1. What is arc flash
2. OSHA, NFPA 70E
3. Codes and standards
4. Protective clothing and equipment
5. Prevention
An arc flash (or arc blast) is a type of electrical explosion that results from a low impedance connection to ground or another voltage phase in an electrical system
Even without electrocution, death or dismemberment may occur through an intense arc blast, up to 35,000 F deg, and force up to 2100 psi from the intense heat rapidly expanding the air, copper & particles creating a shockwave blast. Droplets of molten metal and shrapnel can penetrate the body.
2. Five Main Topics
1. What is arc flash
2. OSHA, NFPA 70E
3. Codes and standards
4. Protective clothing and equipment
5. Prevention
3. Arc Flash Basics
• An arc flash (or arc blast) is a type of electrical explosion that results from a low
impedance connection to ground or another voltage phase in an electrical system
• Even without electrocution, death or dismemberment may occur through an intense
arc blast, up to 35,000 F deg, and force up to 2100 psi from the intense heat rapidly
expanding the air, copper & particles creating a shockwave blast. Droplets of molten
metal and shrapnel can penetrate the body.
8. Electrical Workplace Safety Standards
The OSHA / NFPA 70E mix
OSHA sets the functional requirements but does not provide procedural detail
(what must be done)
NFPA 70E provides procedural recommendations for how to meet functional
electrical safety goals (how to recommendations)
NFPA 70E procedural provisions are based on OSHA requirements and OSHA
citations reference NFPA 70E recommendations
Thus, although OSHA is law and NFPA 70E is not, NFPA 70E recommendations are
effectively de facto requirements
14. Arc Flash Hazard Labels
The following arc flash label would suffice in meeting the requirements of
NEC Article 110.16 but may not suffice in meeting NFPA 70E – 2009.
15. Arc Flash Hazard Labels
Equipment Labeling. Equipment shall be field marked with a label containing
the available incident energy or required level of PPE. Below is an example of
NFPA70E recommended label warnings.
27’.8”
20. NEC®
Definition
NFPA 70 National Electrical Code®
, 2011 Edition
Qualified Person. One who has skills and knowledge related to the construction
and operation of the electrical equipment and installations and has received
safety training to recognize and avoid the hazards involved.
FPN: Refer to NFPA 70E®-2009, Standard for Electrical Safety in the
Workplace, for electrical safety training requirements.
21. Qualified Person
NFPA 70 E Standard for Electrical Safety in the Workplace,
2009 Edition
Qualified Person. A qualified person shall be:
Trained and knowledgeable of the construction and operation of equipment
or a specific work method
Trained to recognize and avoid the electrical hazards that might be present
with respect to that equipment or work method.
22. Qualified Person
NFPA 70 E Standard for Electrical Safety in the Workplace,
2009 Edition
The employer shall document that each employee has received the
training required. This documentation shall be made when the employee
demonstrates proficiency in the work practices involved and shall be
maintained for the duration of the employee’s employment. The
documentation shall contain each employee’s name and dates of training.
30. Limit the ‘Incident Energy’ level of the
arc flash to 1.2 cal/cm² against the
worker’s chest.
Look for a label that states:
1506 approval (ASTM F1506)
Arc rating of the garment
All materials in the garment
should be FR Rated:
Thread
Buttons
Insulation
Zippers, etc.
FR Rated Clothing
Photo compliments of
Salisbury Electrical Safety L.L.C.
31. Increases level of protection.
May be lighter than a single
heavy garment.
Manufacturer must provide
the new combined arc rating
afforded by layering.
FR Clothing Can Be Layered
Photo compliments of
Salisbury Electrical Safety L.L.C.
32. Tell the supplier that you need
arc flash rated PPE and clothing.
PPE must have some resistance to:
Flame
Ignition
Melting.
obtain PPE from a known and trusted supplier
When Purchasing PPE
Not all FR clothing is tested to ASTM F1506
Photo compliments of
Salisbury Electrical Safety L.L.C.
