California Code of Regulations › Title 8 - Industrial Relations › Division 1 - Department of Industrial Relations › Chapter 4 - Division of Industrial Safety › Subchapter 5 - Electrical Safety Orders › Group 2 - High-Voltage Electrical Safety Orders › Article 36 - Work Procedures and Operating Procedures › Appendix D - Protection from Flames and Electric Arcs

Current through Register 2024 Notice Reg. No. 28, July 12, 2024
I. Introduction
Section
						  2940.11 addresses protecting
						  employees from flames and electric arcs. This ssection requires employers to:
						  (1) Assess the workplace for flame and electric-arc hazards; (2) estimate the
						  available heat energy from electric arcs to which employees would be exposed;
						  (3) ensure that employees wear clothing that will not melt, or ignite and
						  continue to burn, when exposed to flames or the estimated heat energy; and (4)
						  ensure that employees wear flame-resistant clothing [FN1] and protective
						  clothing and other protective equipment that has an arc rating greater than or
						  equal to the available heat energy under certain conditions. This appendix
						  contains information to help employers estimate available heat energy, select
						  protective clothing and other protective equipment with an arc rating suitable
						  for the available heat energy, and ensure that employees do not wear flammable
						  clothing that could lead to burn injury.
II. Assessing the Workplace for Flame and
						  Electric-Arc Hazards
Section
						  2940.11(a)(1)
						  requires the employer to assess the workplace to identify employees exposed to
						  hazards from flames or from electric arcs. This provision ensures that the
						  employer evaluates employee exposure to flames and electric arcs so that
						  employees who face such exposures receive the required protection. The employer
						  shall conduct an assessment for each employee who performs work on or near
						  exposed, energized parts of electric circuits.
A.
Assessment Guidelines
Sources electric arcs.
Consider
						  possible sources of electric arcs, including:
* Energized circuit parts not guarded or
						  insulated,
* Switching devices that produce electric arcs in
						  normal operation,
* Sliding parts that could fault during operation (for
						  example, rack-mounted circuit breakers), and
* Energized electric equipment that could fail (for
						  example, electric equipment with damaged insulation or with evidence of arcing
						  or overheating)
Exposure to flames.
Identify employees
						  exposed to hazards from flames. Factors to consider include:
* The proximity of employees to open flames, and
* For flammable material in the work area, whether
						  there is a reasonable likelihood that an electric arc or an open flame can
						  ignite the material.
Probability that an electric arc will
						  occur.
Identify employees exposed to electric-arc hazards. The
						  Division of Occupational Safety and Health will consider an employee exposed to
						  electric-arc hazards if there is a reasonable likelihood that an electric arc
						  will occur in the employee's work area, in other words, if the probability of
						  such an event is higher than it is for the normal operation of enclosed
						  equipment. Factors to consider include:
* For energized circuit parts not guarded or insulated,
						  whether conductive objects can come too close to or fall onto the energized
						  parts,
* For exposed, energized circuit parts, whether the
						  employee is closer to the part than the minimum approach distance established
						  by the employer (as permitted by Section
						  2940.2)
* Whether the operation of electric equipment with
						  sliding parts that could fault during operation is part of the normal operation
						  of the equipment or occurs during servicing or maintenance, and
* For energized electric equipment, whether there is
						  evidence of impending failure, such as evidence of arcing or
						  overheating.
B.
Examples
Table 1 provides task-based examples of exposure
						  assessments.
TABLE 1-EXAMPLE
									 ASSESSMENTS FOR VARIOUS TASKS
Task
Is employee
									 exposed to flame or electric arc hazard?
The employer properly installs
								  and
maintains enclosed equipment,
								  and
No.
Normal operation
there is no evidence of
								  impending
of enclosed
failure.
equipment, such
There is evidence of
								  arcing or
Yes.
as closing or
overheating
opening a switch.
Parts of the equipment
								  are loose or
sticking, or the equipment
								  otherwise
Yes.
exhibits signs of lack of
								  maintenance.
Servicing electric equipment, such as
								  racking in a circuit breaker or replacing a switch
Yes.
The employee is not holding
								  conduc-
tive objects and remains outside
								  the
No.
minimum approach distance
established by the employer.
