In jury As so ci ated with Working Near

or Op er ating Wood Chip pers

 De scrip tion of HAZARD

Ac cord ing to the Bu reau of La bor Sta tis tics (BLS) Cen sus of Fa tal Oc cu pa tional In juries (CFOI),

11 workers lost their lives dur ing 1992 through 1997 while work ing near mo bile wood chip pers. In seven of 

the incidents, the vic tim was caught by the feed mech a nism and pulled through the chip per knives. The vic -

tims in four of the in ci dents were struck by hoods (guards that cover the ro tat ing chip per knives) that sep arated from the ma chines af ter be ing im prop erly opened or closed while knives were still ro tat ing.

Dur ing 1998, the Na tional In sti tute for Oc cu pa tional Safety and Health (NIOSH) re ceived two ad di tional

re ports of worker deaths from op er at ing wood chip pers. These in ci dents il lus trate the two most com mon

causes of fa tal in jury: be ing fed through the chip per knives or be ing struck by the chip per disc hood. The

incidents were in ves ti gated as part of the NIOSH Fa tal ity As sess ment and Con trol Eval u a tion (FACE)

pro gram.

Self-feeding mo bile wood chip pers com monly used dur ing tree trim ming op er a tions con sist of a feed

mech a nism, knives mounted on a ro tat ing chip per disc or drum, and a power plant. Tree branches and trunk 

sec tions fed man u ally into the ma chine’s infeed hop per are grabbed by the feed mech a nism or chip per

knives. The chip per disc or drum ro tat ing be tween 1,000 and 2,000 rpm cuts and pro pels wood chips

through the dis charge spout usu ally into a chip truck. The hous ing con tain ing the chip per disc or drum is

sec tioned and in cludes a re mov able hood that al lows ac cess to ma chine com po nents for main te nance.

Caught-By Haz ard: Workers feed ing ma te rial into self-feeding wood chip pers are at risk of be ing fed

through the chip per knives if they reach or fall into the infeed hop per or be come

en tan gled in branches feed ing into the ma chine.

Case Study: A 28-year-old grounds man died af ter he

was caught and pulled into a wood chip per. The vic tim

and two co work ers, a fore man and a climber, were

clean ing up limbs af ter prun ing a tu lip pop lar be hind a

town house. The co work ers were be hind the build ing

gath er ing loose branches while the vic tim was in front

op er at ing the chip per. The co work ers be gan drag ging

brush to the chip per. As the climber ap proached the

chip per, he saw the vic tim’s legs stick ing out of the

infeed hop per. In ves ti ga tors con cluded that the vic tim

ei ther fell or reached into the infeed hop per while feed -

ing short branches. His hands were caught by the feed

mech a nism, forc ing his head and up per torso into the

chip per knives.

HID 8

HAZARD ID
Struck-By Haz ard: Workers are at risk of be ing struck by un latched, im prop erly se cured, or dam aged

or im prop erly main tained hoods that may be thrown from the wood chip per af ter

con tact ing the ro tat ing chip per knives.

Case Study: A 46-year-old la borer at a mu nic i pal

waste-management fa cil ity died af ter he was struck by

the fly ing chip per disc hood from an op er at ing brush

chip per. He had been feed ing ma te rial into a chip per

that had been con verted to a sta tion ary ma chine. He

had shut off the chip per to re move jammed ma te rial,

but opened the hood be fore the chip per disc had

stopped com pletely. The ro tat ing disc hit the hood as

he opened it and tore it loose from its hinges. The hood

struck the vic tim in the head and chest. He died the

next day with out re gain ing con scious ness. In ves ti gation showed that the hood hinges had been dam aged,

al low ing ex ces sive side move ment as the hood was

swung open.

 Rec om men da tions for Pre ven tion

To pro tect work ers from be ing caught by the chip -

per feed mech a nism, em ploy ers should en sure the

fol low ing:

• All safety de vices and con trols, such as emer -

gency shut-off de vices, are tested and ver i fied

to be func tion ing prop erly be fore the chip per is

used.

