Flame Resistant and inherent fabrics Frequently Asked Questions

After flame time (s)

Length of time for which an after flame persists under specified conditions. After flame time is one of 5 key values which are measured by mean of Vertical burn test (aka ASTM D6413 or ISO 15025). Flame retardant fabric should not have After flame more than 2 seconds. So, FR-fabric might have a little After flame, but less than 2s.


Time of glowing after flame has extinguished itself when testing a flame retardant fabric. Persistence of glowing after cessation of flaming or if no flaming occurs, after the ignition source have been removed. It must be less than 2s according to ASTM D6413.

Arc flash

An arc flash is a type of electric explosion from a voltage breakdown of the resistance of air. Arc flash temperatures can reach or exceed 35,000°F. An arc flash hazard may exist when energized electrical conductors or circuit parts are exposed. The bright flash from the event can result in temporary or permanent blindness. All of these will most likely result in equipment damage as well as personnel injury, and possibly death.

Flame retardant clothing, the primary purpose is to resist ignition (as tested by ASTM D-6413, also known as Vertical Flame Test). If flammable clothing is ignited by an arc flash, flash fire, molten metal, etc, the hazard to the wearer instantly becomes much greater, because a clothing fire will last much longer than the initial hazard, will typically burn the victim over a much larger body surface area and more deeply, and is more likely to result in airway and lung damage.

Arc-rated protective clothing

Arc-rated flame retardant protective clothing protects from arc flash and electric arc hazards. Arc-rated garments are measured in cal/cm². It is required to determine necessary arc protection levels and to insure that proper personal protective equipment is worn.

ATPV (Arc Thermal Protective Value)

It establishes the maximum performance capability for a specific garment or fabric. ATPV is what arc-rated protection measures.
Flame retardant fabrics of XM FireLine Etna has ATPV – 16 cal/cm2, Gefest-420 has ATPV – 20 /cm2.


Breathability refers to how well a workwear fabric allows moisture vapor to be transmitted through the material. It also makes flame retardant fabric comfortable to wear and allow to use it in different climate conditions.

Flame Retardants

Flame retardants are a key component in protection and reducing harmful impact of fires on workers. Treating workwear fabrics with flame retardants allow you prevent fires from starting, limit the spread of fire and minimize fire damage.
The term “flame retardant” refers to a function, not a family of chemicals. A variety of flame retardants is necessary because materials that need to be made fire-resistant are very different in their physical nature and chemical composition, so they behave differently during combustion. Flame retardants work to stop or delay fire, but, depending on their chemical makeup, they interact at different stages of the fire cycle. 
Treated fabrics used fo flame retardant workwear manufacturing are cotton or cotton-blend fabrics that are treated with chemicals that form a permanent bond with the fabric that cannot be washed out when the recommended laundering instructions are followed. The chemical treatment changes the molecular structure of the fabric.

HRC (Hazard Risk Category)

Hazard risk categories are defined by NFPA70E standard and assigned based on risk associated with electrical safety and arc flash. HRC levels determine the appropriate ATPV of flame resistant clothing.
HRC 0 – FR clothing is not required but the clothing must be non-melting or untreated natural fibers. PPE includes safety glasses or goggles, hearing protection and leather gloves.
HRC 1 – FR clothing with a minimum arc rating of 4 cal/cm² (long sleeve shirt & pants or coverall, and arc rated face shield or hood). PPE includes hard hat, safety glasses or goggles, hearing protection, leather gloves and leather work shoes optional.
HRC 2 – FR clothing with a minimum arc rating of 8 cal/cm² (long sleeve shirt & pants or coverall, and arc rated face shield or hood). PPE includes hard hat, safety glasses or goggles, hearing protection, leather gloves and leather work shoes optional.
HRC 3 – FR clothing with a minimum arc rating of 25 cal/cm² (either single layer shirt and pant, coverall or a multilayer flash suit system and arc rated flash suit hood). PPE includes hard hat, FR hard hat liner, safety glasses or goggles, hearing protection, arc rated gloves and leather work shoes.
HRC 4 – FR clothing with a minimum arc rating of 40 cal/cm² (either single layer shirt and pant, coverall or multilayer flash suit system and arc rated flash suit hood). PPE includes hard hat, safety glasses or goggles, hearing protection, leather gloves and leather work shoes.

