What is ATPV, and how is it used in your hazard assessment?
Put simply, ATPV—Arc Thermal Performance Value—is the most commonly reported test result of the effectiveness of FR clothing. It measures the amount of incident energy that your FR garment can protect you from before the onset of a 2nd degree burn. And the FR garments in your safety program must meet or exceed the Incident Energy required based on your hazard assessment. But it’s a bit more complicated than that.
To better understand ATPV, let’s start with an overview of two main concepts: The Stoll Curve and Arc Ratings.
The Stoll Curve
The Stoll Curve is the predictive model used to measure the probability of burn injury. It quantifies the heat levels and exposure times that result in a second-degree burn, including high temperature exposure for a short time and low temperature exposure for a much longer duration.
An arc rating is the protection level afforded by an FR fabric when exposed to an electric arc. The arc rating of a fabric is determined by exposing the fabric to a staged electrical arc. In real life, arc behavior can be unpredictable, so the testing requires samples be exposed to a “controlled” arc utilizing the ASTM 1959 standard.
That brings us to ATPV (Arc Thermal Performance Value), which is a type of arc rating. The ATPV of an FR garment indicates that you have a 50% chance of the onset of a 2nd degree burn if exposed to an electric arc with the same calories of incident energy. The fabric will usually not break open unless exposed to incident energy levels higher than the arc rating.
So why is ATPV important? Think about it this way:
Let’s go back to what ATPV measures:
The amount of incident energy that your FR garment can protect you from before the onset of a 2nd degree burn.
Why is that important?
• By definition, second-degree burns cause a blistering, blisters can break the skin (that’s why the test is designed around 2nd degree burns).
•One of the pathways to infection is broken skin.
• One of the causes of death in burn victims is infection.
When you think about it that way, matching the ATPV of the FR garments in your safety program to the value required by your hazard assessment is not just a matter of meeting the standards. For your guys, it can be the only thing that stands between them and a potentially life-threatening burn hazard.
To learn more about ATPV and Arc Ratings, download our whitepaper: Understanding Arc Ratings
You know you need to be wearing FR. And you know your FR clothing has to meet—or better yet, exceed—your required ATPV. A layered FR system is one great way to ensure you’re protected and keep you comfortable.
But FR layering can get tricky. It’s not as simple as adding up the arc ratings of each layer. For instance, the Bulwark Long Sleeve FR Two-Tone Base Layer- EXCEL FR® on its own carries an ATPV of 6.4 calories/cm². And the Deluxe Coverall – CoolTouch® 2 – 7 oz. carries an ATPV of 9.0 calories/cm² (KH). However, when combined as a layered FR system, the two garments have a layered arc rating of 21 calories/cm2 and a layered CAT rating of 2. As you can see, that’s significantly higher than the total ATPV if you simply combined the two garments’ arc ratings. This is the result of a number of factors, one of which is the additional layer of air between the layers that creates added insulation.
That brings us to another crucial aspect of FR layering, and one that causes a lot of confusion among safety professionals. Do the standards permit you to layer non-FR undergarments beneath your FR garments?
The answer, in short, is yes, if it is beneath the outer FR layer:
According to NFPA® 70E section 130.7 (C) (12) (a), non-melting flammable garments (i.e., non-FR) are permitted to be worn under FR garments for added protection.
In fact, as we demonstrated above, putting an extra layer of fabric between your skin and your outer FR layers can provide an added level of protection—even if the garment is not FR. It has the further benefit of absorbing perspiration to keep you drier and more comfortable in warmer months, while insulating you against the elements in cold weather. However, that layer—and the added protection it affords the wearer—will not count toward achieving the required arc rating of the complete FR layered system. Any protection it provides is considered above and beyond the ATPV already met by the FR garments.
It is also important to note that meltable fibers such as acetate, nylon, polyester, polypropylene, and spandex cannot be used in the layer closest to your skin. Because in the event of a flash fire or electric arc, some heat will inevitably pass through the outer layer of FR and cause a T-shirt to melt if it is made from synthetic materials like those fabrics mentioned above. The melting of these materials can significantly increase the burn injury. Undergarments made with natural fibers are permitted, as they will not add to the injury. However, that is assuming there is no break open of the outer layer and the outer layer is worn correctly (tucked-in), both of these scenarios could allow for the base layer made with natural fibers to ignite.
As such, when it comes to layering your FR, the best solution to maximize both safety and comfort is to opt for an FR base layer, like those offered by Bulwark. Our FR base layers are designed to wick moisture and keep you comfortable, while increasing your overall protection by eliminating the threat of ignition. And, since these FR base layers are arc rated, they can contribute to your overall layered system arc rating. Meaning you can achieve or even exceed your required protection level, often with a combination of lighter weight FR fabric.