• Workers are trained in safe work pro ce dures,

in clud ing op er at ing wood chip per safety devices

and safety con trols. These pro ce dures should be

based on the man u fac turer’s rec om men da tions

for each ma chine.

• At least two work ers are in close con tact with

each other when op er at ing the chip per.

• Workers wear close-fitting cloth ing, gloves

with out cuffs, trou sers with out cuffs and

skid-resistant foot wear. Cloth ing should be

kept tucked in.

• Worker’s hands and feet re main out side the

infeed hop per.

• Workers feed brush and limbs into the infeed

hop per butt end first.

• Workers feed ing ma te rial are po si tioned at the

side of the ma chine to al low quick op er a tion of

the emer gency shut-off de vice and min i mize

risk of en tan gle ment in branches. Be cause of

dif fer ences among ma chines, the man u facturer’s op er at ing man ual should be con sulted

for guid ance. Safe feed ing of some disc-type

chip pers re quires the worker to be on the right

side.

• Workers walk away once the feed mech a nism

has grabbed the ma te rial.

• Workers lay short ma te rial on top of lon ger ma -

te rial that is feed ing or use a lon ger branch to

push it through the infeed hop per.

• Workers load small raked-up ma te rial such as

twigs and leaves di rectly into the chip truck or

in trash cans or bags in stead of feed ing it into 

the chip per.
• Workers keep the area around the wood chip per 

free of trip ping haz ards.

• Workers wear hard hats, eye pro tec tion, and

hear ing pro tec tion.

To pro tect work ers against be ing struck by fly ing

hoods cov er ing chip per discs or drums, em ploy ers

should en sure the fol low ing:

• Wood chip pers are in spected each work ing day

be fore startup for de fects such as bro ken or

miss ing hood latches and pins or cracked and

worn hinges. Bro ken, dam aged, or miss ing ma -

chine com po nents should be re paired or re -

placed be fore the ma chine is placed in ser vice.

• The hood cov er ing the chip per knives is com -

pletely closed and latched ac cord ing to man ufac turer’s rec om men da tions be fore start ing the

ma chine.

• Be fore pro cess ing ma te rial and un less the man -

u fac turer rec om mends oth er wise, the ma chine

is run at the low est pos si ble speed while work -

ers lis ten for noise that might in di cate bro ken or 

loose ma chine parts. If un usual noise is de -

tected, the ma chine should be shut down im me -

di ately and eval u ated by a com pe tent per son. If

nec es sary, the ma chine should be re paired be -

fore be ing placed in ser vice.

• All in ter nal ma chine parts have come to a com -

plete stop be fore the hood cov er ing the chip per

disc or drum is opened.

 For More In for ma tion

NIOSH en cour ages em ploy ers and work ers to

con sult ANSI Z133.1–1994, Amer i can Na tional

Standard for Tree Care Op er a tions—Pruning,

Trimming, Re pairing, Main taining, and Re moving

Trees, and Cut ting Brush—Safety Re quire ments,

for ad di tional in for ma tion.

To ob tain more in for ma tion about this haz ard or

other work place haz ards

The FACE Pro gram is con ducted by NIOSH. The

ob jec tive of the pro gram is to iden tify work sit u ations at high risk for fa tal in jury and for mu late and

dis sem i nate pre ven tion strat e gies to those who can

in ter vene in the work place.

 Ac knowl edg ments

The prin ci pal con tri bu tors to this pub li ca tion are:

Paul H. Moore and Vir gil J. Casini, NIOSH

Division of Safety Re search, Su san Shep herd,

Mas sa chu setts De part ment of Health, and Charles

Carson, Texas Worker’s Com pen sa tion Com mission. Jerome P. Flesch pro vided tech ni cal re view,

and Vanessa Becks, Su san Kaelin, and Kristina

Wasmund pro vided desk top pub lish ing.

August 1999 DHHS (NIOSH) Publication No. 99–145

—call NIOSH at 1–800–35–NIOSH

(1–800–356–4674), or

—visit the NIOSH Web site at

http://www.cdc.gov/niosh.html

U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES

Public Health Service

Centers for Disease Control and Prevention

National Institute for Occupational Safety and Health