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Electrical Arc Blasts and How it Concerns You

It has been estimated that in the United States alone there are approximately 5-10 arc flash explosions per day, and in a recent study there were an estimated 360 deaths linked to the explosions in a single year. That is basically a death every day.

Electrical Arc Explosions have been a growing concern for management, safety directors, and of course the employee involved, as well as their family. It is important that all parties stay up-to-date on the latest news, and be compliant when working in these extremely hazardous conditions.

An arc flash is basically a short circuit. This flash is normally a fraction of a second, but the thermal radiation it produces can reach temperatures well over 20,000°F under the right circumstances. There can be countless contributors to this. It can be human error when working with energized circuits causing phase-to-ground or phase-to-phase faults or equipment failure.

OSHA has not made a law concerning this, but many companies have been fined over the years under the General Duty Clause. The General Duty Clause states:

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 . . . .’

The Occupational Safety & Health Administration (OSHA) and National Fire Protection Agency (NFPA) have recently stepped in to help make working conditions safer. The standard is known as NFPA 70E, and has been revised in 2004 (NFPA 70E-2004). The complete standard may be purchased at in book form or downloaded as a document for viewing on a computer screen.

What is a calorie? And what does it have to do with me? A calorie is a measurement of energy. The actual definition is calories per centimeter squared (cal/cm²). If there is an arc flash, a specific cal/cm² can be determined beforehand to protect the employee from injury. Obviously, the goal of the standard is to prevent a second-degree burn on any part of the body of an employee. A second-degree burn begins around 1.2 cal/cm². A good explanation of a second-degree burn would be to use a butane lighter and place the hottest part of the flame under your thumb for one (1) second. The result would be a 1.2 cal/cm² burn, or second-degree burn.

There are a many Hazard Risk Categories (HRC), the primary ones being HRC 1, 2, 3 and 4. Each respectively represent a cal/cm² rating of 5, 8, 25 and 40. By knowing your calorie rating at each job location, the Hazard Risk Category can be assessed. This is important when ordering the proper PPE from your local distributor. Within HRC 2, there is sub-category 2*. Sub-category 2* requires the use of a beekeepers style switching hood rather than a flip-down style shield. This is important for specific job functions, as similar jobs may change slightly.

Before work is performed on energized equipment, a flash hazard risk analysis is mandatory. It must be in accordance to OSHA 29 CFR 1910.132(d)(1) which basically states that an employer is required to provide acceptable equipment and proper protective clothing.

Testing for product compliance is an ongoing process for us as a manufacturer of arc clothing. This testing is primarily conducted in Toronto at Kinetrics Laboratory. During a recent visit to Kinetrics, I witnessed first hand the dangers that can be associated with arc flash. The wrong protective clothing can result in severe injuries, and even death. We have received many calls and notes over the years from end users of our product relaying their survival testimonies.

The NFPA 70E-2004 tables are a great source to determine the proper protective clothing needed. It will also inform the voltage rated gloves and tools required for the job to be performed, along with setting safe approach boundaries. Remember, a hazard risk analysis must be performed for each job location! Variances such as current change and clearing times can be different at the same facility within the same system. This could dramatically change the clothing needed for a safe working environment.

General questions we are asked on a daily basis are “What clothing do I need to conform to the Standard?” or “I am working with xxx volts, what Hazard Risk Category does this put me in?” It is a bit more complicated than this, but not by much! There are numerous ways to come to a logical answer. The easy way is to hire a consultant to come onsite and perform the analysis. By doing this, they will go to each location, review the jobs being performed and give the proper assessment for said location. There are also a few software programs available, as well as tables in the NFPA 70E book which tend to be the most popular choice for safety directors.

Table 130.7(C)(11) in the NFPA 70E Standard shows the typical protective clothing systems for their associated Hazard/Risk Categories. These are listed as Category 0 thru 4 as mentioned previously. After a hazard risk analysis is performed, this table should be used to decide which clothing combinations are required. Keep in mind this is the minimum requirement of Personal Protective Equipment (PPE) and excess in this case is acceptable.

A simplified version on finding the proper PPE is to follow Annex H, which can be found in the NFPA 70E-2004 Standard. This is a simplified two-category flame resistant clothing system. It is not a part of the requirements, but is included for informational purposes only. This system is an approach for facilities with diverse electrical systems. Again, a risk analysis should always be performed and this is sometimes overlooked when an organization sees this as an easy solution. This approach has two sets of clothing in different Hazard/Risk Categories for use in different situations. It has Everyday Work Clothing and Electrical “Switching” Clothing.

Stanco Safety Products has been involved in extensive testing and new product development for Arc Flash Clothing, with some exciting new products that enhance safety and comfort! Please contact us with any questions you have concerning Electrical Arc Safety to discuss your options. We can customize a solution to fit the needs of your company. See us on the web at