NFPA 2112, Standard on Flame Resistant Clothing for Protection of Industrial Personnel Against Short Duration Thermal Exposures from Fire
What’s the purpose of this standard?
The purpose of NFPA 2112 is to evaluate PPE performance in terms of its ability to protect the wearer from a flash fire.
The biggest aspect of protecting a wearer is for clothing to simply not become fuel. In a flash fire exposure, garments that are not flame resistant can ignite and continue to burn long after the flash fire is over. Non-FR clothing not only doesn’t prevent injury, but it can additionally cause it.
The second aspect of protecting the wearer is thermally insulating them from the flash fire. In the same way that an oven mitt protects a hand from a hot pan, the garment protects the body from the brief, but very hot flash fire.
With these primary elements of protection in mind, we can discuss the specific fabric tests used in this standard and how they relate to protecting the wearer.
ASTM D6413, Standard Test Method for Flame Resistance of Textiles (Vertical Test)
This test method is used to compare fabrics’ responses to a standard flame exposure. The purpose for its use in this standard is to ensure that the fabric either self-extinguishes or does not ignite when exposed to a flame, and that it is not substantially compromised by the flame (for example, it does not fully burn as a way to “self-extinguish”).
In this test, a piece of fabric is cut and placed in a frame, then its lower edge is exposed to a standard flame source for 12 seconds. Once the flame source is removed, afterflame time is measured (any additional time it takes for the fabric to stop burning). Observations such as melting or dripping are made (fabrics cannot melt and drip). Lastly, the char length is measured – this is essentially comparing the damage done by the flame exposure and can be a useful means of comparing fabric performance.
Five specimens are tested in each direction (warp and filling). For this standard, the average afterflame time cannot exceed 2 seconds, and the maximum average char length is 100 mm in either direction. This test is performed before laundering, and after at least 100 cycles of washing and drying to ensure continued performance of the fabric.
NFPA 2112, par 8.4, Heat and Thermal Shrinkage Resistance Test
This test is essentially two tests in one. Three large squares of fabric are cut, measured and marked, then placed in a 260°C oven for 5 minutes to determine whether they melt or ignite, or if they shrink substantially in high heat. The maximum allowable shrinkage in any direction is 10%.
Although not particularly representative of a real-world thermal incident, this test helps weed out fabrics that are not thermally stable and could become hazardous to the wearer in a flash fire event.
NFPA 2112, par 8.2, Heat Transfer Performance (HTP) Test
(references ASTM F2700, Standard Test Method for Unsteady-State Heat Transfer Evaluation of Flame Resistant Materials for Clothing with Continuous Heating)
The purpose of the HTP test is to measure the amount of heat that is transferred through a fabric. To do this, the fabric being tested is placed between a heat source and a sensor. The heat source mimics temperature and heat types (radiant and direct flame) that are seen in flash fire incidents. The sensor is used to record the amount of heat absorbed and compare it to the Stoll curve, essentially telling us how long the fabric would protect skin before it would reach a second degree burn.
This test is performed with a spacer (to mimic the air gap present between the body and PPE) and without a spacer (contact test), both before laundering and after three cycles of washing and drying. The fabric must have an HTP of at least 6 cal/cm² for spaced tests, and at least 3 cal/cm² for contact tests.
ASTM F1930, Standard Test Method for Evaluation of Flame Resistant Clothing for Protection Against Fire Simulations Using an Instrumented Manikin
This test is a full-scale test involving a standard coverall (i.e. no pockets, striping or additional features) dressed on a full-sized manikin (over a base layer of cotton t-shirt and briefs), then lit up in a controlled flash fire simulation. The purpose of the test is to observe the fabric behavior in a simulated flash fire, and determine how well it protects the manikin’s “body” from the heat of the flash fire.
The manikin is instrumented with 100+ sensors that absorb heat in a manner similar to skin. As in the HTP test, the sensors are used to record the amount of heat absorbed through the fabric and compare it to the Stoll curve in order to predict the amount of burn injury that would occur in a 3 second flash fire.
The results are expressed as a percentage of the body area that would receive 2nd and 3rd degree burns based on the flash fire simulation. For NFPA 2112, up to 50% body burn is allowable. This is based on what is considered survivable for a healthy person. Origin FR strongly recommends examining test results before committing to any fabric. Our 7 and 9 oz coveralls have been tested and show 10.7% and 7.4% body burn respectively, which is almost exclusively comprised of the manikin head, which is exposed in these standard tests.
NFPA 2112 also has requirements for legibility (labels must be legible after 100 washes), thread (thread cannot melt or ignite at high temperatures), hardware (cannot melt at high temperatures; metal cannot be exposed to the skin on the inside of the garment), and certification (full third party certification is required to claim compliance to this standard).
This is an in-depth standard, and we at Origin FR are happy to walk you through any aspects of it and show you how our garments meet or exceed these requirements.