The employee is holding a
								  conductive
Inspection of
object, such as a
								  flashlight, that could
electric equip-
fall or otherwise contact
								  energized
Yes.
ment with ex-
parts (irrespective of
								  whether the
posed energized
employee maintains the
								  minimum
parts.
approach distance).
The employee is closer than the
								  mini-
mum approach distance established
								  by
the employer (for example,
								  when
Yes.
wearing rubber insulating gloves
								  or
rubber insulating gloves and
								  sleeves).
Using open flames, for example, in
								  wiping cable splice sleeves.
Yes.
III. Protection Against Burn Injury
A.
Estimating Available Heat
						  Energy
Calculation methods. Subsection (a)(2) of Section
						  2940.11 provides that, for each
						  employee exposed to an electric-arc hazard, the employer shall make a
						  reasonable estimate of the heat energy to which the employee would be exposed
						  if an arc occurs. Table 2 lists various methods of calculating values of
						  available heat energy from an electric circuit. The Division of Occupational
						  Safety and Health does not endorse any of these specific methods. Each method
						  requires the input of various parameters, such as fault current, the expected
						  length of the electric arc, the distance from the arc to the employee, and the
						  clearing time for the fault (that is, the time the circuit protective devices
						  take to open the circuit and clear the fault). The employer can precisely
						  determine some of these parameters, such as the fault current and the clearing
						  time, for a given system. The employer will need to estimate other parameters,
						  such as the length of the arc and the distance between the arc and the
						  employee, because such parameters vary widely.
TABLE 2 -- METHODS OF CALCULATING INCIDENT HEAT
						  ENERGY FROM AN ELECTRIC ARC
1. Standard for Electrical Safety Requirements for
						  Employee Workplaces, NFPA 70E-2012, Annex D, "Sample Calculation of Flash
						  Protection Boundary."
2. Doughty, T.E., Neal, T.E., and Floyd II, H.L.,
						  "Predicting Incident Energy to Better Manage the Electric Arc Hazard on 600 V
						  Power Distribution Systems," Record of Conference Papers IEEE IAS 45th Annual
						  Petroleum and Chemical Industry Conference, September 28-30, 1998.
3. Guide for Performing Arc-Flash Hazard Calculations,
						  IEEE Std 1584-2002, 1584a-2004 (Amendment 1 to IEEE Std 1584-2002), and
						  1584b-2011 (Amendment 2: Changes to Clause 4 of IEEE Std
						  1584-2002).*
4. ARCPRO, a commercially available software program
						  developed by Kinectrics, Toronto, ON, CA.
* This appendix refers to IEEE Std 1584-2002 with both
						  amendments as IEEE Std 1584b-2011.
The amount of heat energy calculated by any of the
						  methods is approximately inversely proportional to the square of the distance
						  between the employee and the arc. In other words, if the employee is very close
						  to the arc, the heat energy is very high; but if the employee is just a few
						  more centimeters away, the heat energy drops substantially. Thus, estimating
						  the distance from the arc to the employee is key to protecting
						  employees.
The employer shall select a method of estimating
						  incident heat energy that provides a reasonable estimate of incident heat
						  energy for the exposure involved. Table 3 shows which methods provide
						  reasonable estimates for various exposures.
TABLE 3-SELECTING A
									 REASONABLE INCIDENT-ENERGY CALCULATION
									 METHOD
1
Incident-energy calculation
								  method
600 V and
								  Less
2
601 V to 15
								  kV
2
More than 15 kV
1[phi]
3[phi]a
3[phi]b
1[phi]
3[phi]a
3[phi]b
1[phi]
3[phi]a
3[phi]b
NFPA 70E-2012 Annex D (Lee
								  equation)
Y-C
Y
N
Y-C
Y-C
N
N3
N3
N3
Doughty, Neal, and
								  Floyd
Y-C
Y
Y
N
N
N
N
N
N
IEEE Std
								  1584b-2011
Y
Y
Y
Y
Y
Y
N
N
N
ARCPRO
Y
N
N
Y
N
N
Y
Y4
Y4
Key:
1[phi]: Single-phase arc in open
								  air.
3[phi]a: Three-phase arc in open
								  air.
3[phi]b: Three-phase arc in an
								  enclosure (box).
