DIS CLAIMER

Men tion of any com pany or prod uct does not con sti tute en dorse ment by the

Na tional In sti tute for Oc cu pa tional Safety and Health.

Copies of this and other NIOSH doc u ments are avail able from

Na tional In sti tute for Oc cu pa tional Safety and Health

Pub li ca tions Dis sem i na tion

4676 Co lum bia Park way

Cincinnati, OH 45226–1998

Fax num ber: (513) 533–8573

Tele phone num ber: 1–800–35–NIOSH (1–800–356–4674)

E-mail: pubstaft@cdc.gov

To re ceive other in for ma tion about oc cu pa tional safety and health prob lems,

call 1–800–35–NIOSH (1–800–356–4674), or visit the NIOSH Web site at

www.cdc.gov/niosh

DHHS (NIOSH) Pub li ca tion No. 99–110

July 1999

This docu ment is in the pub lic do main and may be freely cop ied or re printed.
Preventing Worker Deaths from Uncontrolled Release of

Electrical, Mechanical, and Other Types of Hazardous Energy

Take the fol low ing steps to pro tect your self if you

in stall or ser vice equip ment and sys tems:

•Fol low OSHA reg u la tions.

•Iden tify and la bel all sources of haz ard ous

en ergy.

•Be fore be gin ning work, do the fol low ing:

1. De-energize all sources of hazardous

energy:

— Dis con nect or shut down en gines or

mo tors.

— De-energize elec tri cal cir cuits.

— Block fluid (gas or liq uid) flow in

hy drau lic or pneu matic sys tems.

— Block ma chine parts against mo tion.

2. Block or dissipate stored energy:

— Dis charge ca pac i tors.

— Re lease or block springs that are

un der com pres sion or ten sion.

— Vent flu ids from pres sure ves sels,

tanks, or ac cu mu la tors— but never

vent toxic, flam ma ble, or ex plo sive

sub stances di rectly into the atmosphere.

3. Lockout and tagout all forms of

hazardous energy— including electrical

breaker panels, control valves, etc.

4. Make sure that only one key exists for

each of your assigned locks and that

only you hold that key.

5. Verify by test and/or observation that

all energy sources are de-energized.

6. Inspect repair work before removing

your lock and activating the equipment.

7. Make sure that only you remove your

assigned lock.

8. Make sure that you and your coworkers are clear of danger points

before re-energizing the system.

•Par tic i pate in all train ing pro grams of fered by

your em ploy ers.

Please tear out and post. Dis trib ute cop ies to work ers. See back of sheet to or der com plete Alert.

WARNING!

Workers who install or service equipment and systems may be

injured or killed by the uncontrolled release of hazardous energy.

Re printed with per mis sion of IDESCO Cor po ra tion, © 1999.

Only the worker who in stalls a lock and tag should

re move them af ter work is com plete and in spected.
For ad di tional in for ma tion, see NIOSH Alert: Pre venting Worker

In juries and Deaths from Haz ard ous En ergy Re lease [DHHS

(NIOSH) Pub li ca tion No. 99–110. Sin gle cop ies of the Alert are available free from the fol low ing:

Na tional In sti tute for Oc cu pa tional Safety and Health

Pub li ca tions Dis sem i na tion

4676 Co lum bia Park way

Cincinnati, OH 45226–1998

Fax num ber: (513) 533–8573

Phone num ber: 1–800–35–NIOSH (1–800–356–4674)

E-mail: pubstaft@cdc.gov

U.S. De part ment of Health and Hu man Ser vices

Pub lic Health Ser vice

Cen ters for Dis ease Con trol and Pre ven tion

Na tional In sti tute for Oc cu pa tional Safety and Health
Pre venting Worker Deaths from Un con trolled Re lease of

Elec tri cal, Me chan i cal, and Other Types of Haz ard ous En ergy

The Na tional In sti tute for Oc cu pa tional

Safety and Health (NIOSH) re quests

assistance in pre vent ing the death or

in jury of work ers ex posed to the un expected or un con trolled re lease of hazard ous en ergy. In this Alert, haz ard ous

en ergy is any type of en ergy in suf ficient quan tity to cause in jury to a

worker. Com mon sources of haz ard ous

en ergy in clude elec tric ity, me chan i cal

mo tion, pres sur ized air, and hot and

cold tem per a tures. Haz ard ous en ergy

re leases may oc cur dur ing the in stal lation, main te nance, ser vice, or re pair of

ma chines, equip ment, pro cesses, or

sys tems. In ves ti ga tions con ducted as

part of the NIOSH Fa tal ity As sess ment

and Con trol Eval u a tion (FACE) Program sug gest that de vel op ing and

follow ing haz ard ous en ergy con trol

pro ce dures could pre vent worker

injuries and fa tal i ties.

This Alert de scribes five fa tal in ci dents

in which work ers con tacted un controlled haz ard ous en ergy dur ing in stalla tion, main te nance, ser vice, or re pair

work. To pre vent such deaths, the rec -

om men da tions in this Alert should be

fol lowed by ev ery em ployer, man ager,

su per vi sor, and worker who in stalls,

main tains, ser vices, or re pairs machines, equip ment, pro cesses, or systems. NIOSH re quests that trade jour nal

ed i tors, safety and health of fi cials, and

oth ers re spon si ble for worker safety

and health bring this Alert to the at tention of em ploy ers and work ers who are

at risk.

