Protection From Electric Shock and Arc Flash
CPWR - The Center for Construction Research and Training
Summary Statement
Discussion of the electric hazards posed to electrical workers, describes the nature of the hazards and steps that can be taken to improve safety.
2003
About 50 electrical workers are killed in construction every year in the U.S. by electric current and many more are injured. Over half of the deaths are from working on energized ("live") electric circuits without proper protection - often when it was not necessary to work "live." At least one-third of the electrocutions occur at low voltage, under 600 volts. This paper discusses precautions for electricians, but does not cover electric utility work.
Electric hazards
Electricity-related hazards include electric shock and burns, arc-flash burns, arc-blast impacts, and falls.- Electric shock and burns. An electric shock occurs when electric current passes through your body. This can happen when you touch an energized part. If the electric current passes across the chest or head, you can be killed. At high voltages, severe burns can result.
- Arc-flash burns. An electric arc flash can occur if a conductive object gets too close to a high-amp current source or by equipment failure (for instance, while opening or closing disconnects). The arc can heat the air to temperatures as high as 35,000 F, and vaporize metal in the equipment. The arc flash can cause severe skin burns by direct heat exposure and by igniting clothing.
- Arc-blast impacts. The heating of the air and vaporization of metal creates a pressure wave that can damage hearing and cause memory loss (from concussion) and other injuries. Flying metal parts are also a hazard.
- Falls. Electric shocks and arc blasts can cause falls, especially from ladders or unguarded scaffolding.
Electric Safety Principles
Plan
every job. Decide on your approach and step-by-step procedures.
Write down first-time procedures. Discuss hazards and procedures
in a job briefing with your supervisor and other workers before
starting a job. Your employer should already have or develop a
permit system for working on live circuits, if a circuit must
be worked live.
You might need to work live to avoid interrupting life-support systems, deactivating emergency alarm systems, or shutting down ventilation equipment for hazardous locations, for instance. And de-energizing would not be practical during testing of live electric circuits or work on circuits that are part of a continuous process that cannot be completely shut down.
The most important principle of electric safety is, assume electric circuits are energized unless you make sure they are not. Test every circuit and conductor every time you work on them. The National Fire Protection Association lists six steps to ensure conditions for electrically safe work.**
Lockout/tagout program
Your employer should establish a written lockout/tagout program and train employees in the program. The program should cover planning for locating and labeling energy sources, identifying employees at risk, how and by whom the equipment is de-energized, releasing of stored energy, verifying that the circuit is de-energized and can't be restarted, voltage testing, grounding requirements, shift changes, coordination with other jobs in progress, a procedure for keeping track of all involved personnel, applying and removing lockout/tagout devices, return to service, and temporary re-energizing for testing/positioning. Lockout/tagout procedures should be developed for each machine or piece of equipment that will require servicing.
Lockout/tagout application. Each person who could be exposed to electric energy must be involved in the lockout/tagout process.
Complex lockout/tagout procedures. Special procedures are needed when there is more than one energy source, crew, craft, location, employer, way to disconnect, or lockout/tagout procedure - or work that lasts beyond one shift. In any of these cases, one qualified person should be in charge of the lockout/tagout procedure with full responsibility for ensuring all energy sources are under lockout/tagout and to account for all people on the job. There should be a written plan addressing the specific details and naming the person in charge.
Removal of lockout/tagout devices. Lockout and tagout devices should be removed only by the person installing them. If work is not completed when the shift changes, workers arriving on shift should apply their locks before departing workers remove their locks.
Return to service. Once work is completed and lockout/tagout devices removed, tests and visual inspection must confirm that all tools, mechanical restraints, electric jumpers, shorts, and grounds have been removed. Only then is it safe to re-energize and return to service. Employees responsible for operating the equipment and needed to safely re-energize it should be out of the danger zone before equipment is re-energized.
Temporary release. If the job requiring lockout/tagout is interrupted for testing or positioning equipment, follow the same steps as in return to service (above).
Live-work permit system
A live work permit should, at a minimum, contain this information:
The National Fire Protection Association defines three approach distances for shock hazards and one for arc flash.*** Electric shock (see table 1).