Y: Acceptable; produces a reasonable
								  estimate of incident heat energy from this type of electric arc.
N: Not acceptable; does not produce
								  a reasonable estimate of incident heat energy from this type of electric
								  arc.
Y-C: Acceptable; produces a
								  reasonable, but conservative, estimate of incident heat energy from this type
								  of electric arc.
NOTES:
1 Although the Division of
						  Occupational Safety and Health will consider these methods reasonable for
						  enforcement purposes when employers use the methods in accordance with this
						  table, employers should be aware that the listed methods do not necessarily
						  result in estimates that will provide full protection from internal faults in
						  transformers and similar equipment or from arcs in underground manholes or
						  vaults.
2 At these voltages, the
						  presumption is that the arc is three-phase unless the employer can demonstrate
						  that only one phase is present or that the spacing of the phases is sufficient
						  to prevent a multiphase arc from occurring.
3 Although the Division of
						  Occupational Safety and Health will consider this method acceptable for
						  purposes of assessing whether incident energy exceeds 2.0
						  cal/cm2, the results at voltages of more than 15
						  kilovolts are extremely conservative and unrealistic.
4 The Division of
						  Occupational Safety and Health will deem the results of this method reasonable
						  when the employer adjusts them using the conversion factors for three-phase
						  arcs in open air or in an enclosure, as indicated in the program's
						  instructions.
Selecting a reasonable distance from the
						  employee to the arc.
In estimating available heat energy, the employer
						  shall make some reasonable assumptions about how far the employee will be from
						  the electric arc. Table 4 lists reasonable distances from the employee to the
						  electric arc. The distances in Table 4 are consistent with national consensus
						  standards, such as the Institute of Electrical and Electronic Engineers'
						  National Electrical Safety Code, ANSI/IEEE C2-2012, and IEEE Guide for
						  Performing Arc-Flash Hazard Calculations, IEEE Std 1584b-2011. The employer is
						  free to use other reasonable distances, but shall consider equipment enclosure
						  size and the working distance to the employee in selecting a distance from the
						  employee to the arc. The Division of Occupational Safety and Health will
						  consider a distance reasonable when the employer bases it on equipment size and
						  working distance.
TABLE 4-SELECTING A
									 REASONABLE DISTANCE FROM THE EMPLOYEE TO THE ELECTRIC ARC
Class of
									 equipment
Single-phase arc
									 mm (inches)
Three-phase arc mm
									 (inches)
Cable
NA*
455
								  (18)
Low voltage MCCs and
								  panelboards
NA
455 (18)
Low-voltage switchgear
NA
610
								  (24)
5-kV switchgear
NA
910 (36)
15-kV switchgear
NA
910 (36)
Single conductors in air (up to 46 kilovolts),
								  work with rubber insulating gloves
380 (15)
NA
Single conductors in air, work
MAD - (2 x
								  kV x 2.54)
NA
with live-line tools and live-line barehand
								  work
(MAD - (2 x kV /10)) [DAGGER]
* NA = not applicable.
[DAGGER] The terms in this equation are:
MAD = The applicable minimum approach distance,
						  and
kV = The system voltage in kilovolts.
Selecting a reasonable arc gap.
For a
						  single-phase arc in air, the electric arc will almost always occur when an
						  energized conductor approaches too close to ground. Thus, an employer can
						  determine the arc gap, or arc length, for these exposures by the dielectric
						  strength of air and the voltage on the line. The dielectric strength of air is
						  approximately 10 kilovolts for every 25.4 millimeters (1 inch). For example, at
						  50 kilovolts, the arc gap would be 50 / 10 x 25.4 (or 50 x 2.54), which equals
						  127 millimeters (5 inches).
For three-phase arcs in open air and in enclosures, the
						  arc gap will generally be dependent on the spacing between parts energized at
						  different electrical potentials. Documents such as IEEE Std 1584b-2011 provide
						  information on these distances. Employers may select a reasonable arc gap from
						  Table 5, or they may select any other reasonable arc gap based on sparkover
						  distance or on the spacing between (1) live parts at different potentials or
						  (2) live parts and grounded parts (for example, bus or conductor spacings in
						  equipment). In any event, the employer shall use an estimate that reasonably
						  resembles the actual exposures faced by the employee.
