Master streams

Picture the charred remains of a large commercial building, or a three-storey wood-frame apartment building from which the roof has been completely burned. Typically, in these scenarios, the master stream is used as a surround-and-drown tool, and certainly, in some cases, that may actually be the best use of the stream. But there are many fires at which early water application and proper stream management will provide better outcomes.

Science has proven that a fire can double in size every 30 seconds to one minute, so it stands to reason that the earlier firefighters get an effective water stream on the fire, the better the outcome will be. Think about how long it takes to get water on target. Timing exercises have shown that suppression crews take an average of 90 seconds for handline deployment from time of arrival to water on target from the exterior at a house fire. This timespan increases significantly for an interior attack on a low- or mid-rise structure, and could take 15 minutes or longer for a highrise.

Recent studies by the National Institute of Standards and Technology (NIST) show that application from the exterior and correct stream usage improve the interior conditions of the structure. But what about the cases in which the fire cannot be accessed with a handline from the ground? Consider fires that are above the fifth floor, or have an object such as a wood or glass deck railing blocking the stream access. Three-storey, wood-frame, unsprinklered apartment buildings are common here in British Columbia. Such situations can make access with a handline challenging, if not impossible. Rapid and safe exterior water application from an aerial master stream can confine the fire, buy time to set up for a move to the interior and make a positive difference to the outcome.

Reo Jerome is a captain and acting battalion chief with the Surrey Fire Service. He agrees that timely water application can make a difference.

“Once we arrive to a fire we have a window of opportunity to get the right amount of water in the right place,” Jerome said. “Accomplishing this objective with an aerial master stream can be very challenging without prior training.”

So how long does it take to position the apparatus, stabilize and get water on target? Training officers at the Justice Institute of BC fire and safety division in Maple Ridge developed an aerial strategies and tactics course to help equip firefighters to use their aerial apparatuses to their full advantage.

“Many fire departments across Western Canada use quints, and many of them respond as the first-out apparatus with at least four firefighters on board,” Jerome said.

“Time trials have shown that once the vehicle is in position with the spring brakes applied, water can be on the target in less than three minutes, and in some cases in as little as two minutes. Our job as firefighters is to create a toolbox of tactics throughout our careers so that we can pull the appropriate tactic out if and when the opportunity presents itself. That is why we train!”

Knowing how to apply a timely and effective master stream is not as easy as one would think. Communication, aerial positioning, water supply, nozzle and pattern, and the safe use of the aerial device all come into play.

Precious time can be lost just getting the apparatus into the correct position. Landscaping, parked cars, and other emergency vehicles may all prohibit access to the best position. Both the operator and the officer need to be involved in the decision about where to best position the turntable (note the use of the word turntable versus aerial). Good communication is key.

Once the placement decision is made, best practices recommend that the truck be backed into position (rear mount) to allow for maximum reach of the aerial ladder. This also allows for a quick escape, if necessary. Developing backing hand signals that enable quick vehicle placement can be critical. In Surrey, we teach firefighters to drop a road cone in the spot where the centre of the turntable should end up, and a spotter then helps the operator to back into the location; this frees the officer to deal with more urgent matters. It sounds obvious, but effective backing and hand signals that both the spotter and operator clearly understand should be standardized and regularly practised within a department to ensure quick, effective and safe communication.

Scrub is a term that describes the amount of surface area of the structure that an aerial tip can access. If only the master stream is used at the incident, scrub is not an issue. If, however, the master stream is followed up with rescue or other access to elevated floors, then placement requires maximizing the scrub area. Whenever possible, the aerial device should be positioned at the corner of a structure to increase the scrub area; this allows access to two sides of the building and maximizes safety in the event of a collapse or falling debris. It is also important to understand the limitations of the nozzle angle on your aerial apparatus. Some nozzles are limited to 15 degrees to prevent too much side load from nozzle reaction, while others have a range of 90 degrees.

Speed is always important, and that means use of the water tank needs to be considered until a secure water source is obtained. Sometimes called an “aerial blitz attack,” this is a tactic that has been used by experienced fire-ground officers. As per NIST study recommendations, limited duration bursts of water should be used, rather than continuous water application. This prevents excess pressure in the compartment from steam production (and also prevents draining the tank in a big hurry!). A straight- or solid-stream pattern allows for deeper penetration and continuous venting of heated gases around the stream as it enters the compartment. The desired outcome is to confine the fire and make conditions more tenable for interior operations. The operator raises the pump pressure to ensure an effective stream, then opens and closes the aerial discharge valve to allow for controlled bursts from the master stream. A pressure governor should be used in RPM mode. If the pump is in pressure (PSI) mode, small pockets of air can develop, which can cause the governor to drop the engine to idle, affecting stream accuracy, penetration and reach.

