Using Backpack Leaf Blowers on Grass Fires

Tests reveal the limitations of leaf blowers as firefighting tools

By KB Hallmark
Published Sunday, September 18, 2011

Traditional engine companies have always been at a disadvantage at grass and brush fires. Most equipment, from PPE to hand tools, is designed for structural firefighting and not meant for wildland/urban interface (WUI) usage. This leaves engine crews either watching the fires burn from their pavement queens or trying to come up with new ways to fight WUI/wildland fires when away from their engines. One idea that has come up is the use of backpack leaf blowers.

After a disastrous set of New Year’s Eve fires in 2007, a local dealer loaned the Converse (Texas) Fire Department (CFD) a large backpack blower so we could evaluate it for use on grass fires. Research into previous usage only turned up a few articles, most of which discussed using the blower for clearing firelines in wooded areas, not actually attacking a fast-moving grass fire. No one was quite sure how to use it, so no one really wanted to be the first to try it. So I asked the chief if I could evaluate it for potential uses, and he readily agreed.

A Little Background
I immediately took the blower home with me. I had tried to research the idea of using the blowers before, and from what I found, it’s a pretty common practice, but not here in Texas. Shindaiwa, a power tool manufacturer, had produced a training/advertising video using one of their models. This, along with an article from Australia, was about all the guidance I had.1 (For more about Australia’s use of leaf blowers, see the sidebar below “Experience from the Driest Continent on Earth” by Shan Raffel.)

The blower we received was a RedMax EB4401. The dealer had chosen it due to its size and output. Luckily for us, he had chosen a suitable size and model that hadn’t been recalled due to accidentally catching on fire while in use. (Given our predicted usage of the product, we didn’t need any extra help in dealing with fire.)

The CFD serves a suburban area outside of San Antonio and doesn’t get many grass fires. My rural volunteer department, on the other hand, sees more grass and brush fires with greater intensity and in a variety of fuels. Taking on a flaming hayfield is a bit more intense than putting out a backyard fire.

Note: Research from the Kentucky Division of Forestry has indicated that leaf-blower air speed for this kind of work should be at least 200 mph. So before using this tactic, remember to do your homework first, and get the biggest blower you can afford.

The First Trial
My first trial with the blower came sooner than I thought it would. On Jan. 29, I came home at about 2000 HRS to find tones going off for a major grass fire in my volunteer response area. I arrived at the scene to find about five acres of grass already on fire. The grass was one to two feet high and fully cured from the weather, plus a strong front with low humidity had just moved in. So although this would be the first time I used the pack, the conditions were also probably the worst in which to use it.

I fired up the blower, threw it on my back, gunned it a couple of times and made my way up the flank. We were short on brush trucks that night, and every resource was needed. I quickly learned how to try to roll the fire back down into itself instead of fanning it further. I made progress, but soon realized there were limitations. Even in a wildland suit and gloves, the heat from the green side of the fire was so intense that I worried about the possible melting of the plastic parts, such as its fuel lines.

The grass presented its own problems, as it was thickly matted and rekindled in many places. Fences are also near-impossible to climb with this thing strapped to your back. Although the dry weight of the unit is less than 20 lbs., which is not much compared to the SCBA, trying to climb with the nozzle attached proved to be very unwieldy. At one point, I succeeded in holding the fire to an area while waiting for a brush truck to come up from the black and extinguish it. Although the initial results were encouraging, further refinement on the limits and usages were definitely needed.

More Research Needed
More time on the Internet yielded both the Roscommon Equipment Center’s  research data with minimum specifications and the Kentucky Division of Forestry’s (KDF) manual on blower usage2, which recommended very limited use of the blower on grass fires. Both manuals also listed modifications to the blowers to enhance safety and durability, and both stated that using blowers during direct fire attack is a bad idea.

The Roscommon manual specifically stated, “Power blowers are used for indirect attack ... and are generally not used for direct attack.” The KDF manual elaborated on this topic and pointed out the blowers present fuel risks, cause wind eddies that may carry sparks, dry out fuels that may rekindle and create irregular firelines, which create weak points where fires may jump. “On slow-burning cool fires with flames of three inches or less, with the wind against the fire, and with no foreseeable change in the fires’ behavior …, direct blowing-out of flames may become more feasible, but is still risky for the reasons above and so best avoided.” It’s hard to say we weren’t warned after that.

The Test Burn
We set up a test burn to get feedback from individual firefighters. All ranks, from firefighters fresh out of the academy to the chief, were present and tried the blower.

Our test was held in the morning with temperatures in the 60s. The humidity was predicted to be in the 70s with 5–10-mph winds—definitely ideal weather for a controlled test environment. Fire behavior predictions were done using BEHAVE software and indicated flame heights of one to three feet would be present. The fuel moisture was computed at 9% using the same software.

Our test site was a flat plateau overlooking an old gravel pit. We used the blower to help burn out control lines to contain the test fires. Once the site was prepared, we set test fires about 20 feet long perpendicular to the wind. Then we sent firefighters to attack up the flanks on the green side and turn into the head of the fire.