TABLE 5-SELECTING A
									 REASONABLE ARC GAP
Class of
									 equipment
Single-phase arc
									 mm (inches)
Three-phase arc
									 mm1 (inches)
Cable
NA2
13
								  (0.5)
Low voltage MCCs and
								  panelboards
NA
25 (1.0)
Low-voltage switchgear.
NA
32
								  (1.25)
5-kV switchgear
NA
104 (4.0)
15-kV switchgear
NA
152
								  (6.0)
Single conductors in air, 15 kV and
								  less.
51 (2.0)
Phase conductor spacing.
Single conductor in air, more
Voltage in
								  kV x 2.54
Phase
than 15 kV
(Voltage in kV x 0.1), but no
								  less than 51 mm (2 inches).
conductor spacing.
1 Source: IEEE Std
						  1584b-2011.
2 NA = not
						  applicable.
Making estimates over multiple system areas. The
						  employer need not estimate the heat-energy exposure for every job task
						  performed by each employee. Subsection (a)(2) of Section
						  2940.11 permits the employer to
						  make broad estimates that cover multiple system areas provided that: (1) The
						  employer uses reasonable assumptions about the energy-exposure distribution
						  throughout the system, and (2) the estimates represent the maximum exposure for
						  those areas. For example, the employer can use the maximum fault current and
						  clearing time to cover several system areas at once.
Incident heat energy for single-phase-to-ground
						  exposures.
Table 6 and Table 7 provide incident heat energy levels for
						  open air, phase-to-ground electric-arc exposures typical for overhead systems.
						  [FN2] Table 6 presents estimates of available energy for employees using rubber
						  insulating gloves to perform work on overhead systems operating at 4 to 46
						  kilovolts. The table assumes that the employee will be 380 millimeters (15
						  inches) from the electric arc, which is a reasonable estimate for rubber
						  insulating glove work. Table 6 also assumes that the arc length equals the
						  sparkover distance for the maximum transient overvoltage of each voltage range.
						  [FN3] To use the table, an employer would use the voltage, maximum fault
						  current, and maximum clearing time for a system area and, using the appropriate
						  voltage range and fault-current and clearing time values corresponding to the
						  next higher values listed in the table, select the appropriate heat energy (4,
						  5, 8, or 12 cal/cm2) from the table. For example, an
						  employer might have a 12,470-volt power line supplying a system area. The power
						  line can supply a maximum fault current of 8 kiloamperes with a maximum
						  clearing time of 10 cycles. For rubber glove work, this system falls in the
						  4.0-to-15.0-kilovolt range; the next-higher fault current is 10 kA (the second
						  row in that voltage range); and the clearing time is under 18 cycles (the first
						  column to the right of the fault current column). Thus, the available heat
						  energy for this part of the system will be 4 cal/cm2
						  or less (from the column heading), and the employer could select protection
						  with a 5-cal/cm2 rating to meet Section
						  2940.11(b)(2).
						  Alternatively, an employer could select a base incidentenergy value and ensure
						  that the clearing times for each voltage range and fault current listed in the
						  table do not exceed the corresponding clearing time specified in the table. For
						  example, an employer that provides employees with arc-flash protective
						  equipment rated at 8 cal/cm2 can use the table to
						  determine if any system area exceeds 8 cal/cm2 by
						  checking the clearing time for the highest fault current for each voltage range
						  and ensuring that the clearing times do not exceed the values specified in the
						  8-cal/cm2 column in the table.
Table 7 presents similar estimates for employees using
						  live-line tools to perform work on overhead systems operating at voltages of 4
						  to 800 kilovolts. The table assumes that the arc length will be equal to the
						  sparkover distance [FN4] and that the employee will be a distance from the arc
						  equal to the minimum approach distance minus twice the sparkover
						  distance.
The employer will need to use other methods for
						  estimating available heat energy in situations not addressed by Table 6 or
						  Table 7. The calculation methods listed in Table 2 and the guidance provided in
						  Table 3 will help employers do this. For example, employers can use IEEE Std
						  1584b-2011 to estimate the available heat energy (and to select appropriate
						  protective equipment) for many specific conditions, including lower voltage,
						  phase-to-phase arc, and enclosed arc exposures.
