Understanding the requirements for Arc Flash PPE can be confusing and often misunderstood. In this article I am going to review the requirements and why they exist. First, let’s understand why there are requirements in the first place. Before reading further it might help to download the latest PPE Chart as a guide.
NFPA 70E section 130.7(C )(1) requires all workers within the flash protection boundary to wear PPE. How much and what type of PPE depends on the hazard. Let’s remember that the purpose of this is to protect anyone working on live electrical equipment from injury or death in the event of an arc flash incident.
The folks that write the standard are fully aware of the purpose. They realize that too little PPE exposes a worker to serious injury or death. They also realize that high levels of PPE are bulky, cumbersome, and hot. These high levels also restrict hearing and field of vision and make the tools hard to handle. This can not only increase the difficulty of the task, but also introduce other safety hazards.
For this purpose NFPA 70E has provided 5 levels of protection. Most of these levels require protection that is easy to work in. They leave the most cumbersome PPE for only those hopefully rare occasions when you would work on extremely high energy electrical equipment in a live state. This is why NFPA 70E and any solid electrical safety program recommends working de-energized as much as possible.
Calories and Levels of PPE
All PPE is rated in calories. Calories/cm2 is a unit of heat and energy. This is how all potential arc flash events are measured. A compliant arc flash label will show a value in cal/cm2 on the label. This is called incident energy and it tells a worker how much PPE should be worn for protection. The higher the value the higher the risk.
NFPA 70E has created 5 risk categories that are all based on the incident energy (cal/cm2). This is shown in the following table.
Level Incident energy
0 0 cal/cm2
1 4 cal/cm2
2 8 cal/cm2
3 25 cal/cm2
4 40 cal/cm2
The level of arc flash should also be on the arc flash label. A worker can use the level or incident energy on the label to determine risk and PPE. If you are to work energized on an electrical panel that has an arc flash PPE Level l with an incident energy of 3 cal/cm2 you will need to suit up to PPE providing up to 4 calories of protection. Furthermore if the label states Level III you will need a 25 cal/cm2 suit.
Again, the reason for so many levels and categories is too aid the worker. We don’t want you wearing a giant space suit if the risk doesn’t warrant it.
Clothing refers to the garments required for the risk category. It refers to shirt, pants, shoes, coveralls, etc. Arc Flash clothing is rated in cal/cm2 to help you choose the proper protection. The clothing should meet ASTM F1506 approval to be considered fire retardant and safe. Be sure to identify this approval when purchasing. In addition, you will want to check the laundering methods and how they affect the FR rating of the garment. The supplier should be able to guide you on this. Below is a table covering the requirements. The letters FR refer to fire resistant meaning that the garment will self-extinguish once the fire ceases.
|Hazard/Risk Category||Clothing Description||Required Minimum Clothing Arc Rating|
|0||Non-melting, flammable material
with fabric weight of at least 4.5 oz/yd2
|1||Arc-rated FR shirt + FR pants or FR coveralls||4 calories/cm²|
|2||Arc-rated FR shirt + FR pants or FR coveralls||8 calories/cm²|
|3||Arc-rated FR shirt + FR pants or FR coveralls, and Arc-rated flash suit, the layered system must meet the required minimum rating.||25 calories/cm²|
|4||Arc-rated FR shirt + FR pants or FR coveralls, and Arc-rated flash suit, the layered system must meet the required minimum rating.||40 calories/cm²|
Arc flash equipment refers to face shields, hard hats, hearing protection, eye protection and gloves. There are also requirements for equipment that go along with each risk level. It’s not enough in many instances to just have FR rated clothing. We also want to protect our hands, face and head from exposure. This is summarized in the following table. Remember that face and head protection also has a calorie rating.
|Eye protection, ear canal inserts, long sleeve shirt and pants||Arc rated clothing||Face & Head Protection||Flash Suit Hood|
Confused yet? Me too. That’s why we’ve put it together in one easy to follow table for you. Click here to download the table. Many facilities find it helpful to print out a chart like the one below to hang in the electrical rooms and maintenance shop.
Hopefully the above tables helped explain it in a step-by-step manner to get you to this point. However, the table below provides an overview of the calories, category level, clothing and equipment. It should be all you need to make a decision on protection.
One Final Note
At first glance these charts can be confusing. The first reaction by many is that from this point forward you will need to wear something equivalent to a space suit every time you work on electrical equipment. In reality it’s not as bad as it seems.
The overwhelming majority of electrical equipment falls in the ranges between Level 0 and Level II. These require protection up to 0, 4 and 8 cal/cm2 respectively. Clothing with an 8 cal/cm2 rating is not cumbersome to work in. Our workers including myself work in 8 calorie clothing full time when we are on-site collecting data. It does not restrict movement or prevent you from doing anything you can’t do with everyday clothing on.
The rest of your electrical system, and in most cases this is usually the overwhelming minority, is rated at category III or IV. In these cases you will need to suit up to either 25 or 40 calories. This is where it becomes hot, tedious and cumbersome.
Let me repeat. In most facilities these levels constitute a minority of the electrical system and the PPE doesn’t even apply if you are working de-energized. What this means is that in most cases it is a rare occurrence that you would be interacting with live electrical equipment above a category level II. However, in those rare instances isn’t it worth the time to protect yourself? It only takes one incident to change or end your life.