Remember, when you have de-energized the parts you are going to work on, but are still inside the flash protection boundary for nearby live exposed parts: If the parts cannot be de-energized, you must use barriers such as insulated blankets to protect against accidental contact or you must wear proper PPE.
Proper Personal Protective Equipment
When working on or around live circuits, be sure to wear the right PPE to protect against electric shock and arc flash. Never wear clothing made from synthetic materials, such as acetate, nylon, polyester, or rayon - alone or combined with cotton. Such clothing is dangerous because it can burn and melt into your skin.
The type of PPE worn depends on the type of electric work being done (see table 2).
Once the hazard/risk category has been identified, check requirements for clothing and other PPE when working on or near energized equipment within the flash protection boundary (see tables 3 and 4). These PPE requirements protect against electric shock and incurable arc-flash burns. They do not protect against physical injuries from arc blasts.
The minimum PPE required would be an untreated natural fiber long-sleeve shirt and long pants with safety glasses with side shields (hazard/risk category 0).
For more information, call your local union, CPWR – Center for Construction Research and Training (CPWR) (301-578-8500 or www.cpwr.com), the National Institute for Occupational Safety and Health (1-800-35-NIOSH or www.cdc.gov/niosh), or OSHA (1-800-321-OSHA or www.osha.gov)
Table 1. Approach boundaries to live parts for shock prevention
Source: From a portion of table 2-1.3.4, Approach Boundaries to Live Parts for Shock Protection (NFPA 70E Standard for Electrical Safety Requirements for Employee Workplaces, 2000 edition). Tables are reprinted with permission. Copyright ©2000 National Fire Protection Association, Quincy, MA 02269. This reprinted material is not the complete and official position of the National Fire Protection Association on the referenced subject, which is represented only by the standard in its entirety.
Table 2. Hazard risk category classification (within flash protection boundary)
Table 3. Simplified, two-category, flame-resistant clothing system
FR - flame
resistant.
ATPV - arc thermal performance exposure value of the clothing in calories/cm2.
Source: Based on Table F-1 in appendix F of NFPA 70E, Electrical Safety Requirements for Employee Workplaces, 2000.
Table 4. Flame-resistant protective clothing and equipment
Source:
Based on personal protective equipment requirements of table 3-3.9.2
of NFPA 70E, Electrical Safety Requirements for Employee Workplaces.
Tables are reprinted with permission. Copyright ©2000 National
Fire Protection Association, Quincy, MA 02269. This reprinted
material is not the complete and official position of the National
Fire Protection Association on the referenced subject, which is
represented only by the standard in its entirety.
Figure 1. Hazard / risk analysis flow
Source: Adapted from figure D-1 of NFPA 70E, Electrical Safety Requirements for Employee Workplaces. Tables are reprinted with permission. Copyright ©2000 National Fire Protection Association, Quincy, MA 02269. This reprinted material is not the complete and official position of the National Fire Protection Association on the referenced subject, which is represented only by the standard in its entirety.
* OSHA defines an electrical-qualified person as "one familiar with the construction and operation of the equipment and the hazards involved."
**Portions of text are reprinted with permission from NFPA 70E Electrical Safety Requirements for Employee Workplaces, section 2-1.1.3. Copyright ©2000 National Fire Protection Association, Quincy, MA 02269. This reprinted material is not the complete and official position of the National Fire Protection Association on the referenced subject, which is represented only by the standard in its entirety.
***Portions of text are reprinted with permission from NFPA 70E Electrical Safety Requirements for Employee Workplaces, definitions and Part II, Appendix A: Limits of approach. Copyright ©2000 National Fire Protection Association, Quincy, MA 02269. This reprinted material is not the complete and official position of the National Fire Protection Association on the referenced subject, which is represented only by the standard in its entirety.
- Identify the hazards. Do a job hazard analysis (see fig. 1). Identify steps that could create electric shock or arc-flash hazards.
- Minimize the hazards. De-energize the equipment or insulate or isolate exposed live parts so you cannot contact them. If this is impossible, get proper personal protective equipment (PPE) and tools.
- Anticipate problems. If it can go wrong, it might. Make sure you have the right PPE and tools for the worst-case scenario.
