An arc flash is a part of an arc fault, which is an electrical issue where electricity is discharged from its normal path due to a connection of low-impedance. The electricity travels from the source (often wires or machines) through the air to the ground or another destination. Arc flashes are extremely dangerous because they are so powerful and they occur so quickly it is impossible to react to them or take cover.
Since it is impossible to react to an arc flash, it is important to put safety systems in place to minimize the risk of them occurring and minimize the potential injury to those in the area. One of the most effective options is to ensure all employees working near these hazards wear personal protective equipment (PPE).
When Is Personal Protective Equipment Required?
Most facilities use the National Fire Protection Association (NFPA) 70E standards to determine when specific PPE is required for working with electrical equipment. This set of standards provides a lot of detail about what type of PPE is needed and when the employees should wear it. Staying in compliance with these standards can help protect employees. There are many key points to remember from NFPA 70E, but the approach boundaries are typically seen as the most critical.
The most effective way to keep people safe from arc flashes is to ensure they do not enter an area where there is a higher risk of an arc flash occurring. The NFPA has created a series of boundaries to alert people to the potential risks and ensure they stay away from them. These boundaries identify how far away people should stay based on the amount of risk present.
There are several levels of approach boundaries to be aware of.
NFPA Limited Approach Boundary
The limited approach boundary is identified by NFPA as "a shock protection boundary" that should only be crossed by those who are trained and qualified. This boundary should also only be crossed in situations where someone needs to perform a specific task in that area. People should never walk through this area just for convenience, even if they are trained on working with electrical equipment.
Ideally there should be either a physical boundary (a fence, for example) or at least a visual boundary such as floor marking tape or a safety sign. The 2015 NFPA updates provide some clarity to the positioning of barricades. The NFPA specifically states that these barricades cannot be put any closer than this limited approach boundary.
The specific distance from an electrical hazard where the limited approach boundary is located is based on the voltage of the equipment.
NFPA Restricted Approach Boundary
Entering a restricted approach boundary area is even more dangerous because it is closer to the source of the danger. As with the limited approach area, this location should be restricted to only people who have gone through the proper training.
Personal protective equipment is required for anyone entering this area, and these individuals will typically require a higher level of PPE in order to enter. Whenever working within the restricted approach boundary, employees must use insulated tools. This requirement used to be set at the limited approach boundary, but as of 2015, NFPA has adjusted this to the restricted approach boundary.
Before entering a restricted approach boundary area, the individual must get written approval for the plan of what they will be doing. The plan must also cover the requirements to make sure the employee keeps all body parts out of the prohibited approach boundary.
NFPA Prohibited Approach Boundary
You may hear people talk about the NFPA prohibited approach boundary in some situations. This boundary is from an older standard that was actually eliminated in the 2015 updates released by the NFPA. Going forward, it should not be used at all; however, some facilities do still use it or refer to it, so it is a good idea to at least be familiar with what the NFPA prohibited approach boundary was when it was still officially in place.
The prohibited approach boundary referred to any area that must be treated as if the person was coming into direct contact with the electrified part of the machine. As with the other boundaries, only those who have had the proper training should enter, and approval of the plan must be received before anyone even approaches these areas.
NFPA Arc Flash Boundary
An arc flash boundary is not the same type of boundary as the others mentioned above. Instead, this boundary is the distance at which an arc flash is dangerous should one occur. Specifically, this boundary is defined as a distance where a person in the area is exposed to 1.2 cal/cm squared of energy. This is calculated by looking at the voltage and the total fault exposure levels. If an arc flash occurred and someone was within the arc flash boundary, it is possible the electricity would pass through that person, causing extreme burns and possible death.
Anyone who needs to go within an arc flash boundary needs to wear the level of personal protective equipment needed based on the voltage in the machine being worked on. The arc flash boundary is typically somewhere outside of the limited approach boundary.
Arc Flash PPE Category Levels
Personal protective equipment for arc flash is broken up into a total of four categories ranging from 1 to 4. Level 1 contains the least PPE, while level 4 contains the most PPE.
