Subpart S Electrical

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Subpart SElectrical

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Subpart S

• Electrical Standards

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1910.301Introduction

• (a) Design Safety Standards for Electrical
  Systems
• 1910.302-308
• 1910.309-330 (future design)
• Safety-Related Work Practices
• 1910.331-360
• (c) Safety-Related Maintenance Requirements
• 1910.361-380
• Safety Requirements for Special Equipment
• 1910.381-399
• (e) Definitions - 1910.399

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1910.302 - ElectricUtilization Systems

• (a) Scope
• (1) Coverage
• Equipment installations used within or on
  buildings,
• structures, and other premises, including

• Industrial substations
• Conductors connecting supply of electricity
• Other outside conductors on premises

• Yards
• Carnivals
• Parking/Other lots
• Mobile homes
• Recreational vehicles

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1910.302 - ElectricUtilization System (Cont)
(a)(2) Not Covered

• Ship installations
• Watercraft
• Railroad rolling stock
• Aircraft
• Automotive vehicles other than RVs

• Railroad generating, transforming, transmitting
  or distribution of power
• Communication equipment
• Electric utilities

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1910.302 - ElectricUtilization Systems (Cont)
(b) Extent of application (1) Requirements apply
to all electrical installations (regardless of
when designed and installed) in sections

• 1910.303(b)-(f)
• 1910.303(g)(2)
• 1910.304(e)(1)(i)
• 1910.304(e)(1)(iv)-(v)
• 1910.304(f)(1)(ii)-(v)

• 1910.304(f)(3)-(4)
• 1910.304(f)(5)(iv)(a)-(d)
• 1910.304(f)(5)(v)-(vi)
• 1910.304(f)(6)(i)
• 1910.305(g)(1)(i)-(iii)
• 1910.305(g)(2)(ii)-(iii)

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1910.302 - ElectricUtilization Systems (Cont)

• (b)(2) Every system/equipment installed after
  March 15, 1972, and major replacements,
  modifications, repairs, or rehabilitation after
  March 15, 1972 of older systems, shall comply
  with 1910.302-308.

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1910.303General Requirements

• (a) Only approved conductors and equipment
• (b) Examination, installation and use of
  equipment
• (1) Electrical equipment free from recognized
  hazards likely to cause death/serious physical
  harm to employees 5(a)(1)
• (2) Installation and use - listed or labeled
  equipment shall be used or installed in
  accordance with any instructions included in the
  listing or labeling

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1910.303 - GeneralRequirements (Cont)

• (c) Splicing
• Conductors joined or spliced by
• Brazing
• Welding
• Soldering
• Covered by insulation
• (d) Arcing parts shall be enclosed

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1910.303 - General Requirements (Cont)

• (e) Marking - Electrical equipment shall be
  marked
• Manufactures name
• Trademark
• Voltage
• Current
• Wattage
• Durable markings

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1910.303 - GeneralRequirements (Cont)

• (f) Identification of disconnecting means and
  circuits for the following shall be legibly
  marked and durable
• Motors
• Appliances
• Each service
• Each feeder
• Each branch circuit

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1910.303 - GeneralRequirements (

• (g) 600V or less
• (1)(i) Working space about electrical equipment
  (Table S-1)
• (ii) Clear spaces working space/no storage
• (2) Guarding of live parts
• 50V or more guarded against accidental contact
  by
• Approved cabinets/enclosures
• Location in room/vault
• Partitions/screens (only qualified persons)
• Location on balcony, gallery, platform
• Elevation 8 ft. or more above floor

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1910.303 - GeneralRequirements (Cont)

• (h) Over 600V
• (3) Workspace about equipment
• See Table S-2

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1910.304 - Wiring Designand Protection

• (a) Use/identification of grounded/grounding
  conductors
• (1) Distinguishable from other conductors
  (Usually green)
• (2) Polarity of connections
• No reverse polarity on leads/terminals
• (b) Branch circuits
• (1) Reserved
• (2) Outlet devices
• Ampere rating not lt load served

