Selection of Head Protection and Eye and Face Protectors

Central Institute for Labour

Protection - National Research Institute

GENERAL RULE FOR SELECTION OF PERSONAL PROTECTIVE EQUIPMENT

The general rule for the selection of helmets, eye and face protection is the same as for all other types of personal protective equipment, except that eye protectors must take into account possible visual impairment of users. A summary of several methods described in the literature, which constitute the basis for the proper selection of personal protective equipment, may be proposed by the authors’ original, simple method of the CRS triangle (C - protective characteristics; R - hazards/risk occurring at the workplace; P - personal protective equipment whose characteristics correspond to the hazards and risks occurring in a given work environment), the diagram of which is presented in Figure 3.1.

In the diagram presented in Figure 3.1, the vertices of the base of the triangle are the characteristics of personal protective equipment and the hazards and risks occurring at the workplace. This means that for the proper selection of personal protective equipment, basic knowledge of the characteristics of the equipment and of the hazards and risks occurring in the work environment and the resulting risks is necessary.

Conducting a hazard analysis and risk assessment is the first step necessary to perform before proceeding with the selection procedure for personal protective equipment. Any further action is inappropriate without this stage. A detailed hazard analysis and a reliable assessment of the level of risk on its basis make it possible to draw up a list of characteristics that personal protective equipment must have in order for the materials used and the full design of the protective equipment to provide real

Personal protective equipment

protective equipment

FIGURE 3.1 A diagram illustrating the general principle of selection of personal protective equipment.

protection against the identified hazards, in accordance with the level of risk involved. While drawing up the list of characteristics of personal protective equipment, the individual requirements of the users and the fact that the equipment can be used together with another type of protection (compatibility) should also be considered.

SELECTION AND USAGE OF SAFETY HELMETS

The first fundamental step in the selection of protective helmets is the assessment of the hazards and environmental conditions occurring at a given workplace. The most important phenomena and factors that need to be identified are:

  • • The occurrence of falling objects
  • • The occurrence of stationary objects that pose a risk to hit them with the head
  • • The action of horizontal forces threatening to squeeze the head transversely
  • • Atmospheric factors such as negative and positive temperatures, humidity, direct sunlight
  • • Hot factors such as molten metal splashes, open flame, infrared radiation, etc.
  • • Aggressive chemicals
  • • Contact with live metal parts
  • • Explosive atmosphere
  • • UV radiation
  • • Use with other types of personal protective equipment.

The occurrence of mechanical hazards, such as impacts by falling objects and impacts upon dangerous elements of the workplace, determine the type of helmet to be used. Bump caps may be considered if there is no danger from falling objects, only the possibility of superficial injury to the scalp when hitting hard objects. This provides sufficient protection while maintaining comfort. In the event of a risk of impact by falling objects, it is necessary to use at least helmets meeting the requirements of EN 397:2012+Al:2012 [CEN 2012a], ANSI/ISEA Z89.1-2014 [ANSI/ISEA 2014], ISO 3873 1st Edition 1977 [ISO 1977] or AS/NZS 1801:1997 [AS/NZS 1997]. This will also protect the user’s head from being hit by stationary objects and structures. If there is a risk of impact on objects with high kinetic energy at the workplace, and in addition the impact can be directed not only to the top, but also to the front, back and sides of the head, it is necessary to use high performance industrial helmets, e.g. meeting the requirements of EN 14052:2012+Al:2012 [CEN 2012b]. The advisability of such a choice is confirmed by the results of tests presented in the articles Baszczyriski [2014a] and Korycki [2002], where the influence of the position of the impact point on the helmet shell on its shock-absorbing properties is presented. Typical safety helmets meeting the requirements of EN 397:2012+A 1:2012 [CEN 2012a] were tested by measuring the maximum force from the impact of a striker on a headform with the helmet on. It was found that during impacts of a striker with the same kinetic energy, the force applied to the headform with respect to the top point of the helmet shell was about 3 to 5 times smaller than with respect to points located near the lower edge of the shell. This means that helmets of this design are not effective protection against side impacts. The solution to this issue is the use of helmets equipped with protective padding, located between the harness and the shell. In such a helmet design, the shock of the impact energy, as the impact moves to the edge of the shell, is gradually absorbed by the protective padding [Forero Rueda 2009; Gilchrist 1989; Shuaeib 2007].

In industrial practice, there are workstations where there is a risk of lateral deformation, e.g. when carrying loads. In such a situation it is necessary to use a helmet with proven resistance to lateral deformation.

If the work performed at a given workstation poses a risk of the helmet falling off the head due to the employee’s position, the helmet should be designed in such a way that the headband fits exactly to the occipital part of the head and is equipped with a chin strap. This problem particularly concerns the simultaneous use of helmets with personal fall protection equipment. In such a situation, during the fall arrest accompanied by swinging motion and collision with the workplace structure, the fact of fastening the helmet under the chin (and thus preventing it from slipping off the head) may determine the health and life of the worker [Baszczyriski 2018]. An example of a swinging motion situation when arresting a fall from a height and impacting a flat obstacle with the head is shown in Figure 3.2.