33. Synthetic Clothing
Synthetic clothing that melts shall not be worn, such as:
Acetate
Nylon
Polyester
Polypropylene
Spandex
34. Arc Flash Rated PPE
ASTM F1506 is the certification for arc flash resistant clothing.
Required minimum clothing:
Non-melting, flammable material,
Fabric weight of at least 4.5 oz/yd.
PPE must also provide
arc flash protection:
Face shield
Gloves, etc.
Photo compliments of
Salisbury Electrical Safety L.L.C.
About 30% of reported electrical hazard injuries involve arc flash
Arc flash is NOT limited to medium and high Voltages
Arc flash events propagate in a few hundredths of a second
Temperatures can reach 35,000 °F (4x the temperature of the sun‘s surface)
Most arc fault incidents are initiated by some form of inadvertent contact
Arc flash energy is typically expressed in cal / cm2
PER NEMA UL 508C
Motor controller, rated in horsepower (kW)
a. 0 - 50 (0 - 37.3) 5 c
b. 51 - 200 (38 - 149) 10 c
c. 201 - 400 (150 - 298) 18 c
d. 401 - 600 (299 - 447) 30 c
e. 601 - 900 (448 - 671) 42 c
f. 901 - 1500 (672 - 1193) 85 c
NFPA 70 E defines Arc Flash Protection Boundary as follows”
“When an arc flash hazard exists, an approach limit at a distance from a prospective arc source within which a person could receive a second degree burn if an electrical arc flash were to occur”
1926.28 Personal protective equipment
The employer is responsible for
requiring the wearing of appropriate
personal protective equipment in all
operations where there is an exposure
to hazardous conditions or where this
part indicates the need for using such
equipment to reduce the hazards to the
employees.
(b) Regulations governing the use, selection,
and maintenance of personal
protective and lifesaving equipment
are described under subpart E of this
part.
1926.417 Lockout and tagging of circuits.
(a) Controls. Controls that are to be
deactivated during the course of work
on energized or deenergized equipment
or circuits shall be tagged.
(b) Equipment and circuits. Equipment
or circuits that are deenergized shall
be rendered inoperative and shall have
tags attached at all points where such
equipment or circuits can be energized.
(c) Tags. Tags shall be placed to identify
plainly the equipment or circuits
being worked on.
Subpart E—Personal Protective and Life
Saving Equipment
1926.95 Criteria for personal protective
equipment.
1926.96 Occupational foot protection.
1926.97–1926.98 [Reserved]
1926.100 Head protection.
1926.101 Hearing protection.
1926.102 Eye and face protection.
1926.103 Respiratory protection.
1926.104 Safety belts, lifelines, and lanyards.
1926.105 Safety nets.
1926.106 Working over or near water.
1926.107 Definitions applicable to this subpart
Without arc flash hazard analysis, which at a minimum requires the determination of the potential short circuit current and knowledge of the overcurrent protective device, short of testing, it is impossible to determine the Incident Energy.
Therefore, without arc flash hazard analysis, the only information that can be included on label is the Required Level of PPE.
NFPA 70 E does not define what is meant by the “Required Level of PPE” and it only defines methods that should be used for the selection of protective clothing and other personnel protective equipment for work performed within the Arc Flash Protection Boundary.
Even if no Arc Flash Hazard Category is defined, Safety glasses or goggles and hearing protection should be required for any electrical work near exposed energized parts except for circuits originating from Class II power sources as defined by Section 725 of the NEC
Arc Flash labels are required on equipment “such as”
panelboards, switchboards, motor control centers,
industrial control panels and meter sockets,
Arc Flash labels are required on motor starters,
variable frequency drives, plug-in bus duct, equipment
control panels and building management panels if they
contain equipment that is 50 volts or higher and are
“likely to require examination, adjustment, servicing or
maintenance while energized”.
