Electricity plays such an intimate role in our daily lives that it is very often overlooked as a lethal hazard, even by those who should know better.   The use of electricity has brought many benefits and has lightened the physical load for many workers.   However, electricity is definitely an energy source with the potential to cause serious harm or death.

The scope of this article covers protection from electrical shock hazards only. While the subjects of arc flash and arc blast are every bit as important and the hazard and every bit as lethal as electrocution, they will not be covered in this article.

To understand the terms and properties, electricity can be compared to the flow of water through a pipe.   The water pressure is analogous to voltage, which is the driving force, and the water flow is analogous to current, which is the flow of electrons in a conductor.   The pipe wall is analogous to the insulating covering on a conductor.   The flow of electrons is much the same as the flow of water, always seeking the lowest level or ground.

Ohm’s Law governs the current passing through a circuit.   Current “i” measured in amperes is equal to the voltage “v” measured in volts divided by resistance “r” measured in ohms or i=v/r.   The higher the resistance of a circuit the lower the current that will pass at any given voltage.   A high quality rubber or plastic film presents a very high resistance, and most metals present a very low resistance.   Human skin when dry and unbroken has a relatively high resistance, where as perspiration or blood present a relatively low resistance.   Water and wet earth have very low resistance.

What does electricity do when it finds a path through the human body?    Table 1 gives some effects of increasing current levels passing through the human body.

Table 1 - Overview of Electrical Hazards

CURRENT LEVEL	EFFECTS OF CURRENT
1 milliampere	Barely perceptible
16 milliampere	Maximum current an average man can grasp and “let go”
20 milliampere	Paralysis of respiratory muscles
100 milliampere	Ventricular fibrillation threshold
2 ampere	Cardiac standstill and internal organ damage

Electrical hazards to the human body can result from a number of conditions:

• Current passing through the hand and arm muscles may cause involuntary constriction resulting in the inability to “let go”
• Current passing through the body may interfere with heart and respiratory functions
• Current passing through the body may result in enough heat to cause burns
• Arcing of electrical current through the air may create a flash generating high levels of light and heat so as to seriously damage skin, flesh or eyes
• Arcing of electrical current through the air may create a blast that can do physical damage
• Falls as a result involuntary movement caused by contact with electrical shock

Contact with points of voltage can be direct or indirect.   A direct contact is the contact of the body with the conductor.   Indirect contact results when something that is being held or touched is in turn in contact with the conductor.   If this indirect contact is able to conduct electricity there is a potential for the current to flow through the holder to ground.

OSHA has addressed electrical hazards by issuing a set of standards.   These standards are found in 29CFR1910, Sub Part S, 1910.331 – 1910.335 “Electrical - Safety-Related Work Practices” and 1910.137 “Personal Protective Devices” Sub Part “Electrical protective devices”. The topics dealing with work practices are as follows:

1910.331 - Scope

1910.332 - Training

1910.333 - Selection and use of work practices

1910.334 - Use of equipment.

1910.335 - Safeguards for personnel protection.

1910.333 (a) states “General - Safety-related work practices shall be employed to prevent electric shock or other injuries resulting from either direct or indirect electrical contacts, when work is performed near or on equipment or circuits which are or may be energized. The specific safety-related work practices shall be consistent with the nature and extent of the associated electrical hazards.

1910.333 (a)(1) states "Deenergized parts." Live parts to which an employee may be exposed shall be deenergized before the employee works on or near them, unless the employer can demonstrate that deenergizing 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 deenergized if there will be no increased exposure to electrical burns or to explosion due to electric arcs.

This section establishes that voltages over 50 volts are to be considered hazardous.   It also establishes criteria for working on energized parts.   Section (b) of 1910.333 mandates the use of Tag Out Lock Out procedures for insuring the safety or employees working on deenergized parts.   Section (c) of 1910.333 deals with "Working on or near exposed energized parts."

1910.333 (c)(2) states

"Work on energized equipment." Only qualified persons may work on electric circuit parts or equipment that have not been deenergized under the procedures of paragraph (b) of this section. Such persons shall be capable of working safely on energized circuits and shall be familiar with the proper use of special precautionary techniques, personal protective equipment, insulating and shielding materials, and insulated tools.”

The personal protective equipment includes insulating rubber gloves, which are detailed in 1910.137. The standard does not mandate the use of insulating rubber gloves but quite often they are the most practical approach to working safely on energized circuits.   These gloves are available in six different working voltage classes.   The higher the voltage protection the thicker the gloves. The maximum test current allowable is stated in milliamps and is for the shortest glove in each class. These classes are listed in Table 2.