1

WARNING!

Workers who install or service equipment and systems may be

injured or killed by the uncontrolled release of hazardous energy.

Re printed with per mis sion of IDESCO Cor po ra tion, © 1999.

Only the worker who in stalls a lock and tag should

re move them af ter work is com plete and in spected.
BACK GROUND

Num ber of Workers Killed

No de tailed na tional data are avail able on

the num ber of work ers killed each year by

con tact with un con trolled haz ard ous en ergy.

How ever, dur ing the pe riod 1982–1997,

NIOSH in ves ti gated 1,281 fa tal in ci dents as

part of their FACE Pro gram. Of these, 152

involved in stal la tion, main te nance, ser vice,

or re pair tasks on or near ma chines, equip -

ment, pro cesses, or sys tems. Be cause the

FACE pro gram was ac tive in only 20 States

be tween 1982 and 1997, these fa tal i ties

repre sent only a por tion of the U.S. work ers

who were killed by con tact with un controlled haz ard ous en ergy.

Con trib uting Fac tors

Re view of these 152 in ci dents sug gests

that three re lated fac tors con trib uted to

these fa tal i ties:

• Fail ure to com pletely de-energize, iso -

late, block, and/or dis si pate the en ergy

source (82% of the in ci dents, or 124 of

152)

• Fail ure to lock out and tagout en ergy

con trol de vices and iso la tion points af -

ter de-energization (11% of the in cidents, or 17 of 152)

• Fail ure to ver ify that the en ergy source

was de-energized be fore be gin ning

work (7% of the in ci dents, or 11 of 152)

In a study con ducted by the United Auto

Workers (UAW), 20% of the fa tal i ties (83 of

414) that oc curred among their members

be tween 1973 and 1995 were attributed to

in ad e quate haz ard ous en ergy con trol pro -

ce dures— spe cif i cally, lock out/tagout proce dures. The en ergy sources in volved in

these fa tal i ties in cluded ki netic, po ten tial,

elec tri cal, and ther mal en ergy [UAW

1997].

CUR RENT OSHA

REG U LA TIONS

Cur rent Oc cu pa tional Safety and Health

Ad min is tra tion (OSHA) stan dards for

general in dus try are es tab lished to prevent inju ries and fa tal i ties from con tact with

haz ard ous en ergy [29 CFR* 1910.147].

This stan dard re quires em ploy ers to “es -

tab lish a pro gram con sist ing of en ergy con -

trol pro ce dures, em ployee train ing and

pe ri odic in spec tions to en sure that be fore

any em ployee per forms any ser vic ing or

main te nance on a ma chine or equip ment

where the un ex pected en er giz ing, start up

or re lease of stored en ergy could oc cur

and cause in jury, the ma chine or equipment shall be iso lated from the en ergy

source, and ren dered in op er a tive.”

Other OSHA stan dards for gen eral in dus try

cite the need for de-energizing elec tri cal

en ergy and lock ing and tag ging elec tri cal

cir cuits and equip ment be fore per form ing

main te nance and ser vic ing tasks. The fol -

low ing OSHA stan dards con tain lockout/tagout-related re quire ments:

1910.146 Per mit-Required Con fined

Spaces

1910.177 Ser vicing Multi-Piece and

Sin gle Piece Rim Wheels

1910.178 Powered In dus trial Trucks

1910.179 Over head and Gan try

Cranes

*Code of Fed eral Reg u la tions. See CFR in

ref er ences.

2 Haz ard ous En ergy
1910.181 Der ricks

1910.213 Woodworking Ma chin ery

1910.217 Me chan i cal Power

Presses

1910.218 Forging Ma chines

1910.261 Pulp, Pa per, and

Pa per board Mills

1910.262 Textiles

1910.263 Bak ery Equip ment

1910.265 Saw mills

1910.269 Elec tric Power

Gen er a tion, Trans mis sion,

and Dis tri bu tion

1910.272 Grain Han dling

1910.305 Wiring Methods,

Com po nents, and

Equip ment for Gen eral Use

1910.306 Spe cific Pur pose

Equip ment and

In stal la tions

1910.333 Se lec tion and Use of Work

Prac tices

OSHA stan dards for con struc tion also con -

tain re quire ments for pro tect ing work ers

from elec tri cal haz ards [29 CFR 1926.416

and 29 CFR 1926.417]. These stan dards

re quire that work ers ex posed to any part of

an elec tri cal power cir cuit be pro tected

through de-energizing and ground ing of

the cir cuit or through ap pro pri ate guard ing.

These stan dards also re quire that all

de-energized cir cuits be ren dered in op er able and tagged out.

