An Adaptive System for Active Noise Reduction Grzegorz Makarewicz, Grzegorz Matuszewski, Leszek Morzyński, Wiktor Zawieska, 13-22 Measurement of the Response Time of an Electrosensitive Protective Device in the Process of Its Certification Marek Dźwiarek, 23-33 Prediction of Toxic Substances Emission for Occupational Exposure Assessment Krzysztof M. Benczek, Ewa Gawęda, Joanna Kurpiewska, 35-43 A Study of the Nonsteady-State Filtration Process in a Fibrous Material in Conditions of Real Dust Loading Katarzyna Majchrzycka, 45-58 Monitoring Psychosocial Stress at Work: Development of the Psychosocial Working Conditions Questionnaire Maria Widerszal-Bazyl, Roman Cieślak, 59-70 Impact of Economic Incentives on Costs and Benefits of Occupational Health and Safety Zofia Pawłowska, Jan Rzepecki, 71-83

Notes:

Occupational Health and Safety Management in Polish Enterprises Implementing Total Quality Management Systems Daniel Podgórski, 85-101 Polish System of Assessing Occupational Risk Posed by Chemical Compounds Małgorzata Pośniak, Jolanta Skowroń, 103-109 Preferred Levels of Auditory Danger Signals Jan Żera, Arkadiusz Nagórski, 111-117 Practical Application of Ergonomic Settings of Typical Computerised Workstations Tomasz Tokarski, Danuta Liu, Joanna Kamińska, 119-126 Assessment of Psychophysical Abilities of People with Disabilities During Occupational Rehabilitation Bożena Kurkus-Rozowska, Andrzej Najmiec, Tomasz Tokarski, Maria Konarska, 127-134 Thirst and work capacity of older people in a hot environment Anna Marszałek, 135-142 Review of Research Studies of Ergonomic Aspects of Selected Personal Protective Equipment Katarzyna Szczecińska, Krzysztof Łężak, 143-151

An Adaptive System for Active Noise Reduction
Grzegorz Makarewicz, Grzegorz Matuszewski, Leszek Morzyński, Wiktor Zawieska

An adaptive system for active noise reduction in an acoustic duct is presented. The system is based on a modification of a least mean square (LMS) algorithm called filtered-U with on-line error path modelling. The system was assembled and examined on a laboratory test stand in the Laboratory of Active Noise Reduction Methods of the Central Institute for Labour Protection (Warsaw, Poland). The structure of the test stand, the block structure of the active noise reduction system, the basic assumption concerning the applied adaptive algorithm, and examples of measured effectiveness of the system for various kinds of noise are presented.

Measurement of the Response Time of an Electrosensitive Protective Device in the Process of Its Certification
Marek Dźwiarek

In the process of testing an electrosensitive protective system, determining its response time is of crucial importance. A unique double penetration method of measuring electrosensitive protective device (ESPD) response time has been worked out in the Central Institute for Labour Protection. In the first step, low speed penetration enables the detection zone border to be localised. In the second step of measurement, the probe is injected at a high speed and response time is measured. Three different ways have been taken for validation of the method: theoretical analysis, calibration of the stand, and taking a series of measurements. The double penetration method enables ESPD response time measurement results to be obtained, the accuracy, repeatability, and reproducibility of which is satisfactory enough to be assessed objectively.

Prediction of Toxic Substances Emission for Occupational Exposure Assessment
Krzysztof M. Benczek, Ewa Gawęda, Joanna Kurpiewska

Methods for predicting organic solvents, chromic acid, mineral oil, styrene, and sulphuric acid emissions in painting, metal degreasing, wood preservation, chromium electroplating, turning, grinding, making glass fortified polyester laminates and lead batteries charging, injection moulding of polystyrene plastics, and making polyurethane foam processes are described. Experimentally introduced equations are based on the essential parameters of these processes. Knowing the emission and the total flow rate of ventilation, it is possible to calculate toxic agent concentration, which is the basis of occupational exposure assessment.