  Table 2

CLASS	WORKING VOLTAGE	TEST VOLTAGE	MAXIMUM CURRENT	LABEL COLOR
CLASS 00	500 VOLTS AC	2,500 VOLTS AC	8 ma – 11 inch	BEIGE
CLASS 0	1,000 VOLTS AC	5,000 VOLTS AC	8 ma – 11 inch	RED
CLASS 1	7,500 VOLTS AC	10,000 VOLTS AC	14 ma – 14 inch	WHITE
CLASS 2	17,000 VOLTS AC	20,000 VOLTS AC	16 ma – 14 inch	YELLOW
CLASS 3	26,500 VOLTS AC	30,000 VOLTS AC	18 ma – 14 inch	GREEN
CLASS 4	36,000 VOLTS AC	40,000 VOLTS AC	22 ma – 16 inch	ORANGE

The gloves must be manufactured and tested in accordance with OSHA 1910.137 part ‘a’. This standard relies heavily on the American Society for Testing and Materials, ASTM D-120   “Standard Specification for Rubber Insulating Gloves”.   The OSHA 1910.137 part ‘b’ addresses the in-service care and use of Electrical Protective Devices and requires training in the care and use of these devices.   The standard also requires regular visual inspection, periodic electrical re-testing and the use of leather protector gloves when cut, abrasion or puncture of the rubber,   insulating glove is likely.

Rubber insulating gloves are rated according to the maximum working voltage and type. There are two types, Type I gloves are not resistant to Ozone and Type II gloves are resistant to Ozone.   Table 2 shows the current OSHA and ASTM designations for voltage rating.   Please note that OSHA 1910.137 does not include the Class 00 while ASTM D120 does.   OSHA considers the use of the class 00 glove for protection against electrical shock hazards of 500 volts or less, a de minimis violation. De minimis violations are violations of existing OSHA standards, which have no direct or immediate relationship to safety or health. Such violations of the OSHA standards result in no citation, no penalty and no required abatement.   OSHA has indicated that when the review of the 1910.137 standard takes please, the Class 00 will be included.

Electrical insulating gloves are subjected to lot testing immediately after manufacturing.   These lot tests are destructive and test certain mechanical and electrical properties of a prescribed number of gloves from each production lot.   Each individual glove is subjected to a thorough visual inspection under inflation and electrically tested according to the voltage levels in Table 2.   Once gloves are tested they must be put into service within one year or re-testing is required.   Once in service gloves must be electrically re-tested every six months there after.   Any time an event occurs that is thought to have caused harm to the insulating gloves, use of the gloves should be discontinued immediately and they should be turned in for re-testing.   The telecommunications industry has a slightly different re-test requirement as spelled out in 1910.268(f)(2) & (f)(3):

1910.268 (f)

(f)(1)

Rubber insulating equipment designed for the voltage levels to be encountered shall be provided and the employer shall ensure that they are used by employees as required by this section. The requirements of § 1910.137, Electrical Protective Equipment, shall be followed except for Table I-6.

(f)(2)

The employer is responsible for the periodic retesting of all insulating gloves, blankets, and other rubber insulating equipment. This retesting shall be electrical, visual and mechanical. The following maximum retesting intervals shall apply:

Gloves, blankets, and other insulating equipment	Natural rubber Months	Synthetic rubber Months
New	12	18
Re-issued	9	15

(f)(3)

Gloves and blankets shall be marked to indicate compliance with the retest schedule, and shall be marked with the date the next test is due. Gloves found to be defective in the field or by the tests set forth in paragraph (f)(5) of this section shall be destroyed by cutting them open from the finger to the gauntlet.

The following additional ASTM Standards are useful in determining a complete program of safe work procedures and training when using insulating rubber devices:

ASTM F496 – “Standard Specification for In-Service Care and User of Insulating Rubber Gloves and Sleeves”

ASTM F696 – “Standard Specification for Leather Protectors for Rubber Insulating Gloves and Mittens”

ASTM F1236 – “Standard Guide for Visual Inspection of Electrical Protective Rubber Products”

The identification and classification of hazards in the workplace requires a formal and organized effort on the part of employers.   Workers must be trained in recognizing these hazards, in the application of work practices and in the use of special tools and techniques to safely do their jobs.   Personal protective equipment must be properly specified and workers trained in the care and use of this PPE.   No worker should ever be put at risk in order to complete their job.   The effort required to develop a good safety program is minimal against the valuable assets they are designed to protect - your workers. The National Fire Protection Association (NFPA) makes available a “Standard for Electrical Safety Requirements for Employee Workplaces” (NFPA 70E) and “The Electrical Safety Program Book”, which will help in developing proper safety guidelines for employees who are at risk due to electrical hazards.

Paul Gelinas is Vice President of Comasec Safety, Inc. located in Enfield,.CT. Comasec Safety, a member of Comasec International, offers a range of gloves for personal protection including the low voltage Linemen’s Gloves.

i. Endnote. Table 1. “Overview of Electrical Hazards” by Virgil Caisini, BS downloaded from the NIOSH web site, http://www.cdc.gov/niosh/elecovrv.html