- Get training. Make sure you and everyone working with you is a qualified person with appropriate training for the job.*
To De-Energize or Not to De-Energize
One of the most important decisions in planning an electric task is whether to de-energize. Whenever possible, live parts to which you might be exposed should be put into an electrically safe work condition, unless your employer can demonstrate that de-energizing creates more or worse hazards, or is not practical because of equipment design or operational limitations.You might need to work live to avoid interrupting life-support systems, deactivating emergency alarm systems, or shutting down ventilation equipment for hazardous locations, for instance. And de-energizing would not be practical during testing of live electric circuits or work on circuits that are part of a continuous process that cannot be completely shut down.
De-Energizing
An Electrically Safe Work ConditionThe most important principle of electric safety is, assume electric circuits are energized unless you make sure they are not. Test every circuit and conductor every time you work on them. The National Fire Protection Association lists six steps to ensure conditions for electrically safe work.**
- Identify all sources of power to the equipment.
- Interrupt the load current, then open the disconnecting devices for each power source.
- Where possible, visually verify that blades of disconnecting devices are fully open or that drawout-type circuit breakers are fully withdrawn.
- Apply lockout/tagout devices in accordance with a formal, written policy.
- Test each phase conductor or circuit part with an adequately rated voltage detector to verify that the equipment is de-energized. Check the voltage detector before and after each test to be sure it is working.
- Properly ground all possible sources of induced voltage and stored electric energy (such as, capacitors) before touching. If conductors or circuit parts that are being de-energized could contact other exposed conductors or circuit parts, apply ground-connecting devices rated for the available fault current.
Lockout/tagout program
Your employer should establish a written lockout/tagout program and train employees in the program. The program should cover planning for locating and labeling energy sources, identifying employees at risk, how and by whom the equipment is de-energized, releasing of stored energy, verifying that the circuit is de-energized and can't be restarted, voltage testing, grounding requirements, shift changes, coordination with other jobs in progress, a procedure for keeping track of all involved personnel, applying and removing lockout/tagout devices, return to service, and temporary re-energizing for testing/positioning. Lockout/tagout procedures should be developed for each machine or piece of equipment that will require servicing.
Lockout/tagout application. Each person who could be exposed to electric energy must be involved in the lockout/tagout process.
- After de-energizing, each employee at risk should apply an individual lockout/tagout device to each source of electric energy. Pushbuttons or selector switches cannot be used as the only way to de-energize.
- A lockout device is a key or combination lock with a tag that can be attached to a disconnecting device to prevent the re-energizing of the equipment being worked on without removal of the lock. The lockout device should have a way of identifying whose lock it is. Individual lockout devices with your name and picture on them are preferred. You must be the only person who has the key or combination for a lockout device you install, and you should be the only person to remove the lock after all work has been completed.
- A tagout device is a tag and a way to attach it that can withstand at least 50 pounds of force. Tagout devices should be used alone only when it is not possible to install a lockout device.
- The tag used in conjunction with a lockout or tagout device must have a label prohibiting unauthorized operation of the disconnecting means or unauthorized removal of the device.
- Before beginning work, you must verify through testing that all energy sources have been de-energized.
- Electric lockout/tagout procedures should be coordinated with all other site procedures for controlling exposure to electric energy and other types of energy sources.
Complex lockout/tagout procedures. Special procedures are needed when there is more than one energy source, crew, craft, location, employer, way to disconnect, or lockout/tagout procedure - or work that lasts beyond one shift. In any of these cases, one qualified person should be in charge of the lockout/tagout procedure with full responsibility for ensuring all energy sources are under lockout/tagout and to account for all people on the job. There should be a written plan addressing the specific details and naming the person in charge.
Removal of lockout/tagout devices. Lockout and tagout devices should be removed only by the person installing them. If work is not completed when the shift changes, workers arriving on shift should apply their locks before departing workers remove their locks.
Return to service. Once work is completed and lockout/tagout devices removed, tests and visual inspection must confirm that all tools, mechanical restraints, electric jumpers, shorts, and grounds have been removed. Only then is it safe to re-energize and return to service. Employees responsible for operating the equipment and needed to safely re-energize it should be out of the danger zone before equipment is re-energized.
Temporary release. If the job requiring lockout/tagout is interrupted for testing or positioning equipment, follow the same steps as in return to service (above).