A Study of the Nonsteady-State Filtration Process in a Fibrous Material in Conditions of Real Dust Loading
Katarzyna Majchrzycka

The study concerns ways to describe filtration efficiency and gas flow resistance while particles are deposited in fibrous respiratory protective filters under conditions characteristic for their use. The performance of fibrous filter materials of varied structure and electrostatic properties was studied, using polydisperse coarse-grained aerosols and submicron aerosols of sodium chloride. Evidence was found that changes in airflow resistance depended to a large extent on air humidity and the concentration of the aerosol. A relationship was also found between the electrostatic properties of filter media and their decreasing efficiency with time. A numerical model was developed to simulate the phenomenon of nonsteady-state filtration for 2 mechanisms of deposition, which permitted assessment of the filtration characteristics of filter media of any design and in any conditions.

Monitoring Psychosocial Stress at Work: Development of the Psychosocial Working Conditions Questionnaire
Maria Widerszal-Bazyl, Roman Cieślak

Many studies on the impact of psychosocial working conditions on health prove that psychosocial stress at work is an important risk factor endangering workers' health. Thus it should be constantly monitored like other work hazards. The paper presents a newly developed instrument for stress monitoring called the Psychosocial Working Conditions Questionnaire (PWC). Its structure is based on Robert Karasek's model of job stress (Karasek, 1979; Karasek & Theorell, 1990). It consists of 3 main scalesľJob Demands, Job Control, Social Supportľand 2 additional scales adapted from the Occupational Stress Questionnaire (Elo, Leppanen, Lindstrom, & Ropponen, 1992), Well-Being and Desired Changes. The study of 8 occupational groups (bank and insurance specialists, middle medical personnel, construction workers, shop assistants, government and self-government administration officers, computer scientists, public transport drivers, teachers, N = 3,669) indicates that PWC has satisfactory psychometrics parameters. Norms for the 8 groups were developed.

Impact of Economic Incentives on Costs and Benefits of Occupational Health and Safety
Zofia Pawłowska, Jan Rzepecki

The most common type of economic incentive used in the field of health and safety is experience rating of insurance premiums. The impact of this incentive on occupational health and safety (OHS) costs in the company was analysed by comparing insurance costs with other OHS costs associated with inadequate working conditions, such as accident costs borne by a company. Accident costs were estimated on the basis of research carried out in 10 companies. Insurance costs and their adjustments according to the health and safety level in a company were calculated according to an experience rating model developed in the Central Institute for Labour Protection.

Occupational Health and Safety Management in Polish Enterprises Implementing Total Quality Management Systems
Daniel Podgórski

Total Quality Management (TQM) is defined as the management approach of the organization aimed at long-term success through client satisfaction, and which benefits all members of the organization and society (ISO 8402; International Organization for Standardization, 1994a). The objective of the study was to evaluate management methods applied to improve working conditions in Polish enterprises implementing TQM. The investigation was conducted in the form of interviews, which covered relevant connections between the TQM concept and occupational health and safety (OHS) systematic management rules.
  The results revealed that the criteria adopted in investigated enterprises for OHS management systems, as well as the implemented management methods and tools, can be evaluated positively. However, many require significant improvement in order to ensure better compliance with the existing law provisions. Elements of OHS management systems also require better integration with the overall management system of the enterprise.

Polish System of Assessing Occupational Risk Posed by Chemical Compounds
Małgorzata Pośniak, Jolanta Skowroń

According to the Polish Labour Code (Ustawa, 1974) employers are legally obligated to provide workers with information about occupational health and safety risks. Maximum allowable concentrations (MAC) and the results of determining chemical compounds in workplace air are used for assessing occupational exposure and risk.
  A computer-assisted system STER, developed in the Central Institute for Labour Protection, helps to register and document occupational risk assessment and all actions resulting from those assessments.

Preferred Levels of Auditory Danger Signals
Jan Żera, Arkadiusz Nagórski

An important issue at the design stage of the auditory danger signal for a safety system is the signal audibility under various conditions of background noise. The auditory danger signal should be clearly audible but it should not be too loud to avoid fright, startling effects, and nuisance complaints. Criteria for designing auditory danger signals are the subject of the ISO 7731 (International Organization for Standardization [ISO], 1986) international standard and the EN 457 European standard (European Committee for Standardization [CEN], 1992). It is required that the A-weighted sound pressure level of the auditory danger signal is higher in level than the background noise by 15 dB. In this paper, the results of an experiment are reported, in which listeners adjusted most preferred levels of 3 danger signals (tone, sweep, complex sound) in the presence of a noise background (pink noise and industrial noise). The measurements were done for 60-, 70-, 80-, and 90-dB A-weighted levels of noise. Results show that for 60-dB level of noise the most preferred level of the danger signal is 10 to 20 dB above the noise level. However, for 90-dB level of noise, listeners selected a level of the danger signal that was equal to the noise level. Results imply that the criterion in the existing standards is conservative as it requires the level of the danger signal to be higher than the level of noise regardless of the noise level.