TABLE 6-INCIDENT HEAT
									 ENERGY FOR VARIOUS FAULT CURRENTS, CLEARING TIMES, AND VOLTAGES OF 4.0 TO 46.0
									 kV: RUBBER INSULATING GLOVE EXPOSURES INVOLVING PHASE-TO-GROUND ARCS IN OPEN
									 AIR ONLY * [DAGGER] [DOUBLE DAGGER]
Maximum clearing
									 time (cycles)
Voltage range (kV)
									 **
Fault current
									 (kA)
4
									 cal/cm
2
5
									 cal/cm
2
8
									 cal/cm
2
12
									 cal/cm
2
5
46
58
92
138
4.0 to
								  15.0
10
18
22
36
54
15
10
12
20
30
20
6
8
13
19
5
28
34
55
83
15.1 to
								  25.0
10
11
14
23
34
15
7
8
13
20
20
4
5
9
13
5
21
26
42
62
25.1 to
								  36.0
10
9
11
18
26
15
5
6
10
16
20
4
4
7
11
5
16
20
32
48
36.1 to
								  46.0
10
7
9
14
21
15
4
5
8
13
20
3
4
6
9
NOTES:
* This
								  table is for open-air, phase-to-ground electric-arc exposures. It is not for
								  phase-to-phase arcs or enclosed arcs (arc in a box).
[DAGGER] The table assumes that the
								  employee will be 380 mm (15 in.) from the electric arc. The table also assumes
								  the arc length to be the sparkover distance for the maximum transient
								  overvoltage of each voltage range (see Appendix A), as follows:
4.0 to 15.0 kV 51 mm (2 in.)
15.1 to 25.0 kV 102 mm (4 in.)
25.1 to 36.0 kV 152 mm (6 in.)
36.1 to 46.0 kV 229 mm (9 in.)
[DOUBLE DAGGER] The Department of
								  Labor, Occupational Safety and Health Administration calculated the values in
								  this table using the ARCPRO method listed in Table 2.
** The voltage range is the
								  phase-to-phase system voltage.
TABLE 7-INCIDENT HEAT
									 ENERGY FOR VARIOUS FAULT CURRENTS, CLEARING TIMES, AND VOLTAGES: LIVE-LINE TOOL
									 EXPOSURES INVOLVING PHASE-TO-GROUND ARCS IN OPEN AIR ONLY * [DAGGER] [DOUBLE
									 DAGGER] #
Maximum clearing
									 time (cycles)
Voltage range (kV)
									 **
Fault current
									 (kA)
4
									 cal/cm
2
5
									 cal/cm
2
8
									 cal/cm
2
12
									 cal/cm
2
5
197
246
394
591
4.0 to
								  15.0
10
73
92
147
220
15
39
49
78
117
20
24
31
49
73
5
197
246
394
591
15.1 to
								  25.0
10
75
94
150
225
15
41
51
82
122
20
26
33
52
78
5
138
172
275
413
25.1 to
								  36.0
10
53
66
106
159
15
30
37
59
89
20
19
24
38
58
5
129
161
257
386
36.1 to
								  46.0
10
51
64
102
154
15
29
36
58
87
20
19
24
38
57
20
18
23
36
55
46.1 to
								  72.5
30
10
13
20
30
40
6
8
13
19
50
4
6
9
13
20
10
12
20
30
72.6 to
								  121.0
30
6
7
11
17
40
4
5
7
11
50
3
3
5
8
20
12
15
24
35
121.1 to
								  145.0
30
7
9
15
22
40
5
6
10
15
50
4
5
8
11
20
12
15
24
36
145.1 to
								  169.0
30
7
9
15
22
40
5
7
10
16
50
4
5
8
12
20
13
17
27
40
169.1 to
								  242.0
30
8
10
17
25
40
6
7
12
17
50
4
5
9
13
20
25
32
51
76
242.1 to
								  362.0
30
16
19
31
47
40
11
14
22
33
50
8
10
16
25
20
12
15
25
37
362.1 to
								  420.0
30
8
10
15
23
40
5
7
11
16
50
4
5
8
12
20
23
29
47
70
420.1 to
								  550.0
30
14
18
29
43
40
10
13
20
30
50
8
9
15
23
20
25
31
50
75
550.1 to
								  800.0
30
15
19
31
46
40
11
13
21
32
50
8
10
16
24
NOTES:
* This table is for open-air, phase-to-ground
						  electric-arc exposures. It is not for phase-to-phase arcs or enclosed arcs (arc
						  in a box).