Without arc flash hazard analysis, which at a minimum requires the determination of the potential short circuit current and knowledge of the overcurrent protective device, short of testing, it is impossible to determine the Incident Energy.
Therefore, without arc flash hazard analysis, the only information that can be included on label is the Required Level of PPE.
NFPA 70 E does not define what is meant by the “Required Level of PPE” and it only defines methods that should be used for the selection of protective clothing and other personnel protective equipment for work performed within the Arc Flash Protection Boundary.
Even if no Arc Flash Hazard Category is defined, Safety glasses or goggles and hearing protection should be required for any electrical work near exposed energized parts except for circuits originating from Class II power sources as defined by Section 725 of the NEC
Arc Flash labels are required on equipment “such as” panelboards, switchboards, motor control centers,
industrial control panels and meter sockets,
Arc Flash labels are required on motor starters, variable frequency drives, plug-in bus duct, equipment control panels and building management panels if they contain equipment that is 50 volts or higher and are “likely to require examination, adjustment, servicing or maintenance while energized”.
Qualified persons shall be familiar with the proper use of:
The special precautionary techniques,
Personal Protective Equipment, including Arc-flash, Insulating and Shielding materials, Insulated tools and test equipment.
Employees shall be trained to select an appropriate voltage detector and shall demonstrate how to use a device to verify the absence of voltage, including interpreting indications provided by the device. The training shall include information that enables the employee to understand all limitations of each specific voltage detector that may be used.
A person can be considered qualified with respect to certain equipment and methods but still be unqualified for others.
Qualified persons permitted to work within the Limited Approach Boundary of exposed energized electrical conductors and circuit parts operating at 50 volts or more shall, at a minimum, be additionally trained in all of the following:
The skills and techniques necessary to distinguish exposed energized electrical conductors and circuit parts from other parts of electrical equipment.
(2) The skills and techniques necessary to determine the nominal voltage of exposed energized electrical conductors and circuit parts
(3) The approach distances specified in Table 130.2(C) and the corresponding voltages to which the qualified person will be exposed.
(4) The decision-making process necessary to determine the degree and extent of the hazard and the personal protective equipment and job planning necessary to perform the task safely
An employee who is undergoing on-the-job training and who, in the course of such training, has demonstrated an ability to perform duties safely at his or her level of training and who is under the direct supervision of a qualified person shall be considered to be a qualified person for the performance of those duties.
Tasks that are performed less often than once per year shall require retraining before the performance of the work practices involved.
OSHA commonly uses the “General Duty Clause”,
which is paraphrased below or as an alternate
uses NFPA 70E or the NEC for citations related to arc
flash incidents.
General Duty Clause:
Section 5(a)(1) of the Occupational Safety and Health Act requires an employer to furnish to its employees “employment and a place of employment which are free from recognized hazards that are causing or are likely to cause death or serious physical harm to his employees”
Verify – Test/Measure – Re-Verify
Typical PPE Requirements
This information is based on the 2009 edition of Workplace Electrical Safety, Table 5 Hazard/risk categorization of protective clothing and PPE. More information on PPE selection is available in the table and the accompanying notes.
In most applications clothing and PPE must be either be FR rated or arc-flash rated. Note the arc rating associated with each hazard/risk category. Do not wear materials such as nylon and polyester that can melt. Non-FR-rated undergarments (and PPE) may catch fire even when arc-rated clothing worn overtop survives an arc flash.
All categories 0 – 4 require:
either safety glasses or safety goggles,
ear canal inserts; and,
long sleeve shirt and pants that are non-melting, arc-rated to ASTM F-1506 or untreated natural fibre.
Category 1 requires clothing to be arc-rated to ASTM F-1506. Hard hat and arc rated face shield are also required as additional head and eye protection. Face shields must have wrap-around guarding to protect the forehead, ears, and neck.