Practical Application of Ergonomic Settings of Typical Computerised Workstations
Tomasz Tokarski, Danuta Liu, Joanna Kamińska

The goal of the study was to check, with regard to ergonomics, workstations equipped with visual display terminals in selected enterprises. Over 180 workstations were tested in 3 enterprises. Most workstations were equipped with computers. The ergonomics of both the parameters of the basic components of the workstation (i.e., a chair and a desk, and the position of the computer at the workstation and its screen with respect to windows) and lighting fittings were analysed. Typical mistakes in the layout of a workstation were chairs inappropriate for computer work, as well as broken chair adjustment mechanisms, which qualified chairs for repair or replacement. Wrong positioning of monitors on the desk and with regard to windows and lighting fittings was also noted.

Assessment of Psychophysical Abilities of People with Disabilities During Occupational Rehabilitation
Bożena Kurkus-Rozowska, Andrzej Najmiec, Tomasz Tokarski,

Maria Konarska
Designing objective and subjective methods of studying the abilities of disabled people is one of the most important things to be done before employing them. That is why, new assessment methods are proposed. Evaluation as a testing procedure used for defining the abilities of disabled peopleľgeneral capacity, range, and strength of the main groups of muscles and extremities, psychological tests, and many othersľwere developed by an interdisciplinary team. In total, 48 testing procedures, including physiological, psychological, and biomechanical ones, were prepared.
  We also propose another subjective assessment method because it is also very important to know what an individual person with disability needs, wants to do, or what kind of job he or she prefers. The subjective evaluation of abilities, possibilities, and needs might be done by using a questionnaire.
  These testing procedures offer a chance to use the same methods in all diagnostic centres so the criteria of health and work ability will be the same and easily comparable. Using the same tests for assessment will be helpful in observing the results and progress of medical, social, and vocational rehabilitation, too.

Thirst and work capacity of older people in a hot environment
Anna Marszałek

In a hot environment, especially during exercise, the main role of thermoregulative mechanisms is to dissipate excessive heat from the body. The most effective way of heat dissipation is sweat production and its evaporation off skin surface. Intense sweating results in a considerable loss of water and electrolytes. There are some results that indicate lower thirst of older men than young ones in response to a hot environment and osmotic stimuli. Our studies conducted in men of different ages exposed to a hot environment indicated that there were no significant differences in rectal temperature (Tre) or heat storage (S) among groups at rest. Lower Tre and lower S in older men with higher physical capacity for their age than in young ones with average physical capacity was shown. However, in all the experiments significantly lower thirst in older men than in the young was indicated. Special attention should be paid to fluid replacement among workers in a hot environment because of lower thirst and lower hydration of older men. These individuals may be exposed to dehydration risk during prolonged exercise, despite the possibility to tolerate heat strain as well as young ones. Further studies are necessary because of some diversity in the meaning of the results.

Review of Research Studies of Ergonomic Aspects of Selected Personal Protective Equipment
Katarzyna Szczecińska, Krzysztof Łężak

This article is a review of research studies conducted in the Central Institute for Labour Protection (CIOP) on ergonomic aspects of personal protective equipment (PPE) design and use. Research was related to, among other things, a comparison of body strain and work time limitation for users wearing gas-tight and drill suits. Some other studies were connected with the biophysical properties of clothing materials for medical use. On the basis of the measurement results, a proposal of clothing construction with an optimum combination of protection and comfort was created.
  Research leading to the development of test methodology concerning automatic welding filters with switchable luminous transmittance is also conducted in CIOP.
  The article also brings up the subject of designing new PPE assuring a high level of comfort. A model of material to be used under tight protective clothing, an inflammable harness for working at a height, and a model of intelligent clothing that will assist human thermoregulation processes during physical effort are examples of new PPE.