This is the second of three columns inspired by a webinar I did for Mission Criticalon August 22. After that webinar I thought it would be helpful to publish some FAQs about the subject of safety. I’ve also added some questions asked by our audience during and after the event. The first of these columns covered topics related to initiating shock safety programs.

Electrical failure costs U.S. businesses billions of dollars each year; many of these incidents, however, are avoidable. Aside from the business disruption, these incidents take a horrific human toll. People injured or killed in these events came to work with the best of intentions and planned to go home in one piece at the end of their shift.

To successfully avoid electrical failures, though, businesses need to be proactive when it comes to electrical safety. Education is one of the most effective tools, but education is not a one-time event. Education is the underpinning of a comprehensive program.

Electrical shock and arc flash are the two primary types of electrical safety hazards in the workplace.

Electrical shock occurs when the human body becomes part of an energized electrical circuit. The degree of injury is directly related to the path the current takes through the body. As little as 1 milliamp is enough to cause death.

Arc flash is a fireball that occurs when an energized conductor is unintentionally connected to another energized conductor or ground. The air within the sphere of the established arc becomes conductive, and the arc grows exponentially until such time as current is interrupted.

Question: What is arc flash?

Answer:Arc flash is a fireball that can develop when an energized electrical conductor comes in contact with another energized conductor or ground. Visualize a welder striking a controlled arc. Now imagine that arc unleashed on steroids. The temperature of an arc flash is approximately 35,000ºF (the surface of the sun is about 10,000ºF). The material consumed in the arc flash physically expands 70,000 times. This fireball travels a speed of 5,000 fps, with a face pressure of 500 lbs psi and a sound level of 160 db.

fig 1

Appropriate PPE for different hazard levels

Question:How is the arc-flash hazard level measured?

Answer:A systematic study called an arc flash hazard analysis must be conducted by a safety professional. This study reviews the entire electrical infrastructure to determine the energy available at any access point (removable covers or doors) in the system. Available energy depends on many factors such as the size, type, voltage, and ampacity of transformers, interconnecting cable size, type and impedance, type of over-current protective, and their ratings or settings, etc.

The available energy at any access point is expressed as incident energy. Available incident energy is calculated based upon a person standing directly in front of the potential arc flash source at 18 in. (18 in. being the average length of a person’s forearm). Incident energy is measured in calories per centimeter squared (cal/cm²). The amount of available incident energy determines the category of a potential arc-flash hazard faced at that point in the system. Any future changes in the electrical infrastructure may change the arc-flash analysis. Facilities managers should review and update arc-flash analysis whenever upgrades, repairs, or modifications are made to the electrical infrastructure.


Question:What are arc-flash hazard categories?

Answer:These are simply numbers representing the degree of hazard based on a range of incident energy. The table lists the incident energy range and the category hazard.

table 1

Energy levels at differnet hazard risk categories.

Question:What is PPE?

Answer:PPE stands for personal protective equipment (see the figure). PPE is specifically rated for its ability to protect an individual according to the arc-flash hazard faced. A PPE kit is normally issued to each individual who will perform electrical maintenance or repair.

 A basic kit for hazard class 1 to 4 consists of the following items:

• Compact first aid kit

• Eye dressing kit

• Ear plugs

• Safety glasses

• Portable GFCI

• Safety triangle kit

• Lock out/tag out (LOTO) tags

• Lockout hasp

• Multi-pole breaker lockout hasp

• Large breaker lockout

• Green LOTO padlock 1 ½-in. shackle

• Summer cotton glove liner

• 40-cal coat and overalls

• 40-cal arc flash gloves

• 40-cal arc flash hood / helmet

• 40-cal equipment storage bag

• 11-cal hood, hard hat, face shield, and storage bag

• 11-cal high visibility safety vest

• 11-cal arc flash gloves

• Insulating mat

• Insulating mat clamp and pin

• Fire extinguisher

• Rubber insulating gloves

• Glove storage bag

• Leather protective gloves

• Molded sleeves

• Molded sleeve harness

• Molded sleeping bag


Question:What is the average cost of providing PPE for my staff?

Answer:Based on the list above, a PPE kit will cost between $3,000 and $3,500 per kit.


Question:What is meant by LOTO?

Answer:LOTO refers to the procedures and hardware used to secure de-energized electrical equipment. Dedicated locks and identification tags are applied by allpersons working on de-energized equipment. This process ensures that the equipment or circuit being worked on will remain de-energized until all team members remove their locking device and tag. No one may remove another’s lock and tag.

Some facilities will employ a single department lock and tag with the key secured in a metal box to which all team members’ locks are applied vs. placing multiple locks and tags directly to the gear.

Electrical safety is not an option. This topic is broad and complex and requires the allocation of significant resources to establish a comprehensive program. Four to five injuries or deaths occur each day in the U.S. as a result of electrical shock or arc flash. You can debate the difference between standards and statutes; however the standards are the basis for statutes and codes.

One industry study concludes the minimum cost of an arc flash event is $750,000. I would submit that it is likely to be a lot higher when you consider the direct damage to the equipment and facility, the liability as a result of injury or death, and the business disruption. As a facility manager, you could be held personally liable in the event of an incident if you fail to enforce safe work practices for your employees and contractors. In a court of law or the court of public opinion, you’ll fare much better having done the right thing. It’s time to get serious about electrical safety in every facility. Protect your employees, your contractors, and your company.