Make sure that the machine has come to a complete stop before removing access panels. When performing maintenance on the machine, shut off the engine, remove the key (if electric start) or temporarily disable the machine. Always feed material butt-end first. Feed shorter material into the machine by laying it on top of longer material. Do not feed material that you've raked up or scraped off the ground. You should simply place this material on top of the material that you've already chipped, as it may contain dirt and rocks that may damage the chipper. Chippers with dull knives and anvils do not feed well. This becomes a problem with any machine but especially on manual-feed units. If your operator then tries to force the material into the feed shoot, he or she creates a greater danger of slipping and getting too close to the chipper knives. Do not operate the chipper alone. Always be prepared for a fire or injury by having a fire extinguisher attached to the machine and a first-aid kit handy. It is the operator's responsibility to make sure that flying chips and debris will not harm bystanders.