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Firefighter turnout gear, heat protection suits and protective suits for welders act as vital insurance for the life and safety of their users. To ensure protection, Personal Protective Equipment (PPE) manufacturers and users must adhere to relevant legal regulations and testing requirements as well as numerous functional requirements. Hohenstein, a global leader in textile testing and research, has long been concerned with quality standards for fire and heat resistant protective clothing, including test parameters and legal requirements, as well as optimum product performance and high wear comfort.
Depending on the hazard potential, the European market distinguishes between three categories of PPE:
The basis for developing PPE is always a hazard analysis. This involves investigating and evaluating the probability of occurrence of hazardous situations in relation to the severity of possible effects to determine the level of protection required. For example, when assessing the hazard situation for firefighters – the wide range of operations have different hazards, making it difficult to describe requirements precisely. In Europe, protective clothing for firefighters must
always have an EC type examination certificate from an approved notified body (see below). Since this is category 3 (highest protection level) protective clothing, annual monitoring is required. The manufacturer usually implements an appropriate quality assurance system. The sale, marketing and use of personal protective equipment in the European market is subject to mandatory CE marking and the conditions attached to it.
European law requires that PPE certification be conducted by a notified body. As an accredited testing laboratory and notified body (Notified Body 0555) for personal protective equipment in accordance with the EU Regulation (EU 2016/425), Hohenstein guarantees the safety and conformity of PPE.
The advantages for customers are obvious:
If a manufacturer makes any changes to PPE that has already been certified, the notified body responsible for certification must be informed. The notified body then decides whether the protection performance will still be effective after the changes or whether the product no longer meets the health and safety requirements.
According to the European manufacturing and testing description, firefighters’ protective clothing can be constructed in different ways. Usually the structure consists of an upper fabric, a moisture barrier, an element for thermal insulation and an inner lining. Textile insulation layers can be separate or directly connected to the wetness barrier, as long as the inside is always formed by a lining material. Thermal insulation can also be provided by spacer technology, i.e., spacers that ensure air flow. Spacers must be made of flame-retardant materials.
Heat protective clothing for industrial workers protects against brief contact with flames and/or radiant heat, large molten metal splashes or combinations thereof. Heat and fire protection clothing consists of special flame retardant or
non-flammable fibres, such as glass, aramids or polyimides or of flameretardant cotton or wool fabrics. An aluminum reflective coating considerably reduces the effect of heat radiation.
Hohenstein uses various test methods to examine the protective effect of textiles, seams and clothing against flames and fire. Fire fighter gear is designed to protect the wearer during both firefighting and related activities, such as rescue work or in disaster situations. The most important safety-relevant requirement for firefighter protective clothing is limited flame spread.
This means that, during testing, both the outside and the inside of the material structure are exposed to flame.
In addition, the entire clothing system can be flame-treated on a dummy – without undergarments and without firefighting accessories. The dummy is exposed to an average exposure temperature of 800 to 1,000 degrees Celsius for eight seconds. The experts then determine the extent to which a wearer can expect second- and thirddegree burns.
Weak points in the construction of the protective clothing must be revealed. Expert examination considers things like missing or insufficient insulation or incompatible material layers. If, for example, one of the layers shrinks more than the others during flame treatment, the protective effect is lost.
The importance of proper construction becomes very clear in the case of jackets. Normally, a jacket of between 10 and 12 centimetres is shortened in the rear back area when exposed to flame. The shrinkage is significantly higher if the layers are not properly constructed. If one of the layers shrinks too strongly, it pulls all the layers up the wearer’s back. The user then lacks the necessary insulation intended by the protective jacket. Shrinking reflective stripes to improve visibility can also cause protective clothing to be pulled up or pulled too tightly against the body. All of these elements must be considered in the testing plan.
Another requirement for firefighter protective clothing is thermal insulation, or protection against heat transfer when exposed to flames or radiation. To achieve this, experts apply a gas burner to the outside of a material sample with an energy quantity (heat flux density) of 80 watts per square metre. The temperature increase and the time required are measured on the side facing away from the flames. The heat transfer index (HTI) is determined from this data. This index is an indicator of the relative protection against heat exposure. HTI 12 corresponds to a temperature increase up to the pain threshold on the skin. HTI 24 is equivalent to a temperature increase that can lead to second-degree burns of human skin.