Inherent fabric

Inherent fabrics are made with fibers that are designed to be flame resistant. Flame resistance is part of the fibers and is a permanent characteristic of the fabric.
Inherently flame resistant fabrics, flame resistance is an essential characteristic of the fiber from the textile is made. Because the actual structure of the fiber itself is not flammable, the protection it affords is permanent-it can never be worn away or washed out.
When exposed to flame, inherently flame resistant fiber swells and becomes thicker, forming protective barrier between the heat source and the skin. This protective barrier stays supple until it cools, giving the wearer vital extra seconds of protection to escape.
Fabrics made with inherently flame resistant fibers, chemically treated flame resistant fabrics may have their flame resistant properties diminished or removed completely depending on how these fabrics are laundered and/or which chemicals they are exposed to in the work environment.
The flame resistant properties of inherent fabrics cannot be washed out or worn away, period. This means the flame resistant properties of apparel made of inherent fibers cannot be compromised. It is crucial for the wearer to know the flame resistant protection is always there. Fire-resistant properties are built directly into the molecular structure of the fibers, making them flame resistant from the inside out.

Life of the Garment

Flame resistant garments are generally made from either flame retardant of inherent materials (including meta-aramids and para-aramids). FR treatments can Wash Out over time or can be mechanically damaged, that shorting the life of the garment. Because many garments are often laundered under industrial wash conditions, they must be capable of withstanding a number of such industrial launderings in order to have an acceptable useful life. It is generally considered by the purchasers of these garments that the garments must last through a minimum of 50 industrial launderings. However laundry care instructions must be strictly followed, any improper laundering will drastically shorten the life of the garment. 
You must remember the FR protective treatment can wash out over time, diminishing the flame resistant quality of the garment, yet the garment looks good. 
Flame retardant garments can be repaired using the same type of FR materials used in the original cloth such as the fabric and thread. Use of non FR thread or fabrics will affect the performance of the garment as that area where the incorrect material is used will not provide adequate protection. It is suggested to contact the manufacturer for replacement materials to repair your FR garments. Each company should select the product that best meets its overall needs, assuming that the product provides the required FR protection. 
The wear life of FR clothing is very dependent on the type of fabric used and the quality of the garment construction. Some types of garments can last more than 5 years, while other types may last 9 to 18 months.


The National Fire Prevention Association (NFPA) is a global, non-profit organization that promotes safety standards, education, training, and advocacy on fire and electrical-related hazards.

The widely identifiable NFPA diamond is a type of safety sign that emergency responders use to quickly identify dangers posed by hazardous materials.

The sign, with the meaning of its colors and numbers, is part of a larger standard maintained by the NFPA.

NFPA standards regulate the quality and norm for gas and oil industry workers, welders, electricans, firefighter work wear, to provide the high level of protection.


The Occupational Safety and Health Administration, more commonly known by its acronym OSHA, is responsible for protecting worker health and safety in the United States.

OSHA coverage extends to most, but not all, private sector employers and their workers. OSHA rules cover numerous industry workplaces from construction to maritime to agriculture. The agency also covers some public sector employers and their workers, usually through state OSHA agencies that regulate public sector employers.

To comply with OSHA requirements, employers must take a number of specific actions; those include inspecting the workplace for potential hazards, eliminating or minimizing hazards, keeping records of workplace injuries and illness, training employees to recognize safety and health hazards, and educating employees on precautions to prevent accidents. OSHA also requires employees to follow rules, such as complying with all applicable OSHA standards, following OSHA safety regulations, wearing required protective equipment, reporting hazardous conditions, and reporting job-related injuries and illnesses. OSHA also protects employees by guaranteeing a host of rights.

Vertical Flame test

This test method measures the vertical flame resistance of textiles in general, but does not describe or evaluate the fire risk or fire hazard of those materials. Samples cut from fabric to be tested are mounted in a frame that hangs vertically from inside the flame chamber.

A controlled flame is exposed to the sample for a specified period of time. After-flame time, the length of time the material continues to burn after removal of the burner, and after-glow time, the length of time the material glows after the flame extinguishes, are both recorded. Finally, the specimen is torn by use of weights and the char length, the distance from the edge of the fabric that was exposed to the flame to the end of the area affected by the flame, is measured.

What should be worn with FR clothing?

Every type of Flame Retardant work wear is designed to protect employees against different hazards. To provide the additional level of comfort you can wear 100% cotton fabrics under Flame Retardant clothing. It will provides layering and air gaps that would add to the thermal insulation.

The underwear can add to the comfort as it is made to be next to the skin and is typically softer to the touch. Cotton materials have the ability to absorb perspiration better than FR fabrics. This last benefit can be either a pus or a minus depending on whether the fabric dries quickly or stays wet, but that’s another topic all together.

It is not recommended to wear fabrics that may melt when exposed to a flame source such as nylon, polyester, polypropylene or spandex under or along with your flame resistant protective clothing.