To simplify the FR layering process, we worked with our very own FR experts to design the Bulwark Arc Rating Calculator—an online tool that allows you to quickly and simply determine the total system arc rating for over 400 combinations of Bulwark FR garments.
Cold stress may not be as well-known as heat stress, but when the temperature drops, it can pose a significant danger. Employers have many options for helping workers manage their exposure to cold while protecting them from flash fire and arc flash. This whitepaper discusses how you can layer FR/AR garments, how to implement a PPE program and the warnings signs of cold stress.
Fill out the form below to download the whitepaper.
When you think about establishing a successful FR clothing program, what “check list” items immediately spring to mind? Generally speaking, the first two mental steps people in this industry take are: 1.) Evaluating the thermal hazard you are providing protection for; and 2.) Selecting the appropriate FR garments for that hazard.
But for your FR program to be fully effective, you need to look beyond just choosing the right gear for the environment you and your crew are working in. You need to examine every layer closely, beginning with your base layers.
Fact is, an FR clothing program is not fully defined if it does not place restrictions or set guidelines on clothing to be worn under the FR uniform. In the worst circumstances, lack of guidance on base layer clothing can leave an employee at risk for injuries. Consider, for a moment, the extent of an injury that could be sustained by someone wearing a t-shirt made of synthetic fibers under their FR clothing. Sure, the outermost FR layer will self-extinguish in a thermal event. But enough thermal energy could transfer to the t-shirt underneath, causing it to melt to the wearer’s skin.
One simple way to manage this issue is to mandate that all undergarments be made of 100% cotton or other natural fiber. However, this option places the responsibility of choosing compliant clothing squarely on the employee. And, it will require additional “policing” on your behalf.
In our opinion, the most comprehensive approach is for the employer to specify and issue the appropriate FR base layers to be worn under the company’s FR uniforms. By doing so, not only are you taking the choice of undergarments out of the hands of your employees, and the questions of whether or not they have the right fiber content against their skin out of the equation. You will also be providing a second layer of FR protection should they inadvertently leave a shirt unbuttoned or untucked in a moment of complacency. (A layer that, believe it or not, can also provide greater comfort; most FR undergarments pull sweat away from the body to help keep workers cool and dry.)
In the case of protection against electric arc exposure, only FR layers can contribute to a composite ATPV rating, so issuing an FR base layer to be worn under an FR shirt may increase ATPV and possibly increase protection.
So, there you have it. Your base layer basics, compliments of the world’s #1 FR brand. Next time you’re evaluating your FR program, please keep these tips top of mind. And don’t let your undergarments become an oversight.
Shop our base layers.
Arming your crew with the appropriate FR gear is a feat in itself. Navigating the ever-changing sea of standards? Now that’s another beast entirely. Bulwark is here to help you choose the right FR program by ensuring you have a thorough grasp on the standards and what they mean for you—and your crew.
When the National Fire Protection Association (NFPA) introduced the term “Arc-Rated” or “AR” in its 2012 revision to NFPA 70E, it was a bit of a head-scratcher. The question on every safety manager’s mind was: what’s the difference between FR and AR? According to Bulwark’s Technical Training Manager, Derek Sang, the most basic and important thing to know when it comes to FR and AR is that all arc-rated clothing is flame resistant, but not all flame resistant clothing is arc-rated.
For a piece of clothing to be considered flame resistant, the fabric used to make the garment must withstand ignition and/or rapidly self-extinguish in order to protect the wearer from the dangers of flash fire, arc flash, molten metals and other hazards. In the event of a flash fire or arc flash, the FR PPE worn must resist catching fire, melting, and continuing to burn after the initial flash to act as a barrier between the wearer and the hazard.
The fabric used to create arc-rated clothing is subject to additional tests, above and beyond fabric labeled simply “FR.” Primarily, it is exposed to a series of arc flashes to determine how much energy the fabric is able to block before it would likely cause the wearer to obtain a 2nd degree burn, 50% of the time. The result of this test, expressed in calories, is known as the Arc Thermal Performance Value (ATPV).
Current standards for arc flash protection, detailed by NFPA 70E, state that all PPE clothing must also be flame resistant to qualify for an arc rating. In other words: all AR clothing is FR, but not all FR clothing is AR. This is because, based on the results of the series of tests outlined above, equipment rated FR may not always provide the adequate level of protection for workers who are at risk of encountering arc flashes. These employees—general industry electricians (70E)— must wear the appropriate level of AR clothing for the hazard, in order to reduce their risk of serious injury or death caused by an arc flash.
“How do I help my guys stay cool in the hot summer months?” That may be the #1 question we at Bulwark receive this time of year, every year. The world’s #1 FR brand is here to help guide you with some cold, hard facts.
