Chipper Accidents are more Common than Reported

By John Ball, CTSP, and Donald F. Blair

Every time someone has the misfortune to be killed in an accident involving a wood chipper, the reporting newspaper will often include the following citation: “A total of 31 people died in chipper accidents between 1992 and 2002 according to an article published in a 2005 Journal of the American Medical Association.” Ironically, one newspaper used this phrasing twice in an eight-month period. If there have only been 31 fatal accidents in an 11 year period, it does seem odd that a single community would experience two within a year.

Once and for all, we want to set the record straight about the realities of fatal and nonfatal chipper accidents in professional tree care. Before we go into detail regarding the oft-quoted citation, a brief review of the history and classification of brush and wood chippers is in order.

There are two main classifications of the mobile brush and wood chippers commonly used in tree care maintenance: drum and disc. Drum chippers were first introduced in the late 1940s-early 1950s. Originally considered expensive when compared to dump fees for brush; most early chippers were purchased by line clearance firms, municipalities and larger residential/commercial tree services. By the mid-1980s, with a steady supply of used chippers making their way to the market while dump fees doubled and quadrupled, brush chippers became as commonplace on the job as a chain saw.

Drum chippers are manually fed by carefully aiming the butt of a limb at the throat of the spinning drum. When all goes well, the blades snatch the limb, hurling chips out the discharge chute. If the aim is off, the blades are dull or the branch is too large, too dead or any combination of the above, the chipper will either fail to feed, or will kick back what it won’t take. Feeding a drum chipper is an art. Knowing what size of what species of tree a given machine can digest; stacking the brush for “easy’ feeding and cutting off side limbs that could prevent the brush from going through, takes time and practice to achieve proficiency. In the heyday of drum chippers, the most common hazards were getting slapped with long, whippy limbs, breathing dust from something like sycamore, and kickbacks.

With all of this in mind, one of the great selling points of the disc chipper design when it was first introduced in 1980 was the fact that the hydraulic in-feed rollers took all of the skill out of chipping brush. Instead of being skilled in operating a drum chipper safely and efficiently: with a disc chipper all you have to do is stick the limb between those hydraulic rollers and the machine will do the rest. That seems simple enough, doesn’t it?

At the same time, the manufacturer assured us that this type of machine, with its automatic in-feed rollers, was so much safer than drum chippers that accidents would be virtually eliminated. Looking at the hydraulic in-feed rollers only a foot or so off the ground and less than a foot from the lip of the feed table, we were openly skeptical then and only more so now. Any piece of machinery with moving parts, lots of horsepower and sharp blades is no safer than the operator. In turn, the operator is no safer than their mindset, training, supervision and enforcement by their employer of all applicable safety and operating instructions.

In the mid-1980s, two drum chipper fatalities, in the same year within 200 miles of each other, shocked every arborist who heard about them. At the time, we thought that this was a rare and tragic coincidence by virtue of the fact that we had heard of so few such other accidents.

Not long after disc chippers began to gain popularity in the industry, we began to hear stories of people losing hands, but again, not so many reports of fatalities. One thing we noticed at each successive TCI EXPO, the in-feed hoppers got higher and deeper than the preceding models. We are convinced now that just because we didn’t hear about an accident as gruesome as going through a chipper didn’t mean it wasn’t happening somewhere to someone.

Compared to a disc chipper, you’re going to have to work harder at getting processed by a drum chipper, but both may instantly be converted for use as a meat grinder, if you are so inclined.

One popular method would be to stand at the center of the feed table, lean over at the waist and reach as close to the blades as you can to shove those little sticks in; because a push stick is too much bother. Failing that, you could also back the chipper up to a landscape berm or a retaining wall so that the feed table is even with or below the level of brush to be chipped. From this lofty vantage point, you could easily stand on the feed table, shoving in brush until you slipped and fell into the blades.

With this background in place, we may now return to the primary subject of this monograph. The Journal article frequently cited in newspaper accounts of chipper accidents has a most distinguished lineage: “Fatal and Nonfatal Occupational Injuries Involving Wood Chippers – United States, 1992-2002” (Journal of the American Medical Association, vol. 293: 416-418) was based upon a Center for Disease Control (CDC) analysis of the same title. The report compiled 11 years of data from the Bureau of Labor Statistics (BLS) census of fatal and nonfatal occupational injuries involving chippers.

