Fireman Equipment Questions & Answers
What is TPP?
Answer: TPP stands for Thermal Protective Performance. The TPP rating of a fabric or composite refers to its thermal insulation characteristics when protecting the wearer from fire. TPP is measured using a combination of flame and radiant heat sources with a heat flux of usually 84 kW/cm2 (2 cal/cm2-sec). The flame is impinged on the outer surface of a 10.5 by 10.5 cm area of the fabric or composite. The time required to reach the equivalent of a second-degree burn at the calorimeter on the other side of the sample is recorded. This time (in seconds), multiplied by the heat flux of the exposure, gives the TPP rating. The higher the TPP rating, the more protection a fabric or composite provides the wearer.
What is Thermal Damage Tolerance?
Answer: Thermal Damage Tolerance is a qualitative measure of the stability of a fabric after flame exposure. After a fabric is exposed to flame, does the material break open, form a hard char or remain flexible? Fabrics made of Nomex® fibre will form a flexible char when exposed to flame; upon cooling, the char will harden. Fabrics with high levels of Kevlar® fibre can remain flexible after flame exposure. However Kevlar® has higher heat transfer so that the heat is not absorbed by it – it goes through the fabric.
What is the difference between producer-coloured and piece-dyed fabrics?
Answer: Producer-coloured fibres are coloured during the fibre-making process, while piece-dyed fabrics are coloured after the fabric is woven together. Producer-coloured fibres generally have better colour stability to light and heat exposures. Piece-dyed products tend to come in a wider variety of shades.
Can DuPont perform tests in compliance with EN469 or EN ISO11612?
Answer: The European Technical Centre in Meyrin, Switzerland, is accredited for almost all the tests described in these norms.
Is the DuPont™ Thermo-Man® test simulating a real life scenario?
Answer: Thermo-Man® is one of the most advanced test methodologies for thermal protective garments, that can simulate scenarios that would probably only rarely occur to any firefighter. However it helps garment makers and weavers design better garments.
Is the DuPont™ Thermo-Man® an objective test?
Answer: Yes. DuPont has designed and developed the manikin test in order to help first the US government and then the PPE industry to better design garments. DuPont, a science company, has always followed the stricktest scientific rules of running the test. The DuPont™ Thermo-Man® can perform tests in compliance with EN-469:2005, clause 6.15 and is also able to perform tests in compliance with ISO-13506:2008, if required. ISO 13506 is an optional test within EN ISO 11612.
Why are there such big differences in the burn results of the different manikin tests?
Answer: Manikin tests results may vary due to several reasons. Some of the reasons can be: size of the garment (smaller sized garments are tighter and result in higher burn rate), using different burn result interpretation software, calibration and type of sensors, etc. At DuPont we work with customers to help them understand these test results.
Why does DuPont use a blend of Nomex® and other fibres in outershell fabrics?
Answer: When it comes to turn-out gear, manufacturers consciously construct outershells using Nomex®, a meta-aramid fibre, along with a lesser percentage of Kevlar®, a para-aramid fibre that helps provide additional tensile strength. It is important to know that where para-aramid content is dominant in the fabric, disadvantages such as higher heat transfer, lower durability, higher UV sensitivity, lower wash tolerance may arise, all of which lead to higher repair and replacement costs.
Why are there different fabrics and fibre blends used in outershells in different regions?
Answer: Across continents, different norms and measurement methods are used. These often reflect the local firefighting techniques and strategies, also taking into consideration the construction characteristics of buildings. In countries with wooden house structures, fires usually spread faster and firefighters may need to enter into the fire fast to save lives, which can require higher mechanical performance for the garment. In stone based buildings, fires are slower to spread, firefighters can develop alternative strategies to fight fire, therefore the firefighter garment needs are different. Garment makers, as well as the whole value chain, adapt to the local norms and needs, developing the materials that address the firefighters' needs.
What is the right fibre blend of Nomex® and Kevlar®?
Answer: It is important to know that where para-aramid content is dominant in the fabric, disadvantages such as higher heat transfer, lower durability, higher UV sensitivity, lower wash tolerance may arise, all of which lead to higher repair and replacement costs.
What is the role of the outershell fabric in preventing heat stress?
Answer: Outershell fabrics in multilayer garments have a dual role: in case of an outside-in effect of heat and flame, it is the first line of defense. At the same time, it has to offer high permeability so that it helps the membrane function, allowing for better air exchange and release of body heat. A good, lightweight outershell decreases the risk of heat stress.