1. Remember the 3 Rs: Rehydrate, Rest and Recognize
Rehydrate: Drink cool water often and before you feel thirsty.
Rest: Take breaks in shaded/air-conditioned areas: Especially when daytime temps are at their peak. Shorter, more frequent work/rest cycles are best.
Recognize: Learn to recognize the symptoms of heat-related illness in yourself and others; and report concerns immediately.
2. NEVER Cheat In The Heat
Keep shirts buttoned, sleeves rolled down, and tucked in. FR clothing can only protect you if worn properly.
3. The Right Base Layers Boost Comfort
Wicking base layers move perspiration from the skin outward, to allow for faster evaporation, and constant comfort.
An FR base layer adds protection and might even allow for the use of a lighter weight shirt without sacrificing ATPV/ Protection.
ALWAYS select a base layer that is flame resistant or at least 100% cotton
AR, FR, ATPV, OSHA. The list goes on and on. If there’s one thing that’s true about FR safety, it’s that there are a lot of terms to memorize. It’s not always easy to keep the various words and acronyms straight, but when it comes to building and implementing an effective safety program, knowing your FR vocabulary is important. Here, our FR experts have compiled the most important of those terms in a handy alphabetized glossary so you can create a culture of compliance.
An arc flash is a type of electrical explosion where temperatures can reach or exceed 35,000 °F. The Arc Flash hazard affects all who work in and around energized electrical equipment. This can include general industry electricians, maintenance workers and operators, as well as our electric utilities, including transmission, distribution, generation and metering.
Arc-Rated (AR) Protective Clothing
Arc-rated protective clothing protects from arc flash and electric arc hazards. AR garments are measured in cal/cm². The total AR clothing system must meet or exceed required arc protection levels. Remember, all AR is FR, but not all FR is AR.
Breakopen is the formation of holes in the fabric during arc rating testing. This is the point of failure of FR protective garments.
Energy Break-Open Threshold is an alternative measure to ATPV when that measure cannot be used due to breakopen.
A rapid moving flame front that can be caused by a diffuse fuel, such as dust, gas, or the vapors of an ignitable liquid, without the production of damaging pressure. Flash fire is the primary hazard in the Oil & Gas industry, which includes exploration, drilling, field services and refining.
Hazard Risk Assessment
The first step in the creation of any PPE program is the Hazard Assessment. Federal regulations require employers to assess the workplace to determine if hazards that require the use of personal protective equipment are present or are likely to be present. These include impacts, combustible dust, fire/heat, and chemical hazards, among others.
HRC (Hazard Risk Category)
Hazard risk categories are defined by NFPA® 70E and assigned based on risk associated with electrical safety and arc flash. HRC levels determine the appropriate ATPV of flame-resistant clothing for a given task.
Replaces HRC in 2015 edition of NFPA 70E, the “0” category was eliminated in NFPA 70E 2015. The minimum ATPV’s for PPE Category 1 through 4 are the same as they were for HRC, and the new PPE table only specifies PPE for work within the arc flash boundary.
HRC 2 rated garments have an arc rating between 8 cal/cm² and 25 cal/cm² and are often referred to as “daily wear.”
HRC 3 rated garments have an arc rating between 25 cal/cm² and 40 cal/cm².
HRC 4 rated garments have an arc rating equal or greater than 40 cal/cm². These high ratings are achieved with a layered FR system. Download our FR Layering Fact Sheet to learn the do’s and don’ts of layering for FR.
Inherently Flame Resistant
Inherently flame resistant fabrics are engineered to be flame-resistant at the fiber level, and do not require any additional finishing.
The National Fire Protection Association is an agency whose task it is to promote and improve fire protection and prevention. They publish National Fire Codes.
Refers to NFPA’s “Standard on Flame Resistant Garments for Protection of Industrial Personnel Against Flash Fire.” NFPA® 2112 is the “go-to” industry consensus standard that addresses flash fire. It defines the testing methods and performance requirements for flame-resistant fabrics for this hazard.
The “Standard for Electrical Safety in the Workplace,” NFPA® 70E is meant to protect those working around potential arc flash hazards. Note that NFPA® 70E applies only to general industry electrical safety, not to electric utility workers.
Founded by the Occupational Safety & Health Act of 1970, The Occupational Safety and Health Administration’s (OSHA) mission is to “assure safe and healthful working conditions for working men and women by setting and enforcing standards and by providing training, outreach, education and assistance.” Their general duty clause ensures a safe workplace for all employees and is the basis for all industry consensus standards. OSHA determines regulations and standards related to personal protective equipment.
The regulation states that power utilities make reasonable estimates of the incident heat energy to which their employee would be exposed, and that employees exposed to hazards from electric arcs wear AR clothing and other protective equipment with an arc rating greater than or equal to the estimated heat energy.
