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EN 443: 2008
Impact / Shock Absorption
Firefighters helmet include impact tests similar to those specified in EN 397 (albeit with a greater energy level) plus additional tests unique to helmets intended for firefighters. The area around the crown of the helmet is impacted using a falling striker method, similar to that required by EN 397. A 5 kg hemispherical striker is dropped onto the helmet mounted on a suitable sized rigid headform from a height sufficient to generate an impact energy of 123 J (approximately 2.5 metres), with a maximum allowed transmitted force of 15 kN. The rest of the protective area of the helmet is also subject to an impact from small projectiles – a steel ball of diameter 6 mm is fired at the helmet at a speed of at least 120 m/s (268 mph), with no penetration of the ball or helmet material through the helmet to contact the headform underneath allowed. Testing is carried out following conditioning to UV light, thermal shock (low temperature immediately followed by high temperature, then water immersion, then high temperature again), contact with solvent, and either high temperature (50°C), low temperature (-10°C, -20°C, -30°C or -40°C) or water immersion.
Firefighter helmets are subject to a penetration test using a blade-shaped striker. The striker (pointed blade, of 6 mm thickness, 0.25 mm point width, 1 kg mass) is dropped on the helmet shell from a height of 2.5 m (crown impacts) or 2 m (off-crown) impacts, with no penetration of the blade through the helmet allowed. Testing is carried out following conditioning to UV light, thermal shock (low temperature immediately followed by high temperature, then water immersion, then high temperature again), contact with solvent, and either high temperature (50°C), low temperature (-10°C, -20°C, -30°C or -40°C) or water immersion.
Most specifications for protective helmets include a number of requirements for the design of a helmet in addition to the specific performance requirements. These typically encompass the area of coverage provided by the helmet, as well as the field of vision afforded to the user when worn. They can also cover a number of ergonomics and safety-based requirements, such as clearance between the head and the shell of the helmet (particularly in the case of industrial helmets).
Helmets can only protect the head when they are being worn and therefore the means for retaining the helmet on the user’s head requires as much attention as the rest of the head protection, and so is subject to a series of tests. The specific test carried out is dependent on the type of helmet, but two main tests are carried out:
Retention system strength: The retention system (in particular, the chin strap) is subjected to a force, applied either statically or dynamically, to ensure the strap is unlikely to fail at the point where it is most necessary. In the case of industrial helmets, it is however desirable that the chin strap will not cause a strangulation hazard, and so cannot be too strong, and therefore straps need to include a break-away element at the anchorages, intended to fail within a specific load range. Typically, the helmet, including chin strap, is fitted to a suitably-sized headform, with the chin strap either fitted to an artificial chin (consisting of two rollers mounted on a frame), where the headform remains static, or to the chin of the headform itself, where the headform is used to dynamically apply the force. The chin strap is then subjected to either a static force (where the artificial chin is slowly loaded until failure) or a dynamic (shock) load, applied using a falling mass, and the amount of stretch in the chin strap is measured.
Retention system effectiveness: Helmets are subjected to a shock load, applied to the rear or front of the helmet in an attempt to pull the helmet off the headform. This is intended to consider the risk of the helmet catching on an obstacle and being unintentionally pulled off the user’s head. The test load (applied using a 10 kg falling mass) is applied, via a system of pulleys, to the rear of the helmet when mounted on a suitable headform, with the direction of loading following a direction approximately 45° from the horizontal towards the front of the headform (this is occasionally repeated on the front of the helmet). In order to meet the requirements of most protective helmet standards, the helmet must remain on the headform.