When considering the provision of safety helmets for workers, it is essential to analyse the atmospheric conditions in which they are to be used. This applies primarily to the temperature ranges, i.e. the lowest and highest ambient temperatures. Testing of safety helmets, provided in the report by Baszczyriski [2011] and the article by Baszczyriski [2014], showed significant sensitivity of their protective properties to variations in temperature at which they are used. Decrease in the shell and harness strength, as well as deterioration of shock absorption properties, manifested by an increased force transmitted to the head of the user during an impact on the helmet of a moving object, constituted the most significant effects observed. The reduction in the strength of the helmet elements in the tests was usually a consequence of initial conditioning at low temperatures (below -20°C). Due to this, during the impact on the helmet mounted on a headform of striker with energy of 49 J (according to the standard EN 397:2012+A 1:2012 [CEN 2012a]), there

Head impact on an obstacle in the swinging motion performed while arresting a fall by personal protective equipment

FIGURE 3.2 Head impact on an obstacle in the swinging motion performed while arresting a fall by personal protective equipment.

were cracks in the shells and ruptures of the harness straps and their attachment points joining the harness with seats in the shell. These effects are dangerous from the user’s safety point of view, as they constitute a threat of a serious head injury or a rapid increase in the force transmitted to the head and cervical vertebrae. Another dangerous phenomenon, associated with the ambient temperature changes during the use of helmets (mainly its increase), is softening of the materials they are made of. This effect concerns the helmet shell and harness, and is sometimes manifested already in temperatures of 50°C [Baszczyhski 2014]. As the material softens, with the same impact energy, the deflection of the shell and the elongation of the harness straps increase. During the testing simulating such a situation, the shell was driven in to a headform, and in real conditions this would be the head of the user. It was associated with an increase in the force transmitted to the headform, which is shown in Figure 3.3.

The tests results presented in the report by Baszczyhski, Jachowicz and Jablonska [2011] and in the article by Baszczyhski [2014] showed that with regard to most helmet structures, the helmets’ pre-conditioning temperature increases before impact, reducing the shock absorption capacity. The shock absorption capacity is understood here as the value of kinetic energy of the striker impact, in relation to which the value of the force transmitted to the headform reaches 5 kN, according to EN 397:2012+Al:2012 [CEN 2012a]. The aforementioned test results clearly indicate that an accurate examination of thermal conditions concerning the helmet use

has a very significant impact on the safety of their users.

t(s)

FIGURE 3.3 The course of the force transmitted by the helmet to a headform during an impact of a striker with the energy of 49 J with a characteristic peak, which accompanies the contact of the helmet shell with the headform.

Hot factors in the working environment may also take other forms, such as molten metal splashes, high intensity infrared radiation, open flames, etc. As these may adversely affect the protective properties of the helmets, it is necessary to use designs that guarantee the appropriate properties in this situation. With regard to helmets resistant to molten metal splashes, the shells thereof must be made of material that is not subject to melting, deformation and ignition under the influence of liquid metal particles. In the case of a helmet resistant to intense infrared radiation, the shell thereof must be covered with material reflecting that radiation, e.g. a layer of sprayed metal, which prevents it from overheating. Some structures of infrared resistant helmets are also equipped with a lining that additionally insulates the head of the user.

In industrial conditions, there are workstations where helmets can be exposed to aggressive chemicals. Repeated exposure of the helmet to such substances may result in degradation of the materials they are made of and, consequently, loss of protective properties. Therefore, the decision to use the helmet in such a workstation must be consulted with its manufacturer unless there is adequate information in the instructions for use. Helmets intended for firefighters, meeting the requirements of standard EN 443:2008 [CEN 2008], constitute examples of helmets whose resistance to aggressive chemicals is verified in laboratory tests.

When working in the vicinity of the elements under electric voltage, it is necessary to choose a helmet that has appropriate electrical insulating properties. Such a helmet must protect the user against electric shock, as well as prevent a short circuit, e.g. by touching the helmet shell to two electric wires.

The shells of certain types of protective helmets, due to the material from which they are manufactured, are capable of collecting electrical charges. This property may lead to spark discharges which are dangerous when helmets are used in an explosive atmosphere, e.g. coal mines endangered by methane. These conditions require helmets with antistatic properties, i.e. helmets resistant to electrification and with shells of a low surface resistance, neutralizing the accumulated charge.

The selection of helmets for a specific workplace should also factor in the exposure to UV radiation, which is one of the main factors causing degradation of plastics and, consequently, their ageing. UV radiation sources may be both, natural, i.e. the Sun, and artificial, such as an electric arc during welding. When selecting helmets for such workplaces, attention should be paid to the manufacturers’ recommendations in this respect and the helmets with shells sensitive to UV radiation should be avoided, e.g. polythene with no stabilizing additives.

An important aspect of helmet selection is the intention to use them simultaneously with other personal protective equipment, e.g. eye and face protectors, respiratory protective equipment, hearing protectors and protective clothing. In such a situation, helmets must be fitted in such a way that they are compatible with other equipment, i.e. no new hazards are created concerning their user and no protective function of the individual components is impaired. The materials provided by manufacturers of protective equipment, should be the basic source of information in this respect.

The efficiency of the head protection with a helmet is determined not only by the selection, but also by its proper use. Therefore, the following basic principles of using protective helmets were formulated:

  • • Before use, the helmet should be fitted to the head dimensions by a proper adjustment of headband circumference, wearing height and chin strap length.
  • • The helmet must be removed of service if it was subject to a severe impact or shows signs of damage.
  • • The helmet must be removed of service if its life-span has expired, as provided by the manufacturer in the instructions for use.
  • • The helmet should be stored in the conditions provided by the manufacturer, that do not result in loosing protective parameters.
  • • Modification of the helmet construction by the user is prohibited.
  • • Helmet maintenance should be carried out using methods recommended by the manufacturer.
 
Source
< Prev   CONTENTS   Source   Next >