Working On or Near Live Circuits
Working on live circuits means actually touching energized parts. Working near live circuits means working close enough to energized parts to pose a risk even though you make be working on de-energized parts. Common tasks where you need to work on or near live circuits include:- Taking voltage measurements
- Opening and closing disconnects and breakers
- Racking breakers on and off the bus
- Removing panels and dead fronts
- Opening electric equipment doors for inspection.
Live-work permit system
A live work permit should, at a minimum, contain this information:
- A description of the circuit and equipment to be worked on and location
- The date and time covered by the permit
- Why live work will be done
- Results of shock hazard analysis and determination of shock protection boundaries
- Results of flash hazard analysis and determination of flash protection boundary
- PPE to be worn and description of safe work practices to be used
- Who will do the work and how unqualified persons will be kept away
- Evidence of completion of job briefing, including description of job-specific hazards.
The National Fire Protection Association defines three approach distances for shock hazards and one for arc flash.*** Electric shock (see table 1).
- The limited approach boundary is the closest distance an unqualified person can approach, unless accompanied by a qualified person.
- The restricted approach boundary is the closest
distance to exposed live parts a qualified person can approach
without proper PPE and tools. Inside this boundary, accidental
movement can put a part of your body or conductive tools in
contact with live parts or inside the prohibited approach
boundary. To cross the restricted approach boundary, the qualified
person must:
- (a) Have a documented plan that is approved by the manager
responsible for the safety plan.
(b) Use PPE suitable for working near exposed live parts and rated for the voltage and energy level involved.
(c) Be certain that no part of the body enters the prohibited space.
(d) Minimize the risk from unintended movement, by keeping as much of the body as possible out of the restricted space; body parts in the restricted space should be protected.
- (a) Have specified training to work on exposed live parts.
(b) Have a documented plan with proper written work procedures and justifying the need to work that close.
(c) Do a written risk analysis.
(d) Have (b) and (c) approved by the manager responsible for the safety plan.
(e) Use PPE appropriate for working near exposed live parts and rated for the voltage and energy level involved.
Remember, when you have de-energized the parts you are going to work on, but are still inside the flash protection boundary for nearby live exposed parts: If the parts cannot be de-energized, you must use barriers such as insulated blankets to protect against accidental contact or you must wear proper PPE.
Proper Personal Protective Equipment
When working on or around live circuits, be sure to wear the right PPE to protect against electric shock and arc flash. Never wear clothing made from synthetic materials, such as acetate, nylon, polyester, or rayon - alone or combined with cotton. Such clothing is dangerous because it can burn and melt into your skin.
The type of PPE worn depends on the type of electric work being done (see table 2).
Once the hazard/risk category has been identified, check requirements for clothing and other PPE when working on or near energized equipment within the flash protection boundary (see tables 3 and 4). These PPE requirements protect against electric shock and incurable arc-flash burns. They do not protect against physical injuries from arc blasts.
The minimum PPE required would be an untreated natural fiber long-sleeve shirt and long pants with safety glasses with side shields (hazard/risk category 0).
For more information, call your local union, CPWR – Center for Construction Research and Training (CPWR) (301-578-8500 or www.cpwr.com), the National Institute for Occupational Safety and Health (1-800-35-NIOSH or www.cdc.gov/niosh), or OSHA (1-800-321-OSHA or www.osha.gov)
Table 1. Approach boundaries to live parts for shock prevention
| Limited approach boundary | ||||
| Nominal system voltage range, phase to phase | Exposed movable conductor | Exposed fixed- circuit part | Restricted approach boundary (allowing for accidental movement) | Prohibited approach boundary |
| 0 to 50 volts | Not specified | Not specified | Not specified | Not specified |
| 51 to 300 volts | 10 ft. 0 in. | 3 ft. 6 in. | Avoid contact | Avoid contact |
| 301 to 750 volts | 10 ft. 0 in. | 3 ft. 6 in. | 1 ft. 0 in. | 0 ft. 1 in. |
| 751 to 15,000 volts | 10 ft. 0 in. | 5 ft. 0 in. | 2 ft. 2 in. | 0 ft. 7 in. |
Source: From a portion of table 2-1.3.4, Approach Boundaries to Live Parts for Shock Protection (NFPA 70E Standard for Electrical Safety Requirements for Employee Workplaces, 2000 edition). Tables are reprinted with permission. Copyright ©2000 National Fire Protection Association, Quincy, MA 02269. This reprinted material is not the complete and official position of the National Fire Protection Association on the referenced subject, which is represented only by the standard in its entirety.