Headsets are useful for communication between the pump operator on the pump platform and the aerial operator on the turntable. Often the pump operator will not be able to see the stream, so will need advice from the aerial operator to understand if the burst is reaching the target in the time patterns desired. Headsets also reduce engine and scene noise, allow for easy communication between operators, and have a calming effect. It is also extremely important that the pump operator stay at the panel to reduce the engine to idle as the tank nears empty. If the pump is allowed to run at a high RPM while dry, damage to the pump will occur.

Some aerials have remote-control devices that allow for better visibility; the user is able to aim the nozzle on the target while the aerial operator is swinging the ladder into position. This simultaneous activity can save precious time for achieving water on target.

There is debate over adjustable fog or a smooth-bore nozzles. For many years my preferred nozzle was the 1 3/4-inch smooth bore. The 800 gpm at 80 psi that this nozzle provides seemed a reasonable amount of volume  from an aerial device, and the solid stream allowed for maximum penetration. But due to gravity-feed limitations and the smaller internal piping between the tank and the pump, drawing off the tank will give only a reliable 500 gpm, no matter what the nozzle provides. So really the 1 3/8-inch nozzle tip is the way to go.

The main arguments against the adujustable fog nozzle were the plugging that can happen on long-duration incidents, and the better reach that can be achieved with a smooth-bore nozzle. But these modern nozzles are automatic, which means an internal piston and spring cause the nozzle to give the correct stream depending on the pressure applied and the water that is available. The automatic nozzle also has the variability of the straight, narrow or wide fog pattern, which could be an advantage for use as exposure protection. These nozzles have decent reach, are better for foam production and have a wide range of volume. The straight stream setting produces a stream that is pretty similar to a solid-bore stream.

If the operator has been asked to deliver a specific gallonage from a specific stream pattern, it is important to note that an eye will need to be kept on the flow meter, as the nozzle will give an effective-looking stream even if volume is low. Relay pumping is recommended for distances of 91.4 metres (300 feet) or more from a hydrant, and dual high-volume lines are recommended for a distance of less than 91.4 metres.

A master stream is a powerful tool and, if not handled properly, can destroy property and threaten lives. Never apply a master stream into the interior of a building in which there are firefighters or civilians who are not protected behind a fire barrier such as a door or firewall. The pressure created from improper stream application can cause the heated gases to move throughout the interior, which can quickly cause conditions to deteriorate.

City of Surrey Deputy Chief Larry Thomas advises aerial personnel to use caution and train ahead of time if early use of the master stream is to be considered.

“Commercial and multi-residential building fire rates in Surrey are steadily declining as the city grows,” Thomas said. “The challenge for fire services in the future is how to maintain the tactical fire suppression skill sets among its staff (of more than 350 in Surrey).

“Tactics such as this should not be broadly applied without ensuring all fire officers and their crews have a thorough understanding of the fire dynamics, building construction and occupant status. Although using master streams from an aerial device can be very effective in certain situations, they can be equally dangerous if applied by someone without the pre-requisite knowledge of what and why they are selecting this tactic. In cities or towns with lots of non-fire protected commercial and multi residential building stock, the aerial master stream application – utilized as an initial attack tactic – should be a tool given consideration.”

Another safety consideration is the weight of the water being applied. A gallon of water weighs about 4.5 kilograms (10 pounds). A flow rate of 800 gpm for 10 minutes is equivalent to 3,629 kg (8,000 pounds) a minute – that’s more than two full-size pick-up trucks every minute! If you have been flowing the master stream for long periods of time with no positive effect on the fire, and you do not see the water exiting the building, a lot of weight is sitting somewhere, shut it down.

“Officers in charge of aerial apparatuses need to inform and empower their operators to move or shut off the stream if it is not hitting the desired target – just like we do with a handline”, Jerome said.

Aerial master streams can be effective tools at major incidents to confine fires and make conditions better for fire crews; they do not need to be simply a surround-and-drown tool. Through training and practise with master streams, fire crews learn to recognize the need for a master stream, and use it effectively to minimize property damage and reduce risk to firefighters and civilians.

Acting Capt. Dave Baird has worked in the suppression division of the Surrey Fire Service for more than 21 years. He also instructs for the Justice Institute of BC. In 2012 and 2013 he was a committee member for the validation of the IFSTA Aerial Operators Handbook. He can be reached at DCBaird@surrey.ca