[DAGGER] The table assumes the arc length to be the
						  sparkover distance for the maximum phase-to-ground voltage of each voltage
						  range (see Appendix A). The table also assumes that the employee will be the
						  minimum approach distance minus twice the arc length from the electric
						  arc.
[DOUBLE DAGGER] The Department of Labor, Occupational
						  Safety and Health Administration calculated the values in this table using the
						  ARCPRO method listed in Table 2.
# For voltages of more than 72.6 kV, employers may use
						  this table only when the minimum approach distance established under Section
						  2940.2 (a) is
						  greater than or equal to the following values:
72.6 to 121.0 kV
1.02 m.
121.1 to 145.0 kV
1.16 m.
145.1 to 169.0 kV
1.30 m.
169.1 to 242.0 kV
1.72 m.
242.1 to 362.0 kV
2.76 m.
362.1 to 420.0 kV
2.50 m.
420.1 to 550.0 kV
3.62 m.
550.1 to 800.0 kV
4.83 m.
** The voltage range is the phase-to-phase system
						  voltage.
B.
Selecting Protective Clothing and Other
						  Protective Equipment
Subsection (b) of Section
						  2940.11 requires employers, in
						  certain situations, to select protective clothing and other protective
						  equipment with an arc rating that is greater than or equal to the incident heat
						  energy estimated under Section
						  2940.11(a)(2).
						  Based on laboratory testing required by ASTM F1506-10a, the expectation is that
						  protective clothing with an arc rating equal to the estimated incident heat
						  energy will be capable of preventing second-degree burn injury to an employee
						  exposed to that incident heat energy from an electric arc. Note that actual
						  electric-arc exposures may be more or less severe than the estimated value
						  because of factors such as arc movement, arc length, arcing from reclosing of
						  the system, secondary fires or explosions, and weather conditions.
						  Additionally, for arc rating based on the fabric's arc thermal performance
						  value [FN5] (ATPV), a worker exposed to incident energy at the arc rating has a
						  50-percent chance of just barely receiving a second-degree burn. Therefore, it
						  is possible (although not likely) that an employee will sustain a second-degree
						  (or worse) burn wearing clothing conforming to Section
						  2940.11(b)(2)
						  under certain circumstances. However, reasonable employer estimates and
						  maintaining appropriate minimum approach distances for employees should limit
						  burns to relatively small burns that just barely extend beyond the epidermis
						  (that is, just barely a second degree burn). Consequently, protective clothing
						  and other protective equipment meeting Section
						  2940.11(b)(2) will
						  provide an appropriate degree of protection for an employee exposed to
						  electric-arc hazards.
Subsection (b)(2) of Section
						  2940.11 does not require arc-rated
						  protection for exposures of 2 cal/cm2 or less.
						  Untreated cotton clothing will reduce a 2-cal/cm2
						  exposure below the 1.2- to 1.5-cal/cm2 level
						  necessary to cause burn injury, and this material should not ignite at such low
						  heat energy levels. Although Section
						  2940.11(b)(2) does
						  not require clothing to have an arc rating when exposures are 2
						  cal/cm2 or less, Section
						  2940.11(b)(1)
						  requires the outer layer of clothing to be flame resistant under certain
						  conditions, even when the estimated incident heat energy is less than 2
						  cal/cm2, as discussed later in this appendix.
Additionally, it is especially important to ensure that
						  employees do not wear undergarments made from fabrics listed in Section
						  2940.6(j) even
						  when the outer layer is flame resistant or arc rated. These fabrics can melt or
						  ignite easily when an electric arc occurs. Logos and name tags made from
						  non-flame-resistant material can adversely affect the arc rating or the flame
						  resistant characteristics of arc-rated or flame resistant clothing. Such logos
						  and name tags may violate Section
						  2940.11(b), (b)(1), or
						  (b)(2).
