Our How it's Tested series explores safety standards and test methods for AR / FR garments and PPE. With Scott Margolin, Vice President of Technical as our guide, we examine many of the major tests to understand what they measure, how they measure it, and what that means to someone like you who is specifying or wearing the garment. Whether you are a seasoned professional or just starting out, explore all episodes in this series to make sure you are up to date on the latest information.
We’re breaking down the various tests in NFPA 2112 for flash fire protection. Now that we’ve taken a closer look at “the Manikin Test” (ASTM F1930) – the most well-known of the tests, we’re turning our attention to the other three main fabric tests in the standard.
Scott Margolin, Vice President of Technical, walks us through NFPA 2112’s pass/fail criteria for Vertical Flame (ASTM D6413), Heat Transfer Performance (ASTM F2700), and Thermal Shrinkage (ASTM F2894):
NFPA 2112 provides strict pass/fail criteria on each of these three (3) fabric tests to help identify flame resistant fabrics that meet the minimum performance properties necessary to be worn for flash fire protection.
1) Vertical Flame Test, ASTM D6413
NFPA 2112 requires a char length of 4” or less on the Vertical Flame Test (ASTM D6413), on a sample that has been laundered 100 times. Check out Episode 2 for a closer look at the vertical flame test.
Remember: ASTM provides test methods, but the pass/fail criteria applied to the test methods are most often found in other standards – in this case, NFPA 2112. Different standards (like ASTM F1506 on the arc flash side) can use the same test method, but have different requirements to pass.
2) Heat Transfer Performance (HTP), ASTM F2700
The HTP test measures a fabric’s ability to insulate the wearer from a second-degree burn.
To do this, it exposes a small piece of fabric to a steady heat source from below, while a thermocouple on top of the fabric measures the heat that passes through.
- It is conducted both with and without a spacer to mimic whether or not the fabric is touching your skin.
- The test is concluded when the thermocouple measures heat sufficient to achieve a second-degree burn through the fabric, and can predict the time it takes to achieve a second-degree burn.
To pass NFPA 2112, a fabric must achieve a 3+ calorie rating when in contact, or 6+ calorie rating when spaced, by the time the sensor records a temperature which exceeds those causing second-degree burn.
3) The Oven Test (also known as the Thermal Shrinkage Test), ASTM F2894
This test is actually used to evaluate fabrics with respect to two requirements in NFPA 2112:
- Thermal Shrinkage: In this test, a 15” square sample is washed three times then placed into a hot air-circulating oven set to 500°F, for five (5) minutes. To pass, the fabric may shrink no more than 10% during the test.
- Heat Resistance: In this test, a 6” square fabric sample is used in the same apparatus to make sure it doesn’t ignite, melt, drip, or separate as a result of the heat exposure. This is used to evaluate materials like insulation and other components of a garment, which aren’t to pass the shrinkage test.
Each of these tests serves an important role in measuring a fabric’s response to heat under controlled conditions.
By using these tests together and in combination with several other tests, NFPA 2112 provides the backbone needed to ensure a fabric or garment combines all the features necessary to effectively protect a worker in the event of a flash fire.
In our next post, we’ll examine the other tests in NFPA 2112 that serve a lesser-known but important role in identifying flame resistant fabrics that can be worn for flash fire protection.