2-by-four-foot area out of a room that is approximately 10 feet by eight feet. The rest of the area on the sides of the windows continues to burn with little effect from the massive attack on the small area in line with the window. (That highlights one of the greatest advantages of another type of master stream, the tower ladder.)

Photo by John Norman
The best use of the deck gun on interior fires is on first- and second-floor fires with the apparatus placed 25 to 30 feet from the building.

Deck guns can be very useful at advanced fires inside one particular type of occupancy, the ground-floor store. The typical store fire in a "taxpayer" or strip mall is one of the best applications for the deck gun. They can develop the heavy body of fire that calls for a high water flow, and the geometric arrangement is helpful as well a 20-foot-wide storefront that is nearly all glass show windows and door. A deck gun spotted in line with the middle of the store can drive a heavy stream deep into the store hitting most, if not all, of the contents.

Apparatus positioning and apparatus design are crucial to the successful use of a fixed master stream. The stream must have a direct line of sight to its objective. Some of the apparatus built lately do not recognize the importance of the deck gun, they have the gun stuck down in a slot between the raised roof cab and the extra high side hose body, so that the gun can be used only at a 90-degree angle to the truck or at a very high angle over the cab or body. This is very inefficient. As I have mentioned, the ground-floor store, the lumber yard and the rows of buildings under construction are all prime targets for a deck gun, and all are at low angles. In addition, stream penetration is greatest at low angles, 30 percent or less; at angles of over 45 degrees, the stream strikes the ceiling right inside the windows and falls to the floor without reaching the back of the structure.

This fact affects the apparatus positioning. The best use of the deck gun on interior fires is on first- and second-floor fires with the apparatus spotted rather close to the building, within approximately 25-30 feet. If it is necessary to drive a stream into the third or higher floor, the apparatus will have to be placed farther back from the building to maintain the 30-degree angle. The farther back from the building the rig moves, the less effective the stream becomes, since its velocity decreases, it loses volume as spray breaks off and there is less opportunity to hit off to the sides of windows.

That does not mean that the deck gun is useless above the second floor. Its limitations must be complied with, however, if it is going to be beneficial. Two very important uses on upper floors are to protect occupants trapped above the fire on fire escapes and to prevent auto exposure or lapping into the floor above the fire. In these situations, the deck gun can be very effective up to the sixth or seventh floor, since the desired effect is to basically seal off the window from which the fire is venting, and not to achieve very deep penetration. In fact, deep penetration under these circumstances is likely to be undesirable since there is a strong probability of civilians or fire department members attempting access or egress within the building. An outside stream being driven into the windows will drive heat, smoke and possibly flame at these people. A very sharp stream angle to the face of the building reduces this danger by keeping the stream nearly parallel to the building instead of driving it inside.

Positioning for use of the fixed master stream must take into account several variables: wind direction, fire location, exposure considerations, street width, what the objective is in using the device (exposure protection, covering a life hazard or extinguishment) as well as the available access points. When street or other conditions prevent optimum positioning to achieve the narrow angles of stream attack described above, it may still be possible to protect people on fire escapes or aerial ladders by driving the stream onto the spandrel wall, the wall above the window that is venting fire, and let the resulting spray keep the flame away from the victims, or prevent the auto exposure.

Especially during fire attack, the precise control of this stream then becomes critical. If the stream is allowed to drop down into the window, the attack team will take a terrible pounding. Be careful! The same is true when the decision is made to switch from offensive attack to a defensive mode. All members must be withdrawn to a safe area prior to dumping a deck gun or other master stream into an area where people were operating. Even in this day when radios have improved fireground communications, some people just don't get the message. Therefore, the operators of all master stream devices must be certain to sweep the stream across any window opening without stopping when first putting the deck gun or tower ladder streams to work. This should alert anyone still pushing in with handlines that they had better get to safety, without barbecuing them. After a few moments, the stream can then be directed into the desired windows themselves.

A few words of caution are in order. These devices are extremely powerful. A two-inch tip operating at 80 psi can cause structural damage to wood and masonry bearing walls, particularly at close range. This could knock parts of the building off onto anyone who is on the side of the building opposite the stream. It may even be enough to precipitate structural collapse. In addition, a 1,000-gpm stream is putting nearly four tons of water per minute into the building. This weight can also cause a building to collapse.

Many times the deck gun has been used successfully for a brief "blitz" attack just to knock down heavy fire, and then shut down when the situations is such that a handline is ready to take over. That is an excellent tactic that works well when coordination exists on the fireground. At times, however, it seems that once master stream operations have begun, it takes an "act of Congress" to get them shut down. The incident or sector commander must have contact with and control over the pump operators supplying water to any master stream, and use it to accomplish his tactical goals. Once these goals are achieved i.e., the fire is knocked down shut down the heavy artillery!

Be very careful about sending firefighters back in to overhaul or search inside a building where master streams have been operating for long periods. Keep in mind the power that these devices can deliver. If you are dumping in excess of 500 gpm into an area and the fire is not knocked down in under a minute, something is wrong. Either you are not hitting the seat of the fire, or else you have a tremendous volume of fire, or you have a pressure-fed flammable liquid or gas fire. In any case, be very cautious before you now elect to send firefighters with handlines into this area , they may encounter a situation they cannot safely deal with. In reality, if several deck guns or other master streams are called into play for any length of time, the fire has probably entered the public relations phase anyway.

John Norman, a Firehouse® contributing editor, is a captain with the FDNY, assigned to Rescue Company 1 in Man-hattan. He is also an instructor at the Nassau County, NY, Fire Service Academy and lectures nationally on fire and rescue topics. Norman is the author of Fire Officer's Handbook of Tactics, which may be ordered by calling 800-752-9768.