FORMS OF HAZ ARD OUS

EN ERGY

Workers may be ex posed to haz ard ous

energy in sev eral forms and com bi na tions

dur ing in stal la tion, main te nance, ser vice,

or re pair work. A com pre hen sive haz ardous en ergy con trol pro gram should address all forms of haz ard ous en ergy

[NIOSH 1983]:

•Ki netic (me chan i cal) en ergy in the

mov ing parts of me chan i cal sys tems

•Po ten tial en ergy stored in pres sure

ves sels, gas tanks, hy drau lic or pneu -

matic sys tems, and springs (po ten tial

en ergy can be re leased as haz ard ous

ki netic en ergy)

•Elec tri cal en ergy from gen er ated elec -

tri cal power, static sources, or elec trical stor age de vices (such as bat ter ies

or ca pac i tors)

•Ther mal en ergy (high or low tem per a ture)

re sult ing from me chan i cal work, ra di ation, chem i cal re ac tion, or elec tri cal

re sis tance

CASE RE PORTS

As part of the FACE Pro gram from 1982

through 1997, NIOSH in ves ti gated 152

fatal in ci dents in which work ers con tacted

un con trolled haz ard ous en ergy. The fol lowing case re ports sum ma rize five of these

in ves ti ga tions.

Case No. 1— Uncontrolled Ki netic

En ergy

A 25-year-old male worker at a con crete

pipe man u fac tur ing fa cil ity died from in ju ries

Haz ard ous En ergy 3
he re ceived while clean ing a rib bon-type

con crete mixer. The vic tim’s daily tasks

included clean ing out the con crete mixer at

the end of the shift. The clean-out pro ce dure

was to shut off the power at the breaker

panel (ap prox i mately 35 feet from the mixer),

push the tog gle switch by the mixer to

make sure that the power was off, and then

en ter the mixer to clean it.

No one wit nessed the event, but in ves ti gators con cluded that the mixer op er a tor had

shut off the main breaker and then made

a tele phone call in stead of fol low ing the

nor mal pro ce dure for check ing the mixer

be fore any one en tered it. The vic tim did not

know that the op er a tor had de-energized

the mixer at the breaker. Thinking he was

turn ing the mixer off, he ac ti vated the

breaker switch and en er gized the mixer.

The vic tim then en tered the mixer and be -

gan clean ing with out first push ing the tog -

gle switch to make sure that the equip ment

was de-energized. The mixer op er a tor re -

turned from mak ing his tele phone call and

pushed the tog gle switch to check that

the mixer was de-energized. The mixer

started, and the op er a tor heard the vic tim

scream. He went im me di ately to the main

breaker panel and shut off the mixer.

Within 30 min utes, the emer gency med i cal

ser vice (EMS) trans ported the vic tim to a

lo cal hos pi tal and then to a lo cal trauma

cen ter. He died ap prox i mately 4 hours later

[NIOSH 1995].

Case No. 2— Un con trolled

Elec tri cal En ergy

A 53-year-old jour ney man wireman was

elec tro cuted when he con tacted two

energized, 6.9 -kilo volt buss ter mi nals. The

vic tim and two co work ers (all con tract

employees) were in stall ing elec tri cal

com po nents of a sul fur di ox ide emis sion

con trol sys tem in a 14-compartment switch

house.

The cir cuit breaker pro tect ing the in ter nal

buss† within the switch house had been

trip ped out and marked with a tag— but it

had not been se cured by lock ing. This pro -

ce dure was con sis tent with the haz ard ous

en ergy con trol pro ce dures of the power

plant.

The vic tim and his co work ers were wip ing

down the in di vid ual com part ments be fore a

prestartup in spec tion by power plant per -

son nel. With out the knowl edge of the vic -

tim and his co work ers, power plant

per son nel had en er gized the in ter nal buss

in the switch house. When the vic tim be gan

to wipe down one of the com part ments at

the south end of the switch house, he con -

tacted the A-phase buss ter mi nal with his

right hand and the C-phase buss ter mi nal

with his left hand. This act com pleted a

path be tween phases, and the vic tim was

elec tro cuted.

A coworker walk ing past the vic tim dur ing

the in ci dent was blown back ward by the

arc ing and re ceived first-degree flash

burns on his face and neck. A sec ond

coworker at the north end of the switch

house heard the ex plo sion and came to

help. He no ti fied the con trac tor’s safety co -

or di na tor by ra dio and re quested EMS.

The EMS re sponded in about 15 min utes

and trans ported the vic tim to a lo cal hos pital emer gency room where he was pronounced dead [NIOSH 1994].

†A con duct ing bar, rod, or tube that car ries heavy

cur rents to sup ply sev eral elec tric cir cuits.

4 Haz ard ous En ergy
Case No. 3— Un con trolled Ki netic

En ergy

A 38-year-old worker at a county san i tary

land fill died af ter fall ing into a large trash

com pac tor used to bale card board for

recycling. The card board was lifted 20 feet

by a belt con veyor and fed through a 20-

by 44-inch open ing into a hop per. The

hopper had au to matic con trols that ac tivated the baler when enough ma te rial col -

lected in the bal ing cham ber. When the

baler was ac ti vated, ma te rial in the cham -

ber was com pressed by a ram that en tered

the cham ber from the side. Ex cess ma terial above the cham ber was trimmed by a

shearer.