The article concluded that a total of 31 occupational injury deaths were associated with operating a wood chipper during the reporting period. The workers were all males and many were between 25 and 34 years of age at the time of the death. The main cause of the fatalities was being caught in the machine, followed by being struck by flying objects. The report also estimated 2,042 nonfatal injuries from chipper accidents during the same period. The only thing wrong with the report is the fact that, while 31 deaths and 2,042 injuries during the reporting period are certainly cause for concern, the actual number of fatalities is truly shocking!

An ongoing research project on tree worker safety being conducted by South Dakota State University (SDSU) indicates that chipper fatalities are occurring sometimes as often as twice a month, as opposed to the oft-cited statistic of less than three a year. To contrast the South Dakota State University data with the AMA/CDC/BLS statistics: five tree workers were killed in separate accidents involving chippers during a nine week period at the end of 2008. One was killed reaching in to clear a jam. In another, the worker was pulled in while grabbing a branch that was stuck in the running machine. The third and fourth workers were pulled in feet-first while clearing jams. The fifth was clearing branches from a chipper that had been propped up on blocks, crushing him to death when it fell.

These accidents underscore two major concerns. First, the BLS under-reporting creates an unrealistically rosy view of the workplace and a false sense of security. If tree workers believe that less than three people a year are killed while chipping, they may think the odds of having an accident are very low. On the other hand, if tree workers knew that at least one person was KWC (killed while chipping) every two weeks or so, they might be more inclined to quit standing on the feed table and begin working in a safer manner.
Second, since chipper accidents are this common, what must be done to reduce them?
The SDSU compilation of chipper accidents from 1997 to 2008 indicates that the majority of the fatalities involve workers engaged in activities that willfully violate accepted industry safety standards as well as manufacturer recommendations. In fact they were all doing exactly what all chipper manufacturers say not to do! In one instance, as a worker was using his foot to push branches into the in-feed rollers, his shoe became caught on a stub, pulling him into the machine up to his waist. He died within minutes.

There are numerous accidents that have a similar set up and outcome; a worker stands with a foot on the feed table to clear out a jam or kick brush. His or her shoe or pant leg becomes entangled in the brush, pulling them into the machine.

Chipper accidents are not always fatal, but they are rarely minor. Nonfatal injuries with chippers tend to be very serious, often requiring amputation of a foot or leg up to the knee. Everyone operating a chipper should know that using a foot to feed brush, clear a jam or kick in a log are not safe work practices. Unfortunately this risky behavior persists because too many workers have gotten away with it time and time again without any mishaps. Russian roulette is Russian roulette no matter how the game is played.

A newspaper report of a “foot-first” chipper accident included this quote from another tree care company manager who said such accidents were the fault of the machine: “If someone in this business says they haven’t used their foot to free a log, they’d be lying.” He is probably close to the truth, but we are deceiving ourselves if we blame the tool for the tragic results of our own behavior. No machine’s safety features should be blindly depended upon to save you from yourself. For example: don’t count upon the reverse bar to save you if your foot gets caught. As you are being fed into the machine, you are not likely to hit the reverse bar in time: you’ll find you cannot reach it or the situation unfolds faster than you can react. In one accident as the worker was being pulled in feet-first, a co-worker hit the reverse bar without any effect. The reverse bar was inoperable, and instead of shutting down the machine, several panicked workers continued to keep hitting the bar as their screaming co-worker was pulled completely through the machine.

The second most common accident is being pulled into the machine hands-first. A common scenario finds the crew wondering where the chipper operator disappeared to, only to discover legs sticking out of the in-feed hopper. During the task of feeding in short branches, the worker’s glove is grabbed, pinched or snagged, pulling the hand through the rollers and into the machine, with the rest of the worker’s body following close behind. The chipper may stop at the shoulder, but that is scant comfort for the victim. If the machine is reversed quickly enough, the “lucky” victims only suffer an arm amputated to the elbow, above the wrist, or perhaps only a finger or two is lost. One “lucky” victim who got pulled in by a glove, held onto the reversing bar for dear life. It didn’t reverse, but his grip on the bar kept him from going through. With his head caught in the rollers and his neck broken, the accident was classified as nonfatal, but the victim in this case is paralyzed for life from the neck down.