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1910.304 - Wiring Designand Protection (Cont)

• (c) Outside conductors - 600V or lt
• (1) Conductors on poles - horizontal climbing
  space not less than
• (i) Power conductors below communication
  conductors - 30
• (ii) Power conductors alone or above
  communication conductors -
• 300V or less - 24
• gt 300V - 30
• (iii) Communication conductors below power
  conductors
• 300V or less - 24
• 300V or more - 30

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1910.304 - Wiring Designand Protection (Cont)

• (c)(2) Minimum clearances from ground
• (i) 10 ft. - above finished grade, sidewalks,
  platforms
• (ii) 12 ft. - over areas subject to vehicle
  traffic (not truck traffic)
• (iii) 15 ft. - over areas subject to truck
  traffic
• (iv) 18 ft. - over public streets, alleys, roads,
  driveways
• (3) Clearance from building openings - conductors
  shall have clearance of at least 3 ft. from
  windows, porches, doors, and fire escapes

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1910.304 - Wiring Designand Protection (Cont)

• (c)(4) Clearance over roofs
• Conductors shall have clearance of at least 8 ft.
  from highest point of roofs over which they pass
• Exceptions
• (i) Voltage between conductors
• 300V or lt and roof slope 4 in 12--clearance from
  roofs 3 ft. or,
• (ii) Voltage between conductors
• 300V or lt and conductors do not pass over more
  than 4 ft. of overhang portion of roof--clearance
  from roofs 18

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1910.304 - Wiring Designand Protection (Cont)

• (d) Services
• (1) Disconnecting means
• (i) General
• Shall be provided to disconnect conductors (in
  buildings or structures) from service entrance
  conductors
• Indicators for open and closed positions
• Readily accessible location nearest point of
  entrance of the service-entrance conductors

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1910.304 - Wiring Designand Protection (Contd)

• (d)(2) Services gt 600V
• (i) Guarding -- Service entrance conductors
  installed as open wires accessible only to
  qualified persons
• (ii) Warning signs -- High voltage signs for
  other than qualified employees

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1910.304 - Wiring Designand Protection (Cont)

• (e) Overcurrent protection
• (1) Circuits 600V or lt
• (i) Protection of conductors and equipment from
  overcurrent
• (ii) Grounded conductors
• Except for motor running overload protection, no
  interruption of grounded conductors, unless all
  circuit conductors opened simultaneously
• (iii) Disconnection of fuses and thermal cutouts
• Except service fuses, all fuses, thermal cutouts,
  circuits gt 150V to ground

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1910.304 - Wiringand Protection (Cont)

• (e)(1)(iv) Location in or on premises
• Overcurrent devices readily building management
  personnel
• (v) Arcing/Suddenly moving parts
• Fuses/circuit breakers located or shielded so not
  to cause burns or injuries
• (vi) Circuit breakers shall indicate
• Open (Off)
• Closed (On)

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1910.304 - Wiring Designand Protection (Cont)

• (f) Grounding
• (1) Systems to be grounded
• (i) All 3 wire DC systems - neutral conductor
  grounded
• (ii) 2 wire DC systems over 50V to 300V between
  conductors - grounded
• (2) Conductors to be grounded
• AC systems - identified

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1910.304 - Wiring Designand Protection (Cont)

• (f)(3) Grounding connections
• (4) Grounding path
• Path to ground from circuits, equipment,
  enclosures - permanent and continuous

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1910.304 - Wiring Designand Protection (Con)

• (f)(5) Supports, enclosures and equipment to be
  grounded
• (i) Metal cable trays, metal raceways, metal
  conductor enclosures shall be grounded
• (v) Equipment connected by cord and plug
• Non-current carrying metal parts of cord and plug
  connected equipment which may be energized shall
  be grounded IF
• in hazardous locations
• operated at gt 150V
• of types such as refrigerators, A.C., hand-held
  motor tools, tools used in wet locations,
  portable hand lamps

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1910.305 - Wiring Methods,Components and
Equipment

• (a) Wiring methods
• (1) General requirements
• (i) Metal raceways, cable armor, and other metal
  enclosures shall be metallically joined together
  into continuous electric conductor and be
  connected to all boxes, fittings, cabinets for
  effective electrical continuity

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1910.305 - WiringMethods, etc. (Cont)

• (a)(2) Temporary wiring
• (i) Uses permitted - 600V or lt
• (A) Remodeling, maintenance, repair, demolition
• (B) Experimental or development work
• (C) Period not gt 90 days for Christmas lighting,
  etc.