Subsection (b)(2) of Section
						  2940.11 requires that arc-rated
						  protection cover the employee's entire body, with limited exceptions for the
						  employee's hands, feet, face, and head. Subsection (b)(2)(A) of Section
						  2940.11 provides that arc-rated
						  protection is not necessary for the employee's hands under the following
						  conditions:
For any estimated incident heat
								  energy
When the employee is wearing rubber insulating gloves with
								  protectors.
If the estimated incident heat energy does not
								  exceed 14 cal/cm2
When the employee is
								  wearing heavy-duty leather work gloves with a weight of at least 407 gm/m2 (12
								  oz/yd2).
Subsection (b)(2)(B) of Section
						  2940.11 provides that arc-rated
						  protection is not necessary for the employee's feet when the employee is
						  wearing heavy-duty work shoes or boots. Finally, Section
						  2940.11(b)(2)(C), (b)(2)(D), and
						  (b)(2)(E) require arc-rated head and face
						  protection as follows:
Minimum head
								  and face protection
Exposure
None
*
Arc-rated
								  faceshield with a minimum rating of 8
								  cal/cm
2*
Arc-rated
								  hood or faceshield with balaclava
Single-phase, open air
2-8
								  cal/cm2
9-12
								  cal/cm2
13
								  cal/cm2 or higher [DAGGER].
Three-phase
2-4
								  cal/cm2
5-8
								  cal/cm2
9 cal/cm2
								  or higher [DOUBLE DAGGER].
* These ranges assume that employees are wearing
						  hardhats meeting the specifications in Section
						  3381, as applicable.
[DAGGER] The arc rating shall be a minimum of 4
						  cal/cm2 less than the estimated incident energy.
						  Note that Section
						  2940.11(b)(2)(E)
						  permits this type of head and face protection, with a minimum arc rating of 4
						  cal/cm2 less than the estimated incident energy, at
						  any incident energy level.
[DOUBLE DAGGER] Note that Section
						  2940.11(a)(5)
						  permits this type of head and face protection at any incident energy
						  level.
IV. Protection Against Ignition
Subsection (b) of Section
						  2940.11 prohibits clothing that
						  could melt onto an employee's skin or that could ignite and continue to burn
						  when exposed to flames or to the available heat energy estimated by the
						  employer under Section
						  2940.11(a)(2).
						  Meltable fabrics, such as acetate, nylon, polyester, and polypropylene, even in
						  blends, shall be avoided. When these fibers melt, they can adhere to the skin,
						  thereby transferring heat rapidly, exacerbating burns, and complicating
						  treatment. These outcomes can result even if the meltable fabric is not
						  directly next to the skin. The remainder of this section focuses on the
						  prevention of ignition.
Section
						  2940.11(b)(2)
						  generally requires protective clothing and other protective equipment with an
						  arc rating greater than or equal to the employer's estimate of available heat
						  energy. As explained earlier in this appendix, untreated cotton is usually
						  acceptable for exposures of 2 cal/cm2 or less. [FN6]
						  If the exposure is greater than that, the employee generally shall wear
						  flame-resistant clothing with a suitable arc rating in accordance with Section
						  2940.11(b)(1) and
						  (b)(2). However, even if an employee is
						  wearing a layer of flame-resistant clothing, there are circumstances under
						  which flammable layers of clothing would be uncovered, and an electric arc
						  could ignite them. For example, clothing ignition is possible if the employee
						  is wearing flammable clothing under the flame-resistant clothing and the
						  underlayer is uncovered because of an opening in the flame-resistant clothing.
						  Thus, for purposes of Section
						  2940.11(b), it is
						  important for the employer to consider the possibility of clothing ignition
						  even when an employee is wearing flame-resistant clothing with a suitable arc
						  rating.
Under Section
						  2940.6(j),
						  employees may not wear flammable clothing in conjunction with flame-resistant
						  clothing if the flammable clothing poses an ignition hazard. [FN7] Although
						  outer flame-resistant layers may not have openings that expose flammable inner
						  layers, when an outer flame-resistant layer would be unable to resist
						  breakopen, [FN8] the next (inner) layer shall be flame-resistant if it could
						  ignite.