Some category 2 tasks require the use of a flash suit hood in place of an arc-rated face shield; however, there is also an option to substitute the flash suit hood for a combination of a face shield with a balaclava (sock hood). Both the face shield and balaclava must be arc rated.
Categories 3 and 4 will require the use of a flash suit hood.
IEEE 1584 – 2002 states the following relative to the use of PPE:
“Where used, PPE for the arc-flash hazard is the last line of defense. The protection is not intended to prevent all injuries but to mitigate the impact of an arc flash upon the individual, should one occur. In many cases, the use of PPE has saved lives or prevented injury. The calculations in this guide will lead to selection of a level of PPE that is a balance between the calculated estimated incident energy exposure and the work activity being performed while meeting the following concerns
This information is based on the 2009 edition, Workplace Electrical Safety, Table 6 Protective Clothing Characteristics.
Hazard/risk category 0: Non-melting flammable material with fabric weight of at least 4.5 oz/yd2.
Hazard/risk category 1: Arc-rated FR shirt + FR pants or FR coveralls.
Hazard risk category 2: Arc-rated FR shirt + FR pants or FR coveralls.
Hazard/risk category 3: Arc-rated FR shirt + FR pants or FR coveralls, and Arc-rated flash suit, selected so the layered system meets the required minimum rating.
Hazard/risk category 4: Arc-rated FR shirt + FR pants or FR coveralls, and Arc-rated flash suit, selected so the layered system meets the required minimum rating.
Do not wear materials such as nylon and polyester that can melt. Non-FR-rated undergarments (and PPE) may catch fire even when arc-rated clothing worn overtop easily survives an arc flash.
Important Note:
FR clothing will not also be arc-rated unless it meets ASTM F1506.
See Topic 4 – Protective Clothing and Equipment.
An arc flash analysis will identify the level of incident energy available and thereby the level of protection the worker requires.
ASTM F1506* is a standard that was developed to give minimum performance specifications for protective clothing.
Uses a hazard risk category system to identify the incident energy a worker would be exposed while performing a task.
The category level (0 to 4) is used to identify a level of protection for the worker, which simplifies PPE choice.
*ASTM F1506 = Standard Performance Specification for Textile Materials for Wearing Apparel for Use by Electrical Workers Exposed to Momentary Arc and Related Thermal Hazards.
Arc rated clothing may be layered to increase the level of protection.
For example, wearing FR coveralls over FR shirt and FR pants.
Layered clothing is more versatile and may result in garments that are lighter than if a single heavy garment were used.
The manufacturer must provide information on the increased protection afforded by layering their clothing.
The new arc flash rating of the layering must however be verified by the manufacturer through testing.
Instead, ASTM F1506 is the certification for arc flash resistant clothing.
Table 5 in CSA Z462 Protective Clothing and Personal Protective Equipment (PPE) mentions protective equipment that must be FR rated, however it also identifies a number of the items have no FR requirement stated.
Purchasers should obtain PPE from a known and trusted supplier.
Non-rated clothing, and other PPE that can melt or catch fire, exposes the worker to serious burn injury.
Even when arc rated clothing easily survives an arc flash, non FR-rated clothing, including undergarments and other PPE that can melt or catch fire, have caused workers to be severely injured when it either burned or melted on the workers skin. The result is extremely painful and lengthy hospitalization and rehabilitation, and permanent changes to their quality of life.
Arc Flash PPE
ASTM F1506 is the certification for arc flash resistant clothing.
Face shields commonly used for grinding and cutting are not arc flash rated and may melt. Arc flash resistant face shields must meet ASTM F2178 specifications to comply with NFPA 70E (and CSA Z462 - 08) for arc flash protection.
Hard hats, safety glasses, leather work boots, and leather gloves, for example, may either be inherently flame resistant or designed to another standard that provides some protection against flammability, ignition, and melting.
The material used in manufacturing makes a difference. Generally, ear canal inserts made of PVC are more flame resistant than inserts made from polyurethane.
Drive designs with protective covers or shields provide increased safety.