On the day of the in ci dent, card board

jammed at the con veyor dis charge open -

ing. With out stop ping, de-energizing, or

lock ing out the equip ment, the vic tim rode

the con veyor up to the dis charge open ing

to clear the jam. He fell into the hop per and

the bal ing cy cle was au to mat i cally ac tivated, am pu tat ing his legs. The vic tim bled

to death be fore he could be re moved from

the ma chine [Col o rado De part ment of Public Health and En vi ron ment 1994].

Case No. 4— Un con trolled

Po ten tial En ergy

The 32-year-old owner of a heavy equipment main te nance busi ness died af ter a

wheel and tire as sem bly ex ploded dur ing

re pair work. The vic tim was re mov ing the

as sem bly from a test roller when it exploded and struck him with the fly ing split

rim of the wheel.

The test roller was a large, two-wheeled

cart that car ried about 60,000 pounds of

con crete weights. The roller was used in

high way con struc tion to test road sur faces

for proper com pac tion.

The vic tim had been work ing as a sub contrac tor to re pair the wheel and tire as sembly, which had been smok ing ear lier in the

day and was be lieved to be rub bing against

the con crete weights. The as sem bly con -

sisted of a two-piece out side rim and an inside ring re tainer that was held to gether

and mounted on the axle by 20 wheel bolts

and nuts. Nor mal air pres sure for the mounted

tire was 70 psi.

The vic tim raised and blocked the roller.

With out dis charg ing the air from the tire

and us ing no per sonal pro tec tive equipment, he be gan to re move the wheel nuts

us ing a pneu matic im pact wrench. He had

no train ing or ex pe ri ence with this type of

work or in the ser vic ing of this type of

wheel. He did not re al ize that only some of

the bolts held the wheel tire as sem bly to

the axle. The re main der held the outer half

of the rim to the in side half, se cur ing the tire

to the wheel. As the vic tim re moved the

nine teenth wheel nut, the pres sur ized air in

the tire dis charged ex plo sively, caus ing the

split rim to fly off the wheel and strike him.

He died from ce re bral con tu sions and lac -

er a tions [Min ne sota De part ment of Health

1992].

Case No. 5— Uncontrolled Ki netic

and Ther mal En ergy

A 33-year-old jan i to rial worker died af ter

he was trapped in side a linen dryer at a

hos pi tal laun dry while clean ing plas tic

debris from the in side of the dryer drum.

The clean ing task (which usu ally took

15 min utes to an hour) in volved prop ping

open the door to the dryer with a piece of

wood and en ter ing the 4- by 8-foot dryer

drum. The melted de bris was re moved by

scrap ing and chis el ing it with screw driv ers

and chis els. The dryer was part of an au tomated sys tem that de liv ered wet laun dry

from the washer through an over head

Haz ard ous En ergy 5
conveyor to the dryer, where it was dried

during a 6-minute cy cle with air tem per atures of 217E to 230EF. The sys tem con trol

panel was equipped with an er ror light that

was ac ti vated if the dryer door was open,

in di cat ing that the dryer was out of ser vice.

On the night of the in ci dent, the vic tim

propped the door open and en tered the

dryer drum with out de-energizing or

locking out the dryer. He be gan to clean

the inside of the drum. Al though the er ror

light had been ac ti vated when the door

was propped open, the sig nal was

misinterpreted by a coworker, who restarted

the sys tem. When the sys tem was restarted, the over head con veyor de liv ered a

200-pound load of wet laun dry to the

dryer— knock ing out the wooden door prop,

trap ping the vic tim in side, and automatically 

start ing the dry ing cy cle. The victim remained trapped in side un til the cy cle was

com pleted and was dis cov ered when the

load was dis charged from the dryer. He

died thirty min utes later of se vere burns

and blunt head trauma [Mas sa chu setts

De part ment of Pub lic Health 1992].

CON CLU SIONS

Re view of the NIOSH FACE data in di cates

that three re lated fac tors con trib ute to in -

ju ries and deaths that oc cur when work ers

per form in stal la tion, main te nance, service,

or re pair work near haz ard ous energy

sources:

• Fail ure to com pletely de-energize, iso -

late, block, and/or dis si pate the hazard ous en ergy source

• Fail ure to lockout and tagout en ergy

con trol de vices and iso la tion points af -

ter the haz ard ous en ergy source has

been de-energized

•Fail ure to ver ify that the haz ard ous en -

ergy source was de-energized be fore

be gin ning work

These fa tal i ties could have been pre vented

if com pre hen sive haz ard ous en ergy control pro ce dures had been im ple mented

and fol lowed.

REC OM MEN DA TIONS

NIOSH rec om mends that em ploy ers imple ment the fol low ing steps to pre vent in juries and deaths of work ers who must work

with haz ard ous en ergy in their jobs:

1. Com ply with OSHA reg u la tions.

2. De velop and im ple ment a haz ard ous

en ergy con trol pro gram.

3. Iden tify and la bel all haz ard ous en ergy

sources.

4. De-energize, iso late, block, and/or dissi pate all forms of haz ard ous en ergy

be fore work be gins.

