This paper reports the results of the measurement of the thermal environments and workers responses which included evaluation of the thermal environments in the "Cool Biz" implemented office. The measurement was conducted an older standard building in the middle of Tokyo in September 2005. Thermal conditions included ambient temperature, relative humidity, air velocity and radiant temperature which were automatically measured every five minutes. As part of the questionnaires, the thermal sensation vote, comfort vote and actual clothing worn were measured. Each worker was also asked regarding their preferences and physical characteristics. The thermal conditions in the office were relatively acceptable range, although ambient temperature was approximately under 28.0°C. However, the workers perceived the thermal conditions differently. The mean of the clo value was 0.53, which showed that the workers wore very light summer clothes. The male subjects did not wear jackets in the office and 12% of them wore put neckties. The mean value of PMV of each worker was 0.50 and PPD was 12.4%. The perception of women was rather neutral, although that of men was diverse. It was considered that this diversity was due to the personal constitution. A proposal was made which indicated the thermal condition of PMV=+0.5 in the room of 28°C was perceived as more comfortable environment.
In Japan, metal-framed occupational safety glasses are as common as those with plastic frames. However, metal frames can sometimes release nickel, which can cause allergic contact dermatitis in some wearers. In this study, 39 pairs of metal-framed occupational safety glasses, selected from 29 models commonly used in Japan, were tested and evaluated for nickel release using the same basic ISO-provided method established for normal prescription eyeglasses. The rims of 20 samples (51%), and the temples of 11 samples (28%), were found to release amounts of nickel that exceed established ISO limit. Combining both results, 23 samples (59%) were found to release nickel amounts exceeding set limit from either the rims or the temples, and were therefore determined to be unacceptable. This indicates that a significant percentage of the metal-framed occupational safety glasses used in Japanese workplaces could release sufficient amounts of nickel to cause contact dermatitis in some workers. It is thus considered necessary to determine the prevalence of contact dermatitis caused by such metal-framed occupational safety glasses.
A pile driver is a large construction machine used for ground improvement and foundation work. In recent years, there have been some reports of accidents in which the machine overturned. An investigation revealed that overturning accidents often occur while the machine is relocating to another pile. In this study, to clarify the mechanism which makes the pile driver unstable when it is self-propelled, real-scale experiments were performed. The behavior of the pile driver was measured by putting three-axis accelerometers in three places: the upper part and lower part of the leader, and the crawler base. The experiments were conducted under two conditions, straight and curved, on flat, firm ground. As a result, it was discovered that the pile driver was subject to long periodic shaking during self-propelling. The degree of shaking in response to acceleration on the curved course was large, and it was clarified that turning makes the machine unstable.
In the chemical industry, there have been numerous reports on mechanical damage, such as pinholes, due to electrostatic discharge on the wall of glass-lined (GL) chemical vessels, in which slurries containing low-conductive liquid and low-soluble powder undergo vigorous stirring. To address this problem, we have developed an easy-to-operate, desktop electric field measuring system for predicting the charge generation in a GL vessel containing a slurry. This system includes a two-liter stirring vessel of glass covered with metal foil provided with electrostatic field sensors. Many combinations of solvent and powder were tested using this system. The electric field strengths on the wall of the testing vessel depended on the behavior and the conductivity of the slurries, the powder solubility, the stirrer revolutions, etc. The typical distribution and trends of electric fields during stirring were discovered. A practical screening method to identify potentially hazardous slurries in advance using our apparatus is proposed.
This study proposes the simplest way of performing an investigation into the cause of an occupational accident. A typical approach is the basic cause analytical method based on the 4Ms (Man, Machine, Method, Management). However, the results of this analysis on 129 fatal accident cases indicate that 60 percent or more of those accidents can be attributed to causes such as incomplete communication or configuration management. Consequently, an attempt is made to extract fundamental causes by adding a time-oriented (or life-cycle) analysis to the "what's and why's analysis" methods of the conventional 4Ms and the informational causes. However, extraction of the basic causes is not always linked to clarification of specific substantive accident prevention measures. Therefore, an additional study is performed to examine the fundamental cause determination method in order to clarify the fundamental causes from the viewpoints of (a) ethics, (b) technology, (c) organizational management and (d) social systems. This is referred to as the fundamental cause determination method based on the BFI matrix (Basic, Fundamental, Inherently). In this case, useful references involve the "Comprehensive machinery safety standard" published in 2006 as well as "Safety management methods using IT". Furthermore, in terms of technical measures relating to change control procedures, what is believed to be useful is building a support system (called the configuration management system), in which the methods under development in the functional safety field (IEC61508 et al.), the quality management field (ISO09000 family) and the project management field (PMBOK, et al.) are extended to include even the configuration management in the occupational safety field. The above-mentioned method is used for occupational accident analyses relating to the use of large centrifugal machines. As a result, an inherently reliable accident prevention measure is clarified and its effectiveness is demonstrated.
Recently, with the development of the ozone generator, it has become possible to obtain high concentration of ozone up to 15vol.% in oxygen. In the previous study, the decomposing explosion properties and the flame propagation behavior of high concentration ozone in a closed vessel were clarified, but the minimum ignition energy was not. To ensure safe handling of ozone, its decomposing properties must be understood. In this study, the minimum ignition energy of an ozone/oxygen gas mixture of up to 15 vol.% of ozone in oxygen under atmospheric pressure in a closed vessel was investigated. A stainless steel cylinder (106mm i.d., 114mm in height, 1.0L in volume) was used as the explosion vessel. An electric spark by capacitor discharge was used for ignition. The energy was evaluated based on 0.5CV2. The experimental results are as in follows: 1) The minimum ignition energy at 15vol.% ozone in oxygen was 10mJ. 2) Higher concentrations of ozone showed lower minimum ignition energies. 3) The lowest minimum ignition energy of 14vol.% ozone in oxygen was observed with 3-4mm electrode distance. 4) It was confirmed that the quenching distance is approximately equivalent to the spark gap distance at the lowest ignition energy of the energy-versus-distance curve.