The third common accident involves being struck by the shroud (aka hood or cover) covering the disc itself. The usual scenario here involves a worker opening the hood to clear a jam before the chipper disc has completely stopped. The disc can hit the shroud, tearing it loose from the hinges, striking the worker. In the aftermath of one of these accidents, a fellow worker said “He knew he wasn’t supposed to remove the cover while the disc was spinning.”

Although being fed into the chipper or struck by flying objects factor into the vast majority of chipper accidents, they are not the only causes. In the last few months, there have also been two vehicular accidents involving chippers. In both cases, the chipper came free of the hitch, striking another vehicle or guardrail. There was also one suicide involving a chipper in 2008.

Manufacturers continually strive to improve their equipment to make it as productive, safe and foolproof as possible. The problem is, someone else is continually turning out “new and improved fools,” and once again, instead of blaming the equipment, we also need to start taking our own work behavior into account as a root cause. Chippers are one of the many tools that make our work possible. We simply cannot ban chippers to solve the problem. When used as the manufacturer intends and our standards require, they are safe. However, each year tree workers die because someone ignored or failed to enforce, safe work practices. Next time you think, “I’ll just kick that log in,” consider the fact that you might find yourself arriving at the site of a grisly fatality about 10 minutes ahead of the EMT.

Our review and analysis of the AMA’s interpretation of the CDC report make clear a number of extremely important considerations. A far more realistic number of chipper fatalities for 1992-2002 would be triple digit not double digit! Regardless of the type of high-risk occupation, as accidents are arranged in order of severity, a pyramid-shaped structure appears. Visualize riding in an elevator through the center of a pyramid as the elevator operator calls off the floors. You enter the elevator on the first floor – Close Calls and Near Misses; second floor – Minor Injuries; third floor – Serious Accidents; fourth floor – Fatalities, all remaining passengers must exit!

With a 10-fold increase in presumed chipper fatalities, all statistics below the fourth floor would also increase dramatically as all levels of the pyramid would have to be adjusted upward – way upward.

Looking back, we are convinced that incidents were far more common “in the old days” than believed or publicized. Not that many years ago, the community of arborists was far more local and regional than we were national and international. Companies have always been reluctant to go public with their accidents, but more seem willing now than ever before. Now that we are linked up globally through the Internet, with Google, Web sites, arborist forums and all the other wonders of the Information Age, news that once took a long time to get around, if ever, is just another e-mail or text message.

SDSU’s tree worker safety research has taken us beneath the tip of the iceberg in an effort to understand the nature and severity of accidents in our profession, but we’ve still got a long way to go. As we learn more about how we are killing ourselves, we are learning where the mindsets have to change. This call to action is not new; it’s just getting louder as it is being embraced by more and more concerned people. The book, Arborist Equipment (Blair, 1994) devoted an entire chapter to the “Mindset of Safety” as an early effort to identify, but not quantify, the nature and causes of accidents in tree care.

Chippers are as important to production as chain saws. Both are inherently dangerous, but both may be operated safely and efficiently for a worker’s entire career without harm. All one has to do is to exercise common sense and a have full understanding of how to properly use and maintain the equipment, whatever it is. It seems so easy and yet for some people it must be really, really hard to understand. Don’t be one of “them.” This is one time that you do not want to be “in the chips!”

Seventy-five years ago, in a by-gone era when brush was often burned and never chipped, when all cuts no matter how large were made with hand saws, Millard F. Blair first posted a sign in his shop that said simply: STOP! THINK FIRST! It was good advice then and it is still good advice today: STOP! THINK FIRST!

Dr. John Ball is a professor of forestry at South Dakota State University where he instructs courses in tree care as well as conducts research in a number of fields, including tree worker safety. He can be reached at john.ball@sdstate.edu.

Donald F. Blair is the founder of the Sierra Moreno Mercantile Company, Inc. and the director of the M. F. Blair Institute of Arboriculture. Blair is also vice-chair of the ANSI Z133 Accredited Standards Committee.