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1910.305 - WiringMethods, etc. (Cont)

• (b)(1) Conductors entering cabinets, boxes,
  fittings
• Protected from abrasion
• Openings effectively closed
• (2) Covers and canopies
• Pull boxes, junction boxes, fittings provided
  with approved covers

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1910.305 - WiringMethods, etc. (Cont)

• (c) Switches
• (1) Knife - Single-throw type
• Blades dead - switch open position
• Placed so gravity will not tend to close switch
• (2) Faceplates for flush-mounted snap switches

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1910.305 - WiringMethods, etc. (Cont)

• (d) Switchboards and panel boards
• Live parts located in dry locations
• Accessible to qualified persons
• Panel boards shall be mounted in cabinets, cutout
  boxes or enclosures and dead front

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1910.305 - WiringMethods, etc. (Cont)

• (e) Enclosures for damp or wet locations
• (1) Cabinets, cutout boxes, fittings, boxes,
  panel board enclosures installed to prevent
  moisture in enclosures
• Wet locations - weatherproof enclosures
• (2) Weatherproof enclosures for
• Switches, circuit breakers, switchboards in wet
  locations
• (f) Conductors for general wiring shall be
• Insulated
• Approved for voltage, operating temperature,
  location of use
• Distinguishable by appropriate color or other
  suitable means

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1910.305 - WiringMethods, etc. (Cont)

• (g) Flexible cords and cables
• (1) Approved usage
• Pendants
• Wiring of fixtures
• Connection of portable lamps and appliances
• Elevator cables
• Wiring of cranes and hoists
• Connection of stationary equipment to facilitate
  interchange

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1910.305 - WiringMethods, etc. (Cont)

• (g)(1)(iii) Flexible cords may not be used
• As a substitute for fixed wiring
• Where run through holes in walls, ceilings,
  floors
• Where run through doorways, windows, openings
• Attached to building surfaces
• Concealed behind walls, ceilings, floors

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1910.305 - WiringMethods, etc. (Cont)

• (g)(2) Identification, splices and terminations
• (i) Conductors - Flexible cords and cables used
  as grounded conductor or equipment grounding
  conductor shall be distinguishable.
• Types SJ, SJO, SJT, SJTO, S, SO, ST, and STO
  shall be durable marked with
• Type designation
• Size
• Number of conductors

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1910.305 - WiringMethods, etc. (Cont)

• (g)(2)(ii) Flexible cords
• Used only in continuous lengths (no
  splicing/taping)
• Hard surface 12 or larger may be repaired, if
  splicing retains insulation and sheath properties
• (iii) Flexible cords - connected to devices and
  fittings to provide strain relief
• (j) Equipment for general use
• (1)(i) Lighting fixtures, lampholders, lamps,
  receptacles and rosettes
• No live parts exposed unless 8 ft. above

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1910.306 - Specific PurposeEquipment and
Installations

• (a) Electric signs and outline lighting
• (1) Disconnecting means (electronic/electromechani
  cal controllers) -
• Capable of being locked in open position

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1910.306 - Specific PurposeEquipment (Cont)

• (b) Cranes/Hoists
• (1) Disconnecting means
• Between runway contact conductors and power
  supply
• Another means, capable of being locked in open
  position, shall be provided
• (2) Control
• Limit switch to prevent load block passing safe
  upper limit
• (3) Clearance for working space/access to live
  parts - 2 ft. 6 in.