Non-flame-resistant clothing can ignite even when the
						  heat energy from an electric arc is insufficient to ignite the clothing. For
						  example, nearby flames can ignite an employee's clothing; and, even in the
						  absence of flames, electric arcs pose ignition hazards beyond the hazard of
						  ignition from incident energy under certain conditions. In addition to
						  requiring flame-resistant clothing when the estimated incident energy exceeds
						  2.0 cal/cm2, Section
						  2940.11(b)(1)
						  requires flame-resistant clothing when: The employee is exposed to contact with
						  energized circuit parts operating at more than 600 volts [Section
						  2940.11(b)(1)(A)],
						  an electric arc could ignite flammable material in the work area that, in turn,
						  could ignite the employee's clothing [Section
						  2940.11(b)(1)(B)],
						  and molten metal or electric arcs from faulted conductors in the work area
						  could ignite the employee's clothing [Section
						  2940.11(b)(1)(C)]
						  . For example, grounding conductors can become a source of heat energy if they
						  cannot carry fault current without failure. The employer shall consider these
						  possible sources of electric arcs [FN9] in determining whether the employee's
						  clothing could ignite under Section
						  2940.11(b)(1)(C).[FN1]
Flame-resistant clothing includes clothing that is
						  inherently flame resistant and clothing chemically treated with a flame
						  retardant. (See ASTM F1506-10a, Standard Performance Specification for Flame
						  Resistant Textile Materials for Wearing Apparel for Use by Electrical Workers
						  Exposed to Momentary Electric Arc and Related Thermal Hazards, and ASTM
						  F1891-12 Standard Specification for Arc and Flame Resistant
						  Rainwear.)[FN2]
The Department of Labor, Occupational Safety and Health
						  Administration used metric values to calculate the clearing times in Table 6
						  and Table 7. An employer may use English units to calculate clearing times
						  instead even though the results will differ slightly.[FN3]
The Department of Labor, Occupational Safety and Health
						  Administration based this assumption, which is more conservative than the arc
						  length specified in Table 5, on Table 410-2 of the 2012 NESC.[FN4]
The dielectric strength of air is about 10 kilovolts
						  for every 25.4 millimeters (1 inch). Thus, the employer can estimate the arc
						  length in millimeters to be the phase-to-ground voltage in kilovolts multiplied
						  by 2.54 (or voltage (in kilovolts) x 2.54).[FN5]
ASTM F1506-10a defines "arc thermal performance value"
						  as "the incident energy on a material or a multilayer system of materials that
						  results in a 50% probability that sufficient heat transfer through the tested
						  specimen is predicted to cause the onset of a second-degree skin burn injury
						  based on the Stoll [footnote] curve, cal/cm2." The
						  footnote to this definition reads: "Derived from: Stoll, A. M., and Chianta, M.
						  A., 'Method and Rating System for Evaluations of Thermal Protection,' Aerospace
						  Medicine, Vol 40, 1969, pp. 1232-1238 and Stoll, A. M., and Chianta, M. A.,
						  'Heat Transfer through Fabrics as Related to Thermal Injury,' Transactions-New
						  York Academy of Sciences, Vol 33(7), Nov. 1971, pp. 649-670."[FN6]
See Section
						  2940.11(a)(4)(A), (a)(4)(B), and
						  (a)(4)(C) for conditions under which
						  employees shall wear flame-resistant clothing as the outer layer of clothing
						  even when the incident heat energy does not exceed 2
						  cal/cm2.[FN7]
Subsection (a)(3) of Section
						  2940.11 prohibits clothing that
						  could ignite and continue to burn when exposed to the heat energy estimated
						  under subsection (a)(2) of that section.[FN8]
Breakopen occurs when a hole, tear, or crack develops
						  in the exposed fabric such that the fabric no longer effectively blocks
						  incident heat energy.[FN9]
Static wires and pole grounds are examples of grounding
						  conductors that might not be capable of carrying fault current without failure.
						  Grounds that can carry the maximum available fault current are not a concern,
						  and employers need not consider such grounds a possible electric arc
						  source.
1. New
						  Appendix D filed 2-27-2018; operative 4-1-2018 (Register 2018, No.
						  9).
Note: Authority cited: Section
							 142.3, Labor
							 Code. Reference: Section
							 142.3, Labor
							 Code.