Most people felt the blower was helpful and easy to use. Some questioned the effectiveness of it while others felt the danger of having gasoline on your back was too much to deal with.

Individuals with wildland training and experience fared better than those who were used to structure work. We actually found the blower to work better in setting and directing the burns that were done before the training to create the black containment lines than the actual attack.

Parting the Fire?
One tactic that we tested was whether or not the blower could deflect the fire around a point or a firefighter. We tested this by lighting the fire upwind and having the operator keep an island in the middle clear of fire to simulate being overrun by a grass fire. One test produced flame lengths of five feet. The operator was able to part the fire around him and then step through the created pocket into the black side of the fire. This was meant to represent a true emergency situation and probably should not be repeated. I did it with my back to an already burned-over area as an escape route and a crew standing by with a hoseline ready to douse me. I don’t really want to try that again.

The Rural Test
I performed another test in foot-high grasses this time. This is more indicative of rural areas and grazed pastureland than suburban areas. The test burn was performed in the afternoon with a relative humidity of 37%. Winds were stronger, up to 15 mph this time. Predicted flame lengths were seven feet and above, preventing us from letting untrained personnel use the blower.

We demonstrated the extinguishments and also the escape tactic to  local volunteer departments that have more WUI and true grass fires than my paid department. Most of the firefighters were not impressed by the blowers’ performance in the higher and thicker fuel.

Blower Issues
The blower presents many issues that must be dealt with if it’s going to be a safe and effective tool. To hand it to an untrained and unequipped structure firefighter and send them forth would be highly irresponsible.

  • Proper PPE is a must with this tool. The work has to be done in a direct mode, on the green side of the fire. This is the hottest, smokiest and most dangerous place to be. Temperatures in this area will definitely burn exposed skin, and also weaken plastics, such as the ones found in the blower’s nozzle, fuel lines and gas tank. Embers and even fire may be sucked into the intake of the unit. Don’t ask me how I know this—let’s just say it was an eye-opener. Full wildland suits should be considered the minimum. Nomex hoods should be considered, not only for thermal protection, but to keep firefighters’ hair away from the intake. Gloves are needed, especially on the hand working the nozzle.
  • Proper training is essential with this tool. Anyone can figure out the blower, so the training needs to focus on fire behavior. Changing weather and fuel types will all produce different fire characteristics and flame lengths. Once flames are three or four feet tall, it’s too hot to work on the green side of the fire. A good understanding of fire behavior and a good size-up are mandatory for using this tool. Although it may work well on a low, creeping fire, it won’t keep up once the fire rolls out into good fuel.
  • We had originally hoped that the blower would serve as a single-person tool, but it seems that the best results require it to be accompanied by a crew. A team of three firefighters—one with the blower, one with a backpack pump and one with a tool, such as a shovel—will accomplish more in less time. The blower serves well to turn the flames, but complete extinguishment usually requires more help.
  • Communication is needed to safely use this blower. On the first fire I went to, which was at night, I had radioed the IC and told him of my intentions. But my message didn’t get passed to the hand crew, which was coming up through the black at the same time I turned the blower into the head. Needless to say, they weren’t too happy with finding themselves in the middle of a two-cycle-induced firewhirl.


Blower Mods
Some of the modifications that have been listed in the Roscommon and the KDF manuals will help make the unit safer. Replacing the shoulder straps with adjustable quick disconnect straps will allow the operator to dump the unit in case of a fuel fire or the need to run. Replacing clear fuel lines with rubber or even stainless-steel lines will help prevent fuel lines from breaking. The tubes can also be replaced with PVC pipe to prevent breaking.

A Final Word
While I wouldn’t call the unit useless, it definitely won’t be replacing a brush truck anytime soon. It worked well on fuels less than six inches in height. But to use it safely and effectively requires a heavy investment in training, PPE and good judgment on when to keep it on the truck and when to use it. There’s a strong element of risk involved in using it, therefore a lot of thought needs to be used when deploying it on the fireline.

References
1. Power Blowers as Fireline Building Tools, Roscommon Equipment Center Project 17. Northeast Forest Fire Supervisors in cooperation with Michigan’s Forest Fire Experiment Station: 1993.

2. Use of Backpack Blowers for Wildfire Suppression. Kentucky Division of Forestry: 2000.
 

Sidebar
Leaf Blowers: Experience from the Driest Continent on Earth
By Shan Raffel
Australian firefighters are accustomed to dealing with wildland fires on a vast scale. Approximately 22 million people inhabit the island continent, which covers an area of 2,941,299 square miles. The low population density, combined with the fact that Australia is the driest continent on earth, means it’s essential for people to make maximum use of the limited resources. There are many situations where “dry” firefighting tactics, such as back-burning, are the only options available.

Leaf Blower Trials
In the summer of 2000, Brisbane Station Officer Jeff Van Croonenborg began experimenting with high-powered backpack leaf blowers to “blow out” grass fires. The trials revealed that the air velocity at the discharge port of the blower was a critical factor in the ability to actually extinguish small fires. Trial and error lead us to believe that the velocity needed to be in the vicinity of 200 mph.