Table 2. Hazard risk category classification (within flash protection boundary)
| For low-voltage tasks (600 volts and below), this table applies only when there is an available short-circuit capacity of 25 kA or less, and when the fault clearing time is 0.03 seconds (2 cycles) or less. For 600-volt-class motor control centers, a short-circuit current capacity of 65 kA or less and fault-clearing time of 0.33 seconds (20 cycles) is allowed. For 600-volt-class switchgear, you need a short-circuit current capacity of 65 kA or less and fault-clearing time of 1 second (60 cycles). For tasks not covered in this table and tasks involving equipment with larger short-circuit current capacities or longer fault-clearing times, a qualified person must conduct a flash hazard analysis (see section 2-1.3.3, Part II, NFPA 70E). |
| Hazard/risk
category |
Voltage-rated
Gloves Tools |
|||
| Opening Doors and Covers | ||||
| Opening hinged covers (to expose bare, energized parts) | ||||
| 240 volts or less |
0
|
N
|
N
|
|
| 600-volt-class motor control centers |
1
|
N
|
N
|
|
| 600-volt-class lighting or small power transformers |
1
|
N
|
N
|
|
| 600-volt-class switchgear (with power circuit breakers or fused switches) |
2
|
N
|
N
|
|
| NEMA E2 (fused contactor) motor starters, 2.3 kV through 7.2 kV |
3
|
N
|
N
|
|
| 1 kV and over (metal clad switchgear) |
3
|
N
|
N
|
|
| 1 kV and above metal clad load interrupter switches, fused or unfused |
3
|
N
|
N
|
|
| Removing bolted covers (to expose bare, energized parts) | ||||
| 240 volts or less |
1
|
N
|
N
|
|
| 600-volt-class motor control centers or transformers |
2*
|
N
|
N
|
|
| 600-volt-class lighting or small power transformers |
2*
|
N
|
N
|
|
| 600-volt-class switchgear (with power circuit breakers or fused switches) |
3
|
N
|
N
|
|
| NEMA E2 (fused contactor) motor starters, 2.3 kV through 7.2 kV |
4
|
N
|
N
|
|
| 1 kV and above (metal clad switchgear) |
4
|
N
|
N
|
|
| 1 kV and above metal clad load interrupter switches, fused or unfused |
4
|
N
|
N
|
|
| Opening transformer compartments for metal clad switchgear 1 kV and above |
4
|
N
|
N
|
|
| Installing, Removing or Operating Circuit Breakers (CBs), Fused Switches, Motor Starters or Fused Contactors | ||||
| Installing or removing circuit breakers or fused switches, 240 volts or less |
1
|
Y
|
Y
|
|
|
Inserting
or removing (racking) CBs from cubicles, doors closed
|
||||
| 600-volt-class switchgear (with power circuit breakers or fused switches) |
2
|
N
|
N
|
|
| NEMA E2 (fused contactor) motor starters, 2.3 kV through 7.2 kV |
2
|
N
|
N
|
|
| 1 kV and above metal clad switchgear |
2
|
N
|
N
|
|
| Inserting or removing (racking) CBs or starters from cubicles, doors open | ||||
| 600-volt-class switchgear (with power circuit breakers or fused switches) |
3
|
N
|
N
|
|
| NEMA E2 (fused contactor) Motor Starters, 2.3 kV through 7.2 kV |
3
|
N
|
N
|
|
| 1 kV and above metal clad switchgear |
4
|
N
|
N
|
|
| Operating circuit breaker (CB), fused switch, motor starter or fused contactor, covers on/doors closed | ||||
| 240 volts or less |
0
|
N
|
N
|
|
| >240-<600 volt panelboards> |
0
|
N
|
N
|
|
| 600 volt class motor control centers |
0
|
N
|
N
|
|
| 600 volt class switchgear (with power circuit breakers or fused switches) |
0
|
N
|
N
|
|
| NEMA E2 (fused contactor) motor starters, 2.3 kV through 7.2 kV |
0
|
N
|
N
|
|
| 1 kV and above (metal clad switchgear) |
2
|
N
|
N
|
|
| 1 kV and above metal clad load interrupter switches, fused or unfused |
2
|
N
|
N
|
|
| Operating circuit breaker, fused switch, motor starter or fused contactor, covers off/doors open | ||||
| 240 volts or less |
0
|
N
|
N
|
|
| >240-<600 volt panelboards> |
1
|
N
|
N
|