Founded in 1918, The American National Standards Institute coordinates and develops voluntary standards for products, services, and systems. The organization’s goals include performance consistency and product safety. It is the U.S. member body to ISO and IEC.
PPE (Personal Protective Equipment)
Personal protective equipment is specialized safety gear worn by an employee for protection against a hazard. Flame resistant/arc rated garments are a form of personal protective clothing worn against thermal hazards.
Moisture wicking fabrics pull moisture (sweat) away from the body and dry quickly, keeping the wearer cooler, dryer, and more comfortable. Bulwark iQ Series® FR Comfort Knits and Wovens are among the best moisture wicking FR garments available.
Breathability refers to how well a fabric allows air to be transmitted through the material. The more air that passes through, the cooler the wearer stays. Bulwark iQ Series® Endurance Collection is the first of its kind to offer high level FR protection in a material that is extremely breathable and durable.
Just like all of us here at Bulwark FR, Alice Stoll (1917–2014) was committed to taking FR to the highest degree.
That’s because Stoll’s research in the 1960’s led to the Stoll Curve, which is what FR experts use to determine what PPE is needed to reduce burn injuries.
You’re probably thinking, how did Stoll know at what conditions did things get too hot to handle? The answer: burn research. And it involved the forearms of sailors!
When she worked in the United States Navy Reserves, Stoll teamed up with another researcher named Maria Chianta to study the reaction of human skin to thermal energy/heat.
She conducted further research on the skin of pigs and rats—not sailors, thankfully.
The big takeaway from Stoll’s research was understanding the amount of heat or thermal energy that results in a 2nd degree burn on human skin. Alice Stoll’s contribution to FR apparel with this research is a crucial part of the thermal testing used to evaluate the ability of a fabric to protect against a variety of workplace hazards like flash fire, electric arc, molten metal splash and others. It’s also important to note that the Stoll Curve represents a relationship between time and energy. As we measure those relationships, we can determine Arc Thermal Performance Value (ATPV) ratings, and Breakopen Threshold Energy (EBT) ratings as well as predict the time to 2nd degree burn injury through FR fabrics.
Stoll received a number of awards including the Achievement Award of the Society of Women Engineers in 1969. The Bulwark team is proud to celebrate Alice Stoll, who had an important role in advancing FR technology.
When it comes to FR, the answer is: more than you might think. Even after assessing hazard risks and selecting the appropriate FR clothing, it also falls on the employer to ensure that each garment truly matches the hazard it’s designed to protect against. That’s why it’s especially important to identify proper labeling on the part of the manufacturer as an indicator that the garment is, indeed, fully compliant.
Read on to learn what to look for on your FR labels.
NFPA® and ASTM labeling requirements are strict, but not everyone follows the rules. Fraudulently labeled FR garments can often be identified by their violation of the standards. According to ASTM F1506 6.3, FR garments must be labeled with the following information:
6.3.1 Meets requirements of Performance Specification F1506
6.3.2 Manufacturer’s Name
6.3.3 Fabric Identifier
6.3.4 Garment Tracking and Identification Code
6.3.5 Size and other associated standard labeling
6.3.6 Care instructions and fiber content
6.3.7 Arc rating (ATPV) or arc rating (Ebt)
18.104.22.168 When garments are made with a different number of fabric layers in different areas of the garment, the arc rating for each area shall be designated. Pockets, trim, closures, seams, labels, and heraldry shall not be considered as extra layers.
That’s a lot of label, but it shows specific compliance, as opposed to labels that are misleading or omit critical information.
NFPA 2112, Chapter 4 provides clear requirements for shirts, pants, coveralls and outerwear. In addition to bearing the mark of the 3rd party certifier, the following words and the edition of the standard must appear on the label of a certified garment:
“This garment meets the requirements of NFPA 2112, Standard on Flame-Resistant Garments for the Protection of Industrial Personnel against Flash Fire, 2012 Edition. NFPA 2113 requires upper and lower body coverage.”
Beware of subtle changes in wording on the label that claim to meet a portion of the standard, but do not meet all requirements. For example, the following language does not meet the requirements of NFPA 2112:
“This garment meets the performance requirements of NFPA 70E-2009, ASTM F1506-02ae1, NFPA 2112-2007.”
There’s one more way to be sure your FR gear is fully compliant: Visit the UL website, where you can query to ensure that the garment has, in fact, been certified by UL.
While it may seem nitpicky, these standards for FR labeling are very important. They are designed to protect the FR provider and FR wearer from purchasing and wearing fraudulent FR garments, which do not meet the minimum requirements of FR safety.
Make a habit of reading your labels. Because when it comes to protecting yourself and your crew from the hazards associated with the job, you can never be too careful.