In this study, a novel explosion test equipment along with a testing methodology were introduced to evaluate the ignitability of electrostatic coating guns for ignitable liquid coating materials. The explosion test equipment consisted of an explosion chamber, an electrostatic coating gun, a grounded metal ball electrode with 25 mm in diameter, a small sized robot, a gas concentration meter, and a personal computer to control the robot. The explosion chamber was filled with air containing approximately 5.25 vol ％ propane. Three kinds of electrostatic coating guns （S1 to S3） were used for ignition tests. The results showed that the safety function device effectively prevented ignitions for all the electrostatic coating guns. However, an ignition was detected on the S2 electrostatic coating gun when the safety function device was off. The ignition was attributed to a non-grounded metal paint spray part existing near the needle electrode. The results obtained by employing the explosion test equipment and method introduced in this study were confirmed to be valid and reproducible．

To objectively evaluate eye fatigue caused by working with visual display terminals （VDT）, we examined the pupillary light reflex as a physiological index, using a pupillary light reflex analyzer. The study involved 25 participants （12 male and 13 female） aged between 21 and 23 years （mean 21.8 years）. The participants performed a task using number-search task software; this simulated VDT work for 1 hour. Before and after performing the task, the participants filled a subjective symptom questionnaire and their pupillary light reflex was measured using a single light stimulation test. Eleven participants （four male and seven female; mean age, 21.7 years） also underwent ten consecutive light stimulation tests. Light stimulation to the eyes was provided using LED （red, 635 nm; blue, 470 nm） before and after the task. The difference in the pupillary light reflexes before and after the task was recorded. The subjective symptom survey revealed significantly more complaints of eye fatigue after the task than before the task （p<0.05）. Results of the single light stimulation test showed that the rate of constriction （CR） in response to the blue LED after the task was significantly lower in both eyes than that before the task （p<0.05）. The results of the ten consecutive light stimulation tests showed that the CR difference between the first and tenth stimulations using the blue LED was lower after the task than before the task, and a low CR persisted after the task. The above results showed that light reflex measurements may be indicative of eye fatigue, especially the CR, in response to the blue light stimulus. This test may be applied clinically to work management.

Minimum explosible concentrations are important safety information concerning dust explosions. This paper presents the results of numerical simulations of dust explosions under conditions close to the minimum explosible concentrations. Dust explosions are modeled as processes of combustion-wave propagation by heat conduction between particles; a particle releases heat when its temperature reaches an ignition temperature. The source term in the heat conduction equation is expressed as the summation of delta functions, enabling the evolution of temperature distribution to be given in terms of fundamental solutions （Greenʼs functions）. In cases of regularly arranged particle configurations, analytical expressions can be obtained for propagation speed and minimum explosible concentration. Numerical simulations were conducted for random particle configurations, reproducing results that are consistent with previous experiments. The influence of particle-size distribution on propagation speed and minimum explosible concentration is additionally studied.

The industrial accidents concerning gas cutting and welding had occurred frequently in Japan. The research institute （JNIOSH） collected the accident information and conducted a field survey. Gas cutting apparatus were collected from many factories and measured their performance. The collection work was done with the cooperation of the Japan Welding Engineering Society （JWES）. In this paper, only the results of the gas cutting torches （blowpipes） were described. 31 blowpipes for acetylene and 43 for LPGs were collected from 32 factories. The collected blowpipes had been used for 2 to 18 years. We analyzed collection questionnaires and conduced the following tests: visual inspection, leak tests, and disassembly tests for soot deposition. As a result of these measurements, it was found that the cutting oxygen tube and the neck （mixed gas tube） of the blowpipe were bent, and there were many leaks at the connection between the neck and the mixing chamber as a defect. Approximately 40％ of the blowpipes had poor valve blockage. Wear and damage to the valve body and the valve seat of the heating oxygen valve were observed, which was considered to be one of the causes of poor blockage and flashback. Although there was no leakage in the leak tests, many blowpipes had soot （flashback marks）, and some of them had flashback from the blowpipe to the fuel gas hose. Based on the measurement, the accident prevention measures were described.