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1910.306 - Specific PurposeEquipment (Cont)

• (c) Elevators, dumbwaiters, escalators, moving
  walks
• (1) Disconnecting means - Have single
  disconnecting means (ungrounded main power
  conductors)
• (2) Warning signs
• (3) Control panels
• Cabinets with doors
• Capable of being locked closed

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1910.306 - Specific PurposeEquipment (Cont)

• (d) Electric welders/disconnection means
• (1) In supply circuit for
• Each motor - generated arc welder
• Each AC transformer
• Each DC rectifier arc welder
• (2) Switch/circuit breaker provided so resistance
  welders and control equipment isolated from
  supply circuit

Not equipped with disconnect in welder
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1910.306 - Specific PurposeEquipment (Cont)

• (e) Data processing equipment
• Disconnecting means to all
• Electronic equipment in data processing and
  computer rooms
• Air conditioning system

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1910.306 - Specific PurposeEquipment (Cont)

• (f) X-ray equipment - other than medical/dental
  use
• (1) Disconnecting means
• (i) In supply circuit
• Readily accessible from X-ray control
• (ii) High voltage switch or equivalent
• (2) Control
• (i) Radiographic/fluoroscopic types
• Effectively enclosed/interlocks
• (ii) Diffraction and irradiation types
• Energy indication

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1910.306 - Specific PurposeEquipment (Cont)

• (g) Induction/dielectric heating equipment
• (1) Scope
• Industrial
• Scientific
• (2) Guarding/grounding
• (i) Enclosures
• (ii) Panel controls
• (iii) Access to internal equipment
• (iv) Warning labels - Danger
• (v) Work applicator shielding
• (vi) Disconnecting means

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1910.306 - Specific PurposeEquipment (Cont)

• (h) Electrolytic cells
• (1) Scope
• (2) Definitions
• Cell line - assembly of electrically
  interconnected electrolytic cells supplied by DC
  power
• Cell line attachments/auxiliary equipment
• Cell line working zone
• Electrolytic cells
• (3) Application
• (4) Disconnecting means
• (5) Portable electric equipment

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1910.306 - Specific PurposeEquipment (Cont)

• (h)(6) Power supply circuits and receptacles for
  portable electric equipment
• (7) Fixed/portable electric equipment
• (8) Auxiliary non-electric connections
• (9) Cranes/hoists

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1910.306 - Specific PurposeEquipment (Cont)

• (i) Electrically driven/controlled irrigation
  machines
• (1) Lighting protection
• (2) Disconnecting means
• (j) Swimming pools, fountains, similar
  installations
• (1) Scope
• (2) Lighting and receptacles
• (3) Cord/plug connected equipment
• (4) Underwater equipment
• (5) Fountains

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• Electrical Safety-Related Work Practices Standard
• 29 CFR 1910, Subpart S

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1910.331 - Scope

• Covers both qualified and unqualified persons
  working on, near or with electrical conductors
  and equipment.

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1910.331 - Scope

• Contains requirements for
• Working on or near electrical equipment
• Use of electrical protective equipment
• The safe use of electrical equipment

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1910.331 - Scope

• Does not cover work by qualified persons on
• Generation, transmission and distribution
  installations
• Communication installations
• Installations in vehicles
• Railway installations

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1910.332 - Training
Required for employees who face the risk of
electrical shock
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1910.332 - Content of Training

• Electrical safe work practices
• Other safe work practices necessary for safety

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1910.332 - Content of Training
Qualified persons shall also be trained in

• Distinguishing exposed live parts
• Determining normal voltage of parts
• Clearance distances and voltages

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1910.332 - Type of Training
Classroom or on the job, depth of training based
on risk
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1910.333 - Selection and Use of Work Practices
Safe work practices shall be used and
be consistent with the nature and extent of
the associated hazard.
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1910.333(a)(1) - Selection and Use of Work
Practices

• Live parts to which an employee may be exposed
  shall be de-energized before the employee works
  on or near them, unless de-energizing introduces
  additional or increased hazards or is infeasible
  due to equipment design or operational
  limitations.
• Live parts that operate at less than 50 volts to
  ground need not be de-energized if there will be
  no increased exposure to electrical burns or to
  explosion due to electrical arcs.