5. Es tab lish lock out/tagout pro grams that

— re quire work ers to se cure en ergy

con trol de vices with their own in divid u ally as signed locks and

keys— only one key for each lock

the worker con trols;‡

‡Use of mas ter keys should be re served for unusual cir cum stances when the worker is ab sent

from the work place. How ever, if mas ter keys are

nec es sary, keep them un der su per vi sory con trol.

List the proper pro ce dures for us ing them in the

writ ten pro gram for con trol ling haz ard ous en ergy.

6 Haz ard ous En ergy
— re quire that each lock used to se -

cure an en ergy con trol de vice be

clearly la beled with du ra ble tags to

iden tify the worker as signed to the

lock;

— make sure that the worker who in -

stalls a lock is the one who removes it af ter all work has been

com pleted; and

— if work is not com pleted when the

shift changes, work ers ar riv ing on

shift should ap ply their locks

before de part ing work ers re move

their locks.

6. Ver ify by test and/or ob ser va tion that

all en ergy sources are de-energized

be fore work be gins.

7. In spect re pair work be fore re ac ti vat ing

the equip ment.

8. Make sure that all work ers are clear of

dan ger points be fore re-energizing the 

sys tem.

9. Train ALL work ers in the ba sic concepts of haz ard ous en ergy con trol.

10. In clude a haz ard ous en ergy con trol

pro gram with any con fined-space en -

try pro gram.

11. En cour age man u fac tur ers to de sign

ma chines and sys tems that make it

easy to con trol haz ard ous en ergy.

These rec om men da tions are de scribed in

more de tail in the fol low ing sec tions.

1. Com ply with OSHA reg u la tions.

Em ployers and work ers must com ply with

OSHA reg u la tions for con trol ling haz ardous

en ergy dur ing main te nance and in stallation

work (see 29 CFR 1910.146, 1910.147,

1910.177, 1910.178, 1910.179, 1910.181,

1910.213, 1910.217, 1910.218, 1910.261,

1910.262, 1910.263, 1910.265, 1910.269,

1910.272, 1910.305, 1910.306, 1910.333,

1926.416, and 1926.417). OSHA standards and accepted safe work prac tices

require em ploy ers to en sure that all haz ardous en ergy sources are de-energized before work be gins. If these sources can not be

de-energized, OSHA re quires em ploy ers to

pro tect work ers with in su la tion, guard ing,

and ap pro pri ate per sonal pro tec tive

equip ment.

2. Im ple ment a haz ard ous en ergy

con trol pro gram.

Em ployers should de velop and im ple ment

a writ ten haz ard ous en ergy con trol program that, at a min i mum,

— de scribes safe work pro ce dures,

— es tab lishes for mal lock out/tagout

pro ce dures,

— trains all em ploy ees in the pro gram,

and

— en forces the use of the pro ce dures

(in clud ing dis ci plin ary ac tion for

fail ure to fol low them).

Haz ard ous en ergy con trol pro grams

should out line the fol low ing safe work

prac tices:

• Iden tify tasks that may ex pose work ers

to haz ard ous en ergy.

• Iden tify and de-energize all haz ard ous

en ergy sources, in clud ing those in ad -

ja cent equip ment.

Haz ard ous En ergy 7
• Lock out and tagout all en ergy-isolating

de vices to pre vent in ad ver tent or un autho rized re ac ti va tion or startup.

• Iso late, block, and/or dis si pate all haz -

ard ous sources of stored or re sid ual

en ergy, in clud ing those in ad ja cent

equip ment.

• Be fore be gin ning to work, ver ify en ergy

iso la tion and de-energization, in cluding that in ad ja cent equip ment or energy sources.

• Af ter work is com plete, ver ify that all

per son nel are clear of dan ger points

be fore re-energizing the sys tem.

Haz ard ous en ergy con trol among work

groups must be co or di nated when mul ti ple

em ploy ers are in volved in large pro jects

and when shift changes oc cur dur ing such

ac tiv i ties. Out side con trac tors should work

with the fa cil ity owner to make sure that an

ad e quate haz ard ous en ergy con trol program is im ple mented spe cif i cally for contract work ers.

3. Iden tify and la bel all haz ard ous

en ergy sources.

Em ployers should use jobsite sur veys to

en sure that all haz ard ous en ergy sources

(in clud ing those in ad ja cent equip ment)

are iden ti fied be fore be gin ning any installation, main te nance, ser vice, or re pair

tasks. Haz ard ous en ergy in cludes me chani cal mo tion, po ten tial or stored en ergy, elec -

tri cal en ergy, ther mal en ergy, and chem i cal

re ac tions. En ergy-isolating de vices such as 

breaker pan els and con trol valves should

be clearly la beled [NIOSH 1983].

4. De-energize, iso late, block, and/or dis -

si pate all forms of haz ard ous en ergy.

All forms of haz ard ous en ergy should be

de-energized, iso lated, blocked, and/or

dis si pated be fore work ers be gin any in stalla tion, main te nance, ser vice, or re pair

work. The method of en ergy con trol depends on the form of en ergy in volved and

the avail able means to con trol it. En ergy is 

con sid ered to be iso lated or blocked

when its flow or use can not oc cur

[NIOSH 1983].