|
| 600 volt class motor control centers |
1
|
N
|
N
|
|
| 600 volt class switchgear (with power circuit breakers or fused switches) |
1
|
N
|
N
|
|
| NEMA E2 (fused contactor) motor starters, 2.3 kV through 7.2 kV |
2*
|
N
|
N
|
|
| 1 kV and above (metal clad switchgear) |
4
|
N
|
N
|
|
| Working on Energized Parts | ||||
| Working on energized parts, voltage testing, applying safety grounds | ||||
| 240 volts or less |
1
|
Y
|
Y
|
|
| >240-<600 volt panelboards> |
2*
|
Y
|
Y
|
|
| 600-volt-class motor control centers |
2*
|
Y
|
Y
|
|
| 600-volt-class switchgear (with power circuit breakers or fused switches) |
2*
|
Y
|
Y
|
|
| 600-volt-class lighting or small power transformers |
2*
|
Y
|
Y
|
|
| 600-volt-class revenue meters |
2*
|
Y
|
Y
|
|
| NEMA E2 (fused contactor) motor starters, 2.3 kV through 7.2 kV |
3
|
Y
|
Y
|
|
| 1 kV and above metal clad switchgear |
4
|
Y
|
Y
|
|
| 1 kV and above metal clad load interrupter switches, fused or unfused |
4
|
Y
|
Y
|
|
| Working on control circuits with exposed energized parts, 120 volts or below | ||||
| 600-volt-class motor control centers |
0
|
Y
|
Y
|
|
| 600-volt-class switchgear (with power circuit breakers or fused switches |
0
|
Y
|
Y
|
|
| NEMA E2 (fused contactor) motor starters, 2.3 kV through 7.2 kV |
0
|
Y
|
Y
|
|
| 1 kV and above metal clad switchgear |
2
|
Y
|
Y
|
|
| Working on control circuits with exposed energized parts, over 120 volts | ||||
| 600-volt-class Motor Control Centers |
2*
|
Y
|
Y
|
|
| 600-volt-class switchgear (with power circuit breakers or fused switches) |
2*
|
Y
|
Y
|
|
| NEMA E2 (fused contactor) motor starters, 2.3 kV through 7.2 kV |
3
|
Y
|
Y
|
|
| 1 kV and above metal clad switchgear |
4
|
Y
|
Y
|
|
| Other Tasks | ||||
| Reading panel meters while operating meter switches |
0
|
N
|
N
|
|
| Metal clad load interrupter switches, fused or unfused, 1 kV and above | ||||
| Outdoor disconnect switch operation (hookstick operated) |
3
|
Y
|
Y
|
|
| Outdoor disconnect switch operation (gang-operated, from grade) |
2
|
N
|
N
|
|
| Insulated cable examination, in open area |
2
|
Y
|
N
|
|
| Insulated cable examination, in manhole or other confined space |
4
|
Y
|
N
|
|
| Removing/installing other equipment | ||||
| Starter "buckets" for 600-volt-class motor control centers |
3
|
Y
|
N
|
|
| 600-volt-class revenue meters |
2*
|
Y
|
N
|
|
| Covers or cable troughs for 600-volt-class revenue meters |
1
|
N
|
N
|
|
| 2* = A double-layer switching hood and hearing protection are required, in addition to the other hazard/risk category 2 requirements of table 3-3.9.2 of Part II of NFPA 70E. See tables 3 and 4. | ||||
| kV = kilovolt | ||||
| Note: Applying safety grounds after voltage testing does not require voltage-rated tools. Voltage-rated gloves or tools are rated and tested for the maximum line-to-line voltage on which work will be done. The hazard/risk category may be reduced by one number for low-voltage equipment listed here where the short-circuit current available is less than 15 kA (less than 25 kA for 600-volt-class switchgear). | ||||
| Source: Adapted from table 3-3.9.1, Hazard Risk Category Classifications (NFPA 70E Standard for Electrical Safety Requirements for Employee Workplaces, 2000 edition). Tables are reprinted with permission. Copyright ©2000 National Fire Protection Association, Quincy, MA 02269. This reprinted material is not the complete and official position of the National Fire Protection Association on the referenced subject, which is represented only by the standard in its entirety. | ||||
Table 3. Simplified, two-category, flame-resistant clothing system
| Applicable tasks | Clothing requirement |
| All