EU certification of protective clothing for firefighters requires that it takes at least 13 seconds of flame exposure to reach the limit value of a theoretical seconddegree burn on the skin. What does this mean in practice? For the emergency services, the HTI 24 – HTI 12 index indicates the period of time between the wearer’s reaction to pain and when second-degree burns occur.
The same principle applies to protection against heat radiation. For this purpose, the test procedure involves exposing the protective clothing to heat radiation of 40 kilowatts per square meter. On the side facing away from the sources of radiation, the temperature increase is determined up to RHTI 12, an empirical limit that approximately corresponds to the pain threshold of human skin, and up to RHTI 24, where second-degree burns are possible.
Waterproofness is divided into two levels for firefighters’ protective clothing: with and without a wetness barrier membrane. The test is performed on the surface and in the seam area. Protective clothing without a moisture barrier is not considered protective against water, chemicals or other liquids.
Moisture barriers protect against more than just water. Leak tests of the moisture barrier also include contact with fuels, oil and foaming agents – after heat treatment (at 180 degrees Celsius). Leak tests are also conducted with after treatment solvents and other typical fire department application scenarios.
The water-repellent properties of the outer fabric are achieved by a carbon resin finish. Such finishes do not hold up during use or mechanical cleaning processes and must be renewed during reprocessing.
“if one of the layers shrinks too strongly, it pulls all the layers up the wearer’s back. The user then lacks the necessary insulation intended by the protective jacket”
The outer fabric is tested for resistance to penetration of liquid chemicals. For this purpose, the test liquid is applied with a fine jet to the surface of a sample arranged in an inclined channel. At least 80 percent of the applied chemicals should arrive at the end of the gutter. Ideally, no liquid should penetrate the innermost layer of the sample, which corresponds to the structure of the protective clothing. However, fabrics and other textile materials are generally not as effective as moisture barriers. If there is an effective moisture barrier behind the outer fabric, the liquid does not penetrate as deep into the garment. It can therefore be assumed that a moisture barrier can provide protection against moisture and liquid soiling such as common chemicals, fire water, dust, fuel and oil. Thus, the tests for resistance to the penetration of liquid chemicals are also carried out on the moisture barrier and then the waterproofness is tested in a water pressure test.
“when processing PPE, the primary objective is to ensure lasting quality and maintain protective functionality for the users”
Emergency responders must perform physically heavy and stressful work while wearing the protective clothing – under the influence of high temperatures. In these conditions, humans produce sweat. Water vapour produced during sweating must be transported from the inside to the outside of the garment as quickly and directly as possible. A high resistance to the passage of water vapour – or low breathability – increases the risk of skin injuries due to scalding and reduces the wearer’s physical resilience. Impeded sweat vapour removal causes reduced cooling – and possibly overheating (hyperthermia) – of the body, which can cause considerable physical strain and even fatality.
With such serious implications, thermal insulation must remain intact and unobstructed during all relevant activities, ranges and sequences of motion and environments. Hohenstein checks that there is sufficient freedom of movement and body coverage during all movement sequences of the intended application. Trained test persons are selected according to the size and finished measurement tables of the manufacturers. Ideally, the protective clothing should be individually adapted to each wearer.
When processing PPE, the primary objective is to ensure lasting quality and maintain protective functionality for the users. The PPE manufacturer is required to specify how the textile products must be reprocessed to guarantee protective performance over the entire service life. In general, protective clothing should not be washed in the normal household laundry because the protective function cannot be checked. Whether processing protective clothing in the company’s own laundry or textile service companies, the washing instructions supplied by the manufacturer must be followed. Due to the complexity of legal requirements and company occupational health and safety guidelines, an increasing proportion of textile PPE is leased.
Above all, personal protective equipment must provide safety. However, other aspects also contribute to a successful market launch and the reliability of a product: here a balance of function, design and sustainability is essential.
Dr Jan Beringer
Dr Jan Beringer, Senior Scientific Expert, Hohenstein With around 1,000 employees in more than 40 branches and contact offices worldwide, Hohenstein is an internationallyoriented testing services provider and research partner in the textile industry. You can find more information about Hohenstein on www.hohenstein.com/PPE.
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