To iso late or block en ergy, take the fol lowing steps:

• Dis con nect or shut down en gines or

mo tors that power me chan i cal sys tems.

• De-energize elec tri cal cir cuits by discon nect ing the power source from the

cir cuit.

• Block fluid (gas, liq uid, or va por) flow in

hy drau lic, pneu matic, or steam systems by us ing con trol valves or by cap -

ping or blank ing§ the lines.

• Block ma chine parts against mo tion

that might re sult from grav ity (fall ing).

Some forms of en ergy must also be dis sipated af ter a sys tem has been

de-energized. Sys tem com po nents such

as elec tri cal ca pac i tors, hy drau lic ac cu mula tors, or air res er voirs may re tain suf fi cient

en ergy to cause se ri ous in jury or

death— even though the com po nent has

been de-energized, iso lated, or blocked

from the sys tem and locked out.

En ergy can be dis si pated by tak ing the fol -

low ing steps:

•Vent flu ids from pres sure ves sels, tanks,

or ac cu mu la tors un til in ter nal pres sure

§

Lines can be blanked by in sert ing a solid plate be -

tween the flanges of a joint.

8 Haz ard ous En ergy
is at at mo spheric lev els. How ever, do

not vent ves sels or tanks con tain ing

toxic, flam ma ble, or ex plo sive sub stances

di rectly to the at mo sphere.

• Dis charge ca pac i tors by ground ing.

• Re lease or block springs that are under ten sion or com pres sion.

• Dis si pate in er tial forces by al low ing

the sys tem to come to a com plete

stop af ter the ma chine or equip ment

has been shut down and iso lated from

its en ergy sources.

5. Es tab lish lock out/tagout pro grams

re quir ing in di vid u ally as signed

locks and keys to se cure en ergy

con trol de vices.

Lock out/tagout pro grams should be based

on the prin ci ple of only one key for each

lock the worker con trols.

** This means the

fol low ing:

— Workers are as signed in di vid ual

locks op er a ble by only one key for

use in se cur ing en ergy con trol de -

vices (breaker pan els, con trol

valves, man ual over ride switches,

etc.).

— Each worker main tains cus tody of

the key for each of his or her assigned locks.**

**Use of mas ter keys should be re served for unusual cir cum stances when the worker is ab sent

from the work place. How ever, if mas ter keys are

nec es sary, keep them un der su per vi sory con trol.

List the proper pro ce dures for us ing them in the

writ ten pro gram for con trol ling haz ard ous en ergy.

— Each lock is la beled with a du ra ble

tag or other means that iden ti fies

its owner.

— When work is per formed by more

than one worker, each worker

applies his or her own lock to the

energy-securing de vice. Scis sorstype hasps made of hard ened

steel are avail able to fa cil i tate the

use of more than one lock to secure an en ergy con trol de vice.

— All de-energized cir cuits and sys -

tems are clearly la beled with du rable tags.

— The worker who installs a lock is

the one who re moves it af ter all

work has been com pleted [NIOSH

1988].

— If work is not com plete when the

shift changes, work ers ar riv ing on

shift ap ply their locks be fore de parting work ers re move their locks.

Be cause tags can be eas ily re moved, they

are not a sub sti tute for locks. Workers are

saf est with a pro gram that uses both locks

and warn ing tags to pre vent sys tems from

be ing in ad ver tently re-energized [NIOSH

1988].

6. Ver ify that all en ergy sources are

de-energized be fore work be gins.

Em ployers should es tab lish and en force

company pol i cies re quir ing work ers to

verify that all en ergy sources are

de-energized be fore work be gins. This ver i fica tion should en sure that all en ergy sources

(in clud ing stored en ergy) are con trolled

(that is, de-energized, iso lated, blocked,

and/or dis si pated) be fore work be gins. Ap -

pro pri ate test ing equip ment should be re -

quired as needed.

Haz ard ous En ergy 9
 7. In spect re pair work be fore re -

energizing the equip ment.

To en sure that equip ment will op er ate as

ex pected when it is re-energized, employers should re quire qual i fied per sons to

in spect com pleted in stal la tion, main tenance, ser vice, or re pair work. The in spection should ver ify that in stal la tion, re pairs,

and mod i fi ca tions were per formed correctly and that the cor rect re place ment

parts were used. When equiv a lent or up -

dated parts must be sub sti tuted for orig i nal

parts, the sys tem may need to be mod i fied.

Re-energized equip ment should be closely

mon i tored for sev eral op er at ing cy cles to

en sure that it is func tion ing cor rectly and

safely.

8. Make sure that all per sons are clear

of dan ger points be fore re-energizing

the sys tem.

Em ployers should de velop pro ce dures to

ver ify that all per sons are clear of dan ger

points be fore re-energizing the sys tem.

Locks and tags should be re moved only by

the work ers who in stalled them— and only

af ter work ers have been cleared from the

dan ger points. This may re quire vi sual in -

spec tions and searches of ar eas around

ma chin ery or elec tri cal cir cuits to as sure

that work ers will not be ex posed to the re -

lease of haz ard ous en ergy when equipment is re-energized. Workers should be

in formed about im pend ing equip ment

start-up with warn ing de vices they can see

and hear. Such de vices will help as sure

that work ers are clear be fore equip ment is

re-energized.

