Safety Issues


Truck Driver Suffocates when Engulfed while Clearing Jammed Woodchips being Unloaded from an Open Top Trailer with a Movable Floor Unloading System

The 47-year-old experienced male truck driver had been employed by a wholesale mulch company for 10 years.  The company had locations in multiple states, resulting in interstate driving.  The day before the incident, he worked 10 hours and slept overnight at a rest area in the sleeper bunk of his truck's cab.  



On a clear chilly Thursday morning, the truck driver arrived at a location to pick up a load of woodchips.  Once woodchips were loaded to the top of the trailer, he drove to the company location to unload the woodchips.  The trailer had an open top, one central cross stability bar, a rear gate, and two fixed ladders, one attached to the exterior of the trailer and the other was located inside the trailer.  A movable floor unloading system had been installed in the trailer and was made up of 26 narrow aluminum floor slats running the length of the trailer and three cylinders.  Every third floor slat was attached to a cross piece that was attached to a hydraulic cylinder allowing these floor slats to move together.  One of the three cylinders would engage at a time moving the attached floor slats towards the front of the trailer.  Once all floor slats were at the most forward point, then all three cylinders would engage at once in the reverse direction moving all of the floor slats simultaneously towards the rear of the trailer.  This would continue until the trailer was unloaded.  The truck driver was found by co-workers in the offloaded woodchip pile behind the truck.




When the truck driver arrived at the company location he opened the trailer’s rear gate and activated the movable floor unloading system to start the unloading process.  It was reported that woodchips would routinely jam at the cross stability bar during unloading and that drivers would enter the trailers to clear the jams and to start manually sweeping the trailer floors.  Eyewitnesses observed the truck driver climb the exterior fixed ladder to the top edge of the trailer.  It appears that the truck driver stepped from the top edge of the trailer onto the woodchip pile possibly to clear a jam and that a void within the woodchips caused the pile to give way.  He fell into the pile and was engulfed and suffocated by the woodchips.  The movable floor unloading system continued to offload woodchips and eventually the truck driver was offloaded as well and found by co-workers. 

Occupational injuries and fatalities are often the result of one or more contributing factors or key events that are part of a larger sequence of events that ultimately result in the injury or fatality.  The following items were identified as key contributing factors in this incident that ultimately led to the fatality: 1) overloading the trailer with woodchips; and 2) entering a trailer loaded with woodchips, which is a confined space, during unloading to clear a jam and/or start sweeping the trailer floor.



  • Minimize product jamming by ensuring that trailers equipped with both cross stability bars and movable floor unloading systems are not loaded up to or above the cross stability bar.

  • Ensure trailers with movable floor unloading systems are either equipped with automatic sweeping tarps or that manual sweeping does not begin until after the entire trailer has been offloaded.

  • Identify all confined spaces, such as trailers loaded with woodchips, and develop, implement, and enforce a permit-required confined space program.

Massachusetts Department of Public Health
Occupational Health Surveillance Program
250 Washington Street, 4th Floor
Boston, MA 02108

Safety Issues is presented by the National Institute for Occupational Safety and Health (NIOSH) in partnership with the National Truckers Association (NTA), with major contributions from State partners funded by NIOSH through the Fatality Assessment and Control Evaluation (FACE) Program.  The goal of the FACE Program is to prevent occupational fatalities across the nation by identifying and investigating work situations at high risk for injury and then developing and disseminating prevention strategies to those who can intervene in the workplace. State partners who contribute Safety Issues postings based on recent investigative reports are California, Kentucky, Massachusetts, Michigan, New York, Oregon, and Washington.

This month’s Safety Issues is based on an investigative report from the Massachusetts FACE Program. The complete detailed Massachusetts FACE Investigation Report: #08MA001 includes additional case information, recommendations and discussion. This report can be found at Additional MA FACE Investigation Reports, Annual Reports, Hazard Alerts and other publications can be accessed through the Massachusetts Department of Public Health at

The Safety Issues and Investigation Reports which are the products of NIOSH Cooperative State partners are presented here in their original unedited form from the states. They are intended for educational purposes only. The findings and conclusions in each report are those of the individual Cooperative State partner and do not necessarily reflect the views or policy of the NIOSH.

The highlighted text is dependent on which State FACE submitted the safety issue, so it will change each month.