Mowers that have been modifi ed for use in greenhouses may
be hazardous. In some N.C. greenhouses, typical walk-behind
gas-powered lawn mowers, like the ones you might use to cut a
lawn, have been removed from their original wheelbase and then
fi tted onto a metal carriage.
The carriage and the mower are then attached to a boom. The
boom—a long, metal arm that extends the width of a plant bed,
35 feet—is mounted on a rail system and allows a worker to walk
down a path in the greenhouse pushing the boom-mounted mowers.
The mower is then used to trim the tobacco or sweet potato plants
growing in the plant beds.
The mowers, as manufactured, are equipped with a safety device
known as the operator presence control (OPC) located on the handle of
the mower. The OPC allows the engine to run when it is squeezed
against the mower handle. When you use a mower as it was manu-factured
and release the OPC safety device on the handle, the mower
shuts off.
Injury in 2014: A farmworker was mowing sweet potato plants in a
greenhouse using a modifi ed lawn mower. The mower was modifi ed in
that the handle with the OPC safety device had been removed. The handle
and safety device had been replaced with a simple toggle switch used to
stop and start the machine. At noon on the day of the accident, when it was
time to break for lunch, the worker realized that the toggle switch on his
machine was broken in the “on” position. The worker asked for help from
another employee, who turned the machine off by disconnecting the wires
to the toggle switch and touching the wires to the metal on the frame. The
mower manual says that the spark plug wire needs to be secured away
from the spark plug to prevent accidental starting prior to repair or cleaning.
When the worker returned from lunch the mower was still off. The worker
began to clean the mower and the blades. The mower started up as he
cleaned the blades, amputating three of the employee’s fi ngers. Since the
injury, the employer has developed a safer mechanism for mowing its plant
beds and implemented new work rules regarding use of the mowers.
Summary
Lawn mowers with modifi cations that alter or disable the OPC
system or that are not in accordance with manufacturer instructions
may be hazardous. Modifi ed mowers may reduce employee safety.
For Growers: Improving the Safety of Your Mowers:
Never disable safety mechanisms on machinery.
Make sure all guards and safety devices are in place prior
to operation.
	
	

hazard
Division of Occupational Safety and Health
1101 Mail Service Center, Raleigh, NC 27699-1101
Cherie Berry, Commissioner of Labor
1-800-625-2267  wwww.nclabor.com
Unsafe Modifi cation of Mowers for Greenhouse Use
Modifi ed mower mounted on boom.
NCDOL Photo Library
NCDOL Photo Library
Toggle switch used to activate modifi ed mower. continued on page 2
NCDOL Photo Library
NCDOL Photo Library
New mechanism to activate mower, replacing toggle switch.
HA1475