9. Train work ers in the ba sic con cepts

of haz ard ous en ergy con trol.

Em ployers should train ALL work ers in

the ba sic con cepts of haz ard ous en ergy

con trol, in clud ing en ergy iso la tion,

lock ing and tag ging of con trol de vices, ver -

i fy ing de-energization, and clear ing dan ger

points be fore re-energizing equip ment.

Workers whose du ties in volve in stal la tion,

main te nance, ser vice, or re pair work

should be trained in the de tailed con trol

pro ce dures re quired for their par tic u lar

equip ment. This train ing should en able

work ers to iden tify tasks that might ex pose

them to haz ard ous en ergy and the ef fective meth ods for its con trol.

10. In clude a haz ard ous en ergy con trol

pro gram with any con fined-space

en try pro gram.

When work re quires en try into con fined

spaces such as util ity vaults or tanks, em -

ploy ers should in cor po rate a haz ard ous

en ergy con trol pro gram as part of their

confined-space en try program— according 

to OSHA stan dards [29 CFR 1910.146 and

1910.147] and pub lished NIOSH guidelines [NIOSH 1979, 1987].

11. De sign ma chines and sys tems that

make it easy to con trol haz ard ous

en ergy.

Em ployers should en cour age man u fac turers to de sign con trol valves, switches, and

equip ment that are easy to ac cess and

lock out.

AC KNOWL EDG MENTS

Prin ci pal con tri bu tors to this Alert were

Paul Moore and Tim Pizatella of the NIOSH

Division of Safety Re search (DSR). In jury

data were pro vided by the Health and

Safety De part ment, In ter na tional Un ion,

United Auto Workers (UAW). Cases presented in this Alert were con trib uted by

Georjean Madery, for merly of the Min nesota De part ment of Health; Lyle McKenzie,

Col o rado De part ment of Health; and Jon

10 Haz ard ous En ergy
Lifvergren, for merly of the Mas sa chu setts

De part ment of Health. Steph a nie Pratt,

DSR, pro vided data anal y sis, and Larry

Reed, Di vi sion of Phys i cal Sci ences and

Engineering, pro vided many help ful com -

ments and sug ges tions. Dwayne Smith,

for merly of DSR, pro vided the first work ing

draft of this Alert.

Please di rect com ments, ques tions, or re -

quests for ad di tional in for ma tion to the fol -

low ing:

Dr. Nancy A. Stout, Di rec tor

Di vi sion of Safety Re search

Na tional In sti tute for Oc cu pa tional Safety

 and Health

1095 Willowdale Road

Morgantown, West Vir ginia 26505–2888

Tele phone: 304–285–5894; or call

1–800–35–NIOSH (1–800–356–4674).

We greatly ap pre ci ate your help in pro tecting the safety and health of U.S. work ers.

Linda Rosenstock, M.D., M.P.H.

Di rec tor, Na tional In sti tute for

 Oc cu pa tional Safety and Health

Cen ters for Dis ease Con trol and

 Pre ven tion

REF ER ENCES

CFR. Code of Fed eral reg u la tions. Wash -

ing ton, DC: U.S. Gov ern ment Print ing Of -

fice, Of fice of the Fed eral Reg is ter.

Col o rado De part ment of Pub lic Health and

En vi ron ment [1994]. Thirty-eight-year-old

re cy cling tech ni cian dies as a re sult of in juries sus tained when he fell into a card board

com pac tor. Den ver, CO: Col o rado De partment of Health and En vi ron ment, Col o rado

Fa tal ity As sess ment and Con trol Eval u ation (FACE) Re port No. 94CO029.

Mas sa chu setts De part ment of Pub lic

Health [1992]. Cus to dian dies in a con fined

space in a hos pi tal laun dry. Boston, MA:

Mas sa chu setts De part ment of Pub lic

Health, Mas sa chu setts Fa tal ity As sessment and Con trol Eval u a tion (MA FACE)

Re port No. 91–02.

Min ne sota De part ment of Health [1992].

Owner of heavy equip ment main te nance

busi ness dies af ter be ing struck by an

exploding split rim of a test roller tire.

Minneapolis, MN: Min ne sota De part ment of 

Health, Min ne sota Fa tal ity As sess ment and 

Con trol Eval u a tion (MN FACE) Re port

No. MN9208.

NIOSH [1979]. Cri te ria for a rec om mended

stan dard: work ing in con fined spaces.

Morgantown, WV: U.S. De part ment of

Health, Ed u ca tion, and Wel fare, Pub lic

Health Ser vice, Cen ter for Dis ease Control, Na tional In sti tute for Oc cu pa tional

Safety and Health, DHEW (NIOSH) Pub lica tion No. 80–106.

NIOSH [1983]. Guide lines for con trol ling

haz ard ous en ergy dur ing main te nance

and ser vic ing. Morgantown, WV: U.S. De -

part ment of Health and Hu man Ser vices,

Pub lic Health Ser vice, Cen ters for Dis ease

Con trol, Na tional In sti tute for Oc cu pa tional

Safety and Health, DHHS (NIOSH) Pub lica tion No. 83–125.