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1910.333(a)(2) - Selection and Use of Work
Practices

• If the exposed live parts are not de-energized,
  other safety-related work practices shall be used
  to protect employees who may be exposed to the
  electrical hazards involved.

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1910.333(b) - Working On or Near Exposed
De-energized Parts

• (2) While any employee is exposed to contact with
  parts of fixed electric equipment or circuits
  which have been de-energized, the circuits
  energizing parts shall be locked out or tagged
  out or both.

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1910.333(b) - Working On or Near Exposed
De-energized Parts

• (2)(ii)(B) The circuits and equipment to be
  worked on shall be disconnected from all electric
  energy sources.
• (2)(ii)(C) Stored electric energy which might
  endanger personnel shall be released.
• (2)(ii)(D) Stored non-electrical energy in
  devices that could reenergize electric circuit
  parts shall be blocked or relieved to the extent
  that the circuit parts could not be accidentally
  energized by the device.

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1910.333(c) - Working On or Near Exposed
Energized Parts

• (2) Only qualified persons may work on electrical
  circuit parts or equipment that have not been
  de-energized
• (3) If work is to be performed near overhead
  lines, the lines shall be de-energized and
  grounded, or other protective measures shall be
  provided before work is started

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1910.333(c)(3)Overhead Lines

• (ii) When a qualified person is working in the
  vicinity of overhead lines, the person may not
  approach or take any conductive object without an
  approved insulating handle closer to exposed
  energized parts than shown in Table S-5 unless
• (A) The person is insulated form the energized
  part
• (B) The energized part is insulated both from all
  other objects conductive objects
• (C) The person is insulated from all conductive
  objects

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1910.333(c)(3)(iii) - Vehicular and Mechanical
Equipment
(Near overhead power lines)

• Must be kept at least 10 ft away
• In transit, must be kept at least 4 ft. away
• Employees may not contact equipment if approach
  distances can be violated

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1910.333(c)(4) - Illumination

• (i) Employee may not enter spaces containing
  exposed energized parts, unless illumination is
  provided that enables the employees to perform
  the work safely.

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1910.333(c)(5) - Confined or Enclosed Spaces

• Employees working near exposed live parts shall
  be provided with and use protective shields,
  barriers or insulating materials in order to
  prevent inadvertent contact with live parts.

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1910.333(c)(6) - Conductive Materials and
Equipment

• Conductive material must be used in safe manner
• Safe work practices must be used when working
  with long, conductive objects

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1910.333(c)(7) - Portable Ladders

• Portable ladders shall be of nonconductive
  materials if they are used where the employee or
  the ladder could contact exposed energized parts.

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1910.333(c)(8)Conductive Apparel

• Conductive clothing and jewelry cannot be worn if
  they can come into contact with live parts

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1910.333(c)(9)Housekeeping Duties

• Adequate safety precautions and nonconductive
  cleaning materials must be used around live parts

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1910.333(c)(10)Interlocks

• Only a qualified person may temporarily defeat an
  interlock while working on equipment
• Equipment must be returned to its operating
  condition

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1910.334(a) - Portable Electrical Equipment

• Cannot staple cord in place
• Cannot lift or lower by cord
• Check cord for defects
• Cords to have proper grounding
• Cords must be approved for location
• Safe work practices must be in place before
  starting work

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1910.335 - Safeguards for Personnel Protection

• Employers must provide
• Employees must wear if exposed to hazards
• Must be maintained in a safe condition
• Non-conductive head protection must be worn

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1910.335(a)(2) - General Protective Equipment and
Tools

• (i) Appropriate insulated tools must be used
  around live parts
• (ii) Protective shields and barriers must be used
  around live parts if they can be contacted

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1910.335(b) - Alerting Techniques

• Safety signs, tags, barricades and sometimes
  attendants must be used to alert employees of
  electrical hazards

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