Operating safety of personal protective equipment (PPE) including electronic circuits

Status:

completed 12/2002

Aims:

Personal protective equipment (PPE) featuring integrated electronic circuits has been available for some time now. This new generation of personal protective equipment has brought with it a number of changes. In equipment featuring welding filters, dynamic liquid crystal filters provide a higher level of user comfort. In equipment featuring hearing protectors, the circuits provide active noise compensation (anti-sound), level-related protection, or audio communications. In the past, compressed-air breathing apparatus (SCABA) was equipped with conventional mechanical, hydraulic or pneumatic display systems for the remaining air pressure. Integrated electronic circuits replace the acoustic signal that the critical pressure values have been reached. The objective of the project was to answer questions concerning the safety level of these new features. New risks which may arise under anticipated conditions of use must be taken into consideration, such as satisfactory resistance to environmental influences (climatic, mechanical, electrostatic, electromagnetic). The project was to examine whether consideration is given in European standards to the safety requirements for personal protective equipment which arise in relation to the use of integrated electronic circuits. Proposals for corresponding amendments to these standards had been to be drawn up.

Activities/Methods:

In order to assess the level of protection, risk evaluation were performed in accordance with the systems employed in the area of machine safety (DIN EN 954-1: 1997: Safety of machinery; Safety-related parts of control systems; Part 1: General principles for design). Categories for reliability and risk assessment of integrated electronic circuits in machines and their associated safety components were drawn up for this standard. An electro-optical welding filter, three hearing protector types (anti-sound, level-dependent, and integrated communications) and one item of compressed air breathing apparatus (SCABA) have been examined based upon these categories in accordance with DIN EN 1050: 1997: "Safety of machinery; Principles for risk assessment". The emphasis was upon fulfilment of the nominal safety function within a particular environment, and the anticipated fault-mode behaviour.

Results:

The laboratory test procedures developed by INRS and BIA for studying the resistance to ambient influences of electronic circuits integrated into PPE were tested and improved on a standard item of compressed-air breathing apparatus (INRS), three hearing protector types (BIA), and one electro-optical welding filter (INRS), in all cases purchased commercially. The function of all electronic circuits integrated into these items of PPE was influenced by climatic, mechanical, electrostatic and electromagnetic ambient factors. The hearing protectors exhibited additional problems concerning the electrical microphones; these problems require further clarification. The results of the studies of the compressed-air breathing apparatus formed the basis for formulation by INRS and BIA of a proposed method for an annex to European test standard EN 137, "Respiratory protective devices - Self-contained open-circuit compressed air breathing apparatus - Requirements, testing, marking", and its inclusion in CEN/ISO standardization activity (CEN/TC 79, "Respiratory Protective Equipment"). The results of the study of the electro-optical welding filter are to be introduced into European standardization activity during future revision of EN 379, "Specifications for welding filters with switchable luminous transmittance and welding filters with dual luminous transmittance" (INRS).

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