Smoke Generators

Feb. 26, 2011

"We don't fight as many fires as we used to and that makes it difficult for our newer firefighters to learn through experience." This statement echoes through many firehouses and often goes along with discussions on the increased importance of good training to provide firefighters with the experience they used to get on the job. While the number of working fires in many areas has been reduced through effective fire prevention efforts, the overall responses have grown as departments take on additional responsibilities from EMS to handling utility emergencies to inspection services.

Now more than ever, instructors are charged with finding tools and techniques to create realistic conditions that challenge firefighters to hone their skills and do so in a timely and cost-effective way. Smoke generators have become popular training aids due to their ability to efficiently and easily create smoke conditions for training exercises. There are a number of smoke generators available to fire departments with varied designs offering a wide range of smoke output and smoke properties. For the sake of discussion, we will first review the training opportunities possible with smoke generators, followed by smoke generator operation and the characteristics and capabilities available.

Smoke generators are commonly used to add the challenge of low visibility to drills such as search and rescue and mask confidence. More advanced drills such as rapid intervention or thermal imaging techniques can also make use of smoke generators to add non-hazardous smoke to the exercise.

Training Opportunities

The most basic use of smoke generators is to produce the smoke needed to obscure vision while firefighters focus on developing one or two specific skills. Smoke generators can also provide a safe introduction to low-visibility operations for new firefighters. If a new firefighter panics and pulls off his or her mask in training smoke, it's a learning opportunity instead of an emergency.

As smoke generator options and capabilities have improved, so have their abilities to contribute to more advanced training scenarios. Because smoke generators can now continuously produce dense smoke in similar volumes to actual structure fires, they can be used to simulate these conditions in coordinated fire attack drills.

To create a room-and-contents fire scenario, a continuous operation smoke generator can be placed at the "seat of the fire." As crews arrive on the scene, the elements of size-up related to smoke conditions should be the location and amount of smoke showing, wind direction and possible ventilation tactics. Just as in a real fire, the more time taken to vent the structure, the more difficult conditions will be for crews inside. As crews enter the structure, perform primary search, find the seat of the fire and coordinate their attack with exterior vent teams, the smoke continues to bank down. When water is applied to the simulated fire, a smoke boost feature, if available, can be used to replicate thermal unbalance and associated reduced visibility. Once the instructor is satisfied that the simulated fire has been extinguished, the smoke generator can be shut down and crews can hydraulically vent, set up PPV fans, clear the structure and conduct their secondary search.

Smoke generators also let instructors create realistic fire conditions for drills in high-risk buildings. Recently, we had the opportunity to participate in a multi-agency response drill set in a local high school. The instructors' goal was to test the agencies' ability to respond to a smoky, low-heat fire condition throughout several wings of the school.

After a continuous-operation smoke generator was activated in each wing, responders were called in for a structure fire response. Crews were not briefed on the exact scenario they would be faced with, but were instead challenged to properly size-up the incident and take action. The fire department crews were divided into search-and-rescue and fire suppression teams. Closely monitored by instructors, the search team entered the building with thermal imaging cameras. Due to the density of the smoke, the firefighters had to hold the thermal imaging cameras directly to their facepieces in order to see the screens. The fire suppression team experienced similar difficulties advancing dry hose through the building.

Rescues of training manikin "victims" were quickly made and the seat of the fire was discovered, but the large area and dense smoke proved to be a challenge for crews and the time required to conduct these operations was longer than expected. A few firefighters became disoriented and separated from the team during the exercise.

In addition to the experience gained by the firefighters in large-area search, thermal imaging techniques and long hoseline stretches, they were able to test their own ability to respond to a high-occupancy building in their district. By reviewing the lessons learned in the critique, the participants gained insight that will help if ever faced with an emergency at this or a similar location. Instructors were also able to gauge the strengths and weaknesses of the response, which will be used to shape future training programs.

Although most drills conducted with smoke generators are based around structural firefighting tactics, training does not need to be restricted to indoor usage. Brought outdoors, smoke generators can also set the scene for hazmat incidents, motor vehicle accidents and CBRNE (chemical, biological, radiological, nuclear and explosives) training exercises.

All water-based smoke machines operate under the same basic concept: smoke liquid, which is primarily a mixture of deionized water and various glycol-based compounds, is pumped through a heater, vaporized into smoke and forced out of the machine. However, there are a number of factors that determine the properties and quality of the smoke. A major variable is the temperature at which the smoke is vaporized. When the heater temperature is maintained at the optimal temperature for the smoke liquid used, the resulting smoke has a more uniform particle size and temperature. The more uniform the particle size, the denser the smoke; the more uniform the temperature, the longer the hang-time of the smoke. In simpler terms, precisely controlling the temperature results in a more uniform, heavier, denser smoke that is generally more like structure fire smoke than "fog."

If smoke is produced below the optimal temperature, the smoke liquid may not be fully vaporized, resulting in "wet" smoke that is more likely to leave a residue. Smoke produced above the optimal temperature results in burnt particles, which reduces the density of the smoke and reduces the efficiency of the machine by using more smoke liquid to achieve the same low-visibility conditions.

In more basic smoke machines, as the heat energy is transferred from the heaters to the smoke liquid, the heaters inevitably cool down. Once below a certain temperature smoke can no longer be generated, which is why these machines need time to reheat and recharge between discharges. To measure heater temperature, these machines use two thermostats: one to signal when the heater has reached its high-temperature setting and the other to signal when the heaters have reached the low-temperature setting and need to reheat. When the low-temperature setting is reached, smoke production is stopped until the heaters recover and trigger the high-temperature thermostat.

More advanced smoke generators can continuously produce smoke by replacing the two-thermostat system with a temperature-control system that balances smoke liquid delivery with heater temperature. By continuously monitoring temperature, these smoke generators can increase or decrease the amount of liquid pumped to the heater so optimal smoke vaporization is achieved. If the heater temperature measures slightly above the optimal temperature, the smoke generator can increase the liquid delivered to the heaters or reduce the power supplied to the heaters. If the heater temperature begins to dip, the power supplied to the heaters is increased and/or the liquid pumped to the heaters is reduced. The result is a balance of heat capacity and liquid delivery that continuously produces smoke. Further, the smoke is produced at a more specific, consistent temperature, which improves uniformity of particle size and smoke temperature, instead of throughout a range of temperatures.

Other Factors

All smoke generators require some maintenance. Machines with higher-end internal components can be flushed with deionized water periodically to maintain efficient operation. Lower-grade machines need to be disassembled and cleaned by hand. Be sure to check the maintenance requirements and intervals before deciding on a machine.

There are also programmable options available on higher-end smoke generators. In addition to running continuously, the smoke generator can be set to run for five minutes and then turn off or run for 30 seconds every minute. Other options include wired and wireless remotes, smoke-density settings and even smoke-liquid tank-level gauges.

Features and options are available as well as a range of quality in smoke generators on the market. Understanding the options and pairing features with the needs of your training program will not only help you choose the right smoke generator, but can provide additional training opportunities to prepare your firefighters.

RYAN O'DONNELL is co-founder and chief executive officer of BullEx Digital Safety. He has founded two award-winning companies providing fire and life-safety products and services worldwide. O'Donnell draws from his experience in the fire service, where he was a decorated chief officer responsible for developing fire prevention programs, overseeing training operations and acting as incident commander at emergency scenes. He holds numerous certificates from the National Fire Academy and New York State Academy of Fire Science.

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