hazard/risk category 1 and 2 tasks listed in table 2
On systems operating at less than 1000 volts, these tasks include work on all equipment except
|
Everyday
work clothing Flame-resistant long-sleeve shirt (minimum ATPV of 5) worn over an untreated cotton T-shirt with FR pants (minimum ATPV of 8) Or FR coveralls (minimum ATPV of 5) worn over an untreated cotton T-shirt (or an untreated natural-fiber long-sleeve shirt) with untreated natural-fiber pants. |
| All
hazard/risk category 3 and 4 tasks listed in table 2
On systems operating at 1000 volts or more, these tasks include work on energized parts of all equipment. On systems of less than 1000 volts, tasks include insertion or removal of low-voltage motor-start motor control center "buckets," insertion or removal of power circuit breakers with the switchgear enclosure doors open, and removal of bolted covers from switchgear. |
Electric
"switching" clothing Double-layer FR flash jacket and FR bib overalls worn over either FR coveralls (minimum ATPV of 5) or FR long-sleeve shirt and FR pants (minimum ATPV of 5) worn over untreated natural-fiber long-sleeve shirt and pants worn over an untreated cotton T-shirt Or Insulated FR coveralls (minimum ATPV of 25, independent of other layers) worn over untreated natural-fiber long-sleeve shirt with untreated cotton blue jeans ("regular weight," minimum 12 oz./sq. yd. fabric weight), worn over an untreated cotton T-shirt. |
ATPV - arc thermal performance exposure value of the clothing in calories/cm2.
Source: Based on Table F-1 in appendix F of NFPA 70E, Electrical Safety Requirements for Employee Workplaces, 2000.
Table 4. Flame-resistant protective clothing and equipment
| Flame-resistant protective clothing and equipment | Protective systems for hazard/risk category (4 = most hazardous) | |||
| Hazard/risk
category number Flash suit jacket (2-layer) Flash suit pants (2-layer) Head protection Hardhat Flame-resistant hardhat liner Eye protection (safety glasses + side shields or safety goggles) Face protection (double-layer switching hood) Hearing protection (ear canal inserts) Leather gloves or voltage-rated gloves with leather protectors Leather work shoes |
1
X X
As needed As needed |
2
X X 2* tasks 2*tasks X |
3 X X X X X X X |
4 X X X X X X X X X X |
Figure 1. Hazard / risk analysis flow
Source: Adapted from figure D-1 of NFPA 70E, Electrical Safety Requirements for Employee Workplaces. Tables are reprinted with permission. Copyright ©2000 National Fire Protection Association, Quincy, MA 02269. This reprinted material is not the complete and official position of the National Fire Protection Association on the referenced subject, which is represented only by the standard in its entirety.
* OSHA defines an electrical-qualified person as "one familiar with the construction and operation of the equipment and the hazards involved."
**Portions of text are reprinted with permission from NFPA 70E Electrical Safety Requirements for Employee Workplaces, section 2-1.1.3. Copyright ©2000 National Fire Protection Association, Quincy, MA 02269. This reprinted material is not the complete and official position of the National Fire Protection Association on the referenced subject, which is represented only by the standard in its entirety.
***Portions of text are reprinted with permission from NFPA 70E Electrical Safety Requirements for Employee Workplaces, definitions and Part II, Appendix A: Limits of approach. Copyright ©2000 National Fire Protection Association, Quincy, MA 02269. This reprinted material is not the complete and official position of the National Fire Protection Association on the referenced subject, which is represented only by the standard in its entirety.