These categories match up to the level of risk involved in a given situation. For example, if someone is working with low-voltage wiring that is not likely to create an arc flash, they will not need extensive PPE. If someone is working on a high-voltage machine where there is a serious risk of an arc flash, category four is likely going to be needed. The following is a breakdown of what each category of PPE includes.
Arc Flash PPE Category 1
The first level of PPE is necessary for energy levels up 4 cal/cm squared. This PPE is fire resistant and arc rated.
- Arc-rated long-sleeved shirt and pants (or a coverall)
- A hard hat with arc-rated face shield
- Hearing protection
- Safety goggles or glasses
- Leather gloves or another type of insulating gloves
- Leather shoes
Arc Flash PPE Category 2
Category 2 arc flash PPE is for situations where the energy level reaches up to 8 cal/cm squared.
Category 2 is quite similar to category 1. At this level, the arc-rated face shield should also include a sock balaclava. In general, the category 2 PPE should also be higher rated than the equipment used in category 1 situations.
Arc Flash PPE Category 3
Category 3 is a significant jump up in protection. It's for any areas where the energy level is up to 25 cal/cm squared. Category 3 requires multiple layers of fire-resistant, clothing including cotton undergarments. In addition to the items listed in category 2, employees should wear an arc flash suit jacket, suit pants, and suit hood, each of which should be arc rated at 25 cal/cm squared or above.
Arc Flash PPE Category 4
This is the highest level of arc flash personal protective equipment. It is used for any situation that has energy levels above 25 cal/cm squared. These are some of the most dangerous areas where an arc flash could easily kill people in a fraction of a second. The highest possible levels of protection should always be employed, even if the risk of an arc flash is low.
At category 4, the employees will need to wear all the same type of PPE as in category 3, except it should be rated at 40 cal/cm squared rather than 25. This is a big jump up and will provide the additional protection needed when working with high-voltage equipment.
Choosing the Right PPE
Determining when arc flash PPE is required and which category of PPE is necessary is not always as straightforward as many people would like. There are guidelines available from NFPA as part of the 70E standards that help employers and employees determine exactly what is required.
It is in the best interest of both the employer and the employee to have clear guidelines in place for determining which type of personal protective equipment is needed in every situation.
The following video provides an overview of how to determine which type of personal protective equipment is needed:
When employees need to act quickly to respond to or prevent an emergency situation, however, it can be difficult. A good rule of thumb for this type of urgent response is to use the highest category of personal protective equipment that could be required.
It is much better to wear a category 4 set of PPE when only a category 2 would actually be needed than it is to put on category 2 equipment when category 3 is actually needed.
Arc Flash PPE Training
Working with electrical equipment that could cause an arc flash can be very dangerous work. This is why there is so much training required to perform the work itself. In addition to becoming proficient at the actual work that needs to be done, employers should also provide employees with training on the proper use of arc flash personal protective equipment.
PPE cannot keep employees safe if they are not wearing it properly when an emergency occurs. Remember, an arc flash can create a blast that can throw an employee across the room and cause them to lose consciousness. Wearing PPE properly can mean the difference between minor injuries and a fatal accident.
Offering good training and regular review sessions to all employees who work with electrical equipment in a facility is extremely important. According to regulations, it is the responsibility of the employer to ensure everyone is properly trained before completing this type of work.
Storing Arc Flash Personal Protective Equipment
While some jobs require people to wear arc flash personal protective equipment on a regular basis, that is often not the case. In many facilities, this type of PPE will only be needed a couple times per year, or even less. When this is the case, it is important to ensure the equipment is stored in a way that is safe, yet accessible.
One of the first things to keep in mind when storing arc flash PPE is accessibility. In the event of an emergency, designated employees should be able to find and put on the PPE very quickly. Placing the PPE in a storage closet that is marked with a label on the outside can be a very effective option.
In addition to accessibility, it is important to keep this type of equipment safe. If the equipment gets a hole or tear in it, the safety of the person wearing it will be compromised. With this in mind, employers are responsible for inspecting the PPE on a regular basis to ensure there are no problems. If a hole or other issue is found, it needs to either be properly patched or replaced.