At that time, one of the few units that could meet that specification was the Shindaiwa EB630. It had a 3.9-hp two-stroke motor and was capable of delivering 612 cfm at a velocity of just over 200 mph. Now, there are a number of units that can exceed these specifications while keeping the unit weight to around 22 to 25 lbs.

Another critical area of concern was how the air stream was directed at the burning vegetation. It’s essential to direct the air stream at the ground on the leading edge of the flame base. This tends to pick up loose vegetation and dirt and drives them across the flame front onto the area that’s already burned.

Important: The primary application for the blowers is in situations where hand tools, such as rakes and beaters, would be the only other options. As a rule of thumb, if the flame height or intensity is greater than what you could tackle with hand tools, you should not try to use a blower. They are not a substitute for hose reels, Class A foam or CAFS. However there are some situations where blowers can take a lot of the manual labor out of preparing fire breaks, attacking small fires or patrolling control lines.

Naturally there was some hesitation in adopting the new idea, but crews quickly learned that when faced with several hours of work in a situation that demanded dry firefighting techniques, it was more effective to use a blower than to swing a beater or use a rake hoe.

Tactical Considerations
In all wildland firefighting operations, the wind speed and direction are very important in determining the best tactics and tools to be utilized. When the wind is blowing away from the property to be protected, the backpack PPV can be used at 90 degrees to the firebreak line. When the wind is parallel to the property, the angle of the air stream needs to be varied to prevent the fire from working around and behind the control line.

The most difficult situation (regardless of what tools are being employed) is when the wind is blowing toward the property being protected. In this case, it will be necessary to use just enough throttle to avoid pushing embers up high into the wind. Additional personnel will be required to ensure that there’s no spotting behind the operator.

Safety Considerations
Like any piece of firefighting equipment, it’s essential to ensure that safe working practices are adopted and that appropriate training is provided. If used inappropriately, the blower’s powerful air stream can spread or intensify the fire. The limitations of the equipment must be understood, and full wildland firefighting PPE, including eye and hearing protection, should be worn at all times.

While a skillful operator may be able to extinguish fires that are larger than what could normally be attacked with rakes and beaters, this should be avoided because of the likelihood of exposure to excessive radiant heat and reduced safety margin.

Gasoline is currently the fuel type used in blowers, which can present safety issues. All elements of the fuel system must be regularly checked to ensure there are no leaks. The harness is designed to be easily doffed, and firefighters should not hesitate to dump the equipment if they feel they are in danger.

The bottom line: High-powered backpack leaf blowers can assist in maximizing resources and reducing firefighter fatigue in situations where water supplies are limited or it’s not possible to get water to the point of operation.

 

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Leaf blowers have been used to clear firelines in wooded areas, but little research has been done on using the blowers as a means for attacking fast-moving grass fires. (AP Photo/The Charleston Gazette, Lawrence Pierce)
A firefighters uses a leaf blower to prepare a fire break in an area of dense leaf litter, which reduces the amount of manual labor that’s normally performed on this task. Photo courtesy Shan Raffel
When operating leaf blowers during grass fires, it’s essential to ensure that safe working practices are adopted and that appropriate training is provided. If used inappropriately, the blower’s powerful air stream can spread or intensify the fire. The limitations of the equipment must be understood, and full wildland firefighting PPE, including eye and hearing protection, should be worn at all times. Photo courtesy Shan Raffel
During wildland/urban interface fires, when the wind is blowing away from a property, the backpack PPV can be used at 90 degrees to the firebreak line. When the wind is parallel to the property, the angle of the air stream needs to be varied to prevent the fire from working around and behind the control line. Photo courtesy Shan Raffel


Using Backpack Leaf Blowers on Grass Fires

Tests reveal the limitations of leaf blowers as firefighting tools leaf blowers for clearing firelines
Leaf blowers have been used to clear firelines in wooded areas, but little research has been done on using the blowers as a means for attacking fast-moving grass fires. (AP Photo/The Charleston Gazette, Lawrence Pierce)

leaf blower prepares firebreak
A firefighters uses a leaf blower to prepare a fire break in an area of dense leaf litter, which reduces the amount of manual labor that’s normally performed on this task. Photo courtesy Shan Raffel

leaf blower direct attack
When operating leaf blowers during grass fires, it’s essential to ensure that safe working practices are adopted and that appropriate training is provided. If used inappropriately, the blower’s powerful air stream can spread or intensify the fire. The limitations of the equipment must be understood, and full wildland firefighting PPE, including eye and hearing protection, should be worn at all times. Photo courtesy Shan Raffel

leaf blower making direct attack
During wildland/urban interface fires, when the wind is blowing away from a property, the backpack PPV can be used at 90 degrees to the firebreak line. When the wind is parallel to the property, the angle of the air stream needs to be varied to prevent the fire from working around and behind the control line. Photo courtesy Shan Raffel

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