NIOSH [1987]. A guide to safety in con fined

spaces. Morgantown, WV: U.S. De partment of Health and Hu man Ser vices, Pub -

lic Health Ser vice, Cen ters for Dis ease

Con trol, Na tional In sti tute for Oc cu pa tional

Haz ard ous En ergy 11
Safety and Health, DHHS (NIOSH) Pub lica tion No. 87–113.

NIOSH [1988]. NIOSH tes ti mony on the

Oc cu pa tional Safety and Health Ad min istra tion’s pro posed rule on the con trol of

haz ard ous en ergy sources (lock out/tagout),

Sep tem ber 8, 1988, OSHA Docket

No. S–012A. Cincinnati, OH: U.S. De partment of Health and Hu man Ser vices, Pub -

lic Health Ser vice, Cen ters for Dis ease

Con trol, Na tional In sti tute for Oc cu pa tional

Safety and Health.

NIOSH [1994]. Jour ney man wireman elec -

tro cuted af ter con tact ing en er gized

switchgear com po nents at power

plant— West Vir ginia. Morgantown, WV:

U.S. De part ment of Health and Hu man

Ser vices, Pub lic Health Ser vice, Cen ters

for Dis ease Con trol and Pre ven tion,

Na tional In sti tute for Oc cu pa tional Safety

and Health, Fa tal ity As sess ment and Con -

trol Eval u a tion (FACE) Re port No. 94–10.

NIOSH [1995]. La borer fa tally in jured while

clean ing con crete mixer— Ten nes see.

Morgantown, WV: U.S. De part ment of

Health and Hu man Ser vices, Pub lic Health 

Ser vice, Cen ters for Dis ease Con trol and

Pre ven tion, Na tional In sti tute for Oc cu pational Safety and Health, Fa tal ity As sessment and Con trol Eval u a tion (FACE)

Re port No. 95–12.

UAW [1997]. An anal y sis of trends in fa tal

in ju ries re lated to lock-out fail ure in

UAW-represented worker pop u la tions.

Detroit MI: In ter na tional Un ion, United Au -

to mo bile, Aero space and Ag ri cul tural Imple ment Workers of Amer ica— UAW, UAW

Health and Safety De part ment.

12 Haz ard ous En ergy
Preventing Worker Deaths from Uncontrolled Release of

Electrical, Mechanical, and Other Types of Hazardous Energy

Take the fol low ing steps to pro tect your self if you

in stall or ser vice equip ment and sys tems:

•Fol low OSHA reg u la tions.

•Iden tify and la bel all sources of haz ard ous

en ergy.

•Be fore be gin ning work, do the fol low ing:

1. De-energize all sources of hazardous

energy:

— Dis con nect or shut down en gines or

mo tors.

— De-energize elec tri cal cir cuits.

— Block fluid (gas or liq uid) flow in

hy drau lic or pneu matic sys tems.

— Block ma chine parts against mo tion.

2. Block or dissipate stored energy:

— Dis charge ca pac i tors.

— Re lease or block springs that are

un der com pres sion or ten sion.

— Vent flu ids from pres sure ves sels,

tanks, or ac cu mu la tors— but never

vent toxic, flam ma ble, or ex plo sive

sub stances di rectly into the atmosphere.

3. Lockout and tagout all forms of

hazardous energy— including electrical

breaker panels, control valves, etc.

4. Make sure that only one key exists for

each of your assigned locks and that

only you hold that key.

5. Verify by test and/or observation that

all energy sources are de-energized.

6. Inspect repair work before removing

your lock and activating the equipment.

7. Make sure that only you remove your

assigned lock.

8. Make sure that you and your coworkers are clear of danger points

before re-energizing the system.

•Par tic i pate in all train ing pro grams of fered by

your em ploy ers.

Please tear out and post. Dis trib ute cop ies to work ers. See back of sheet to or der com plete Alert.

WARNING!

Workers who install or service equipment and systems may be

injured or killed by the uncontrolled release of hazardous energy.

Re printed with per mis sion of IDESCO Cor po ra tion, © 1999.

Only the worker who in stalls a lock and tag should

re move them af ter work is com plete and in spected.
For ad di tional in for ma tion, see NIOSH Alert: Pre venting Worker

In juries and Deaths from Haz ard ous En ergy Re lease [DHHS

(NIOSH) Pub li ca tion No. 99–110. Sin gle cop ies of the Alert are available free from the fol low ing:

Na tional In sti tute for Oc cu pa tional Safety and Health

Pub li ca tions Dis sem i na tion

4676 Co lum bia Park way

Cincinnati, OH 45226–1998

Fax num ber: (513) 533–8573

Phone num ber: 1–800–35–NIOSH (1–800–356–4674)

E-mail: pubstaft@cdc.gov

U.S. De part ment of Health and Hu man Ser vices

Pub lic Health Ser vice

Cen ters for Dis ease Con trol and Pre ven tion

Na tional In sti tute for Oc cu pa tional Safety and Health