Analytical method using SEM-EDS for metal elements present in particulate matter generated from stainless steel flux-cored arc welding process.

Welding fumes (WFs) can cause occupational pneumonoconiosis and other diseases in workers. WFs have complex chemical composition and morphology depending on the welding conditions. The WF surface is a key factor affecting those diseases. The objective of this study was to establish an analytical method focused on characterizing individual WFs and welding slags (WSs) formed during CO2 arc welding processes for knowledge acquisition of risk assessment. Especially, the characterization was focused on the elemental distributions near the surfaces obtained using fluxing agents and size of the WFs. WFs were collected using personal samplers. After welding, WS was also collected. The fluxing elemental distribution (e.g., Bi) near the surfaces WS and WFs were analyzed through scanning electron microscopy and energy-dispersive X-ray spectroscopy. As a result, some of the micron-sized spherical particles (SPs) grew by incorporating nanosized primary particles composed of other metal species. The fluxing agents formed elemental distribution patterns on the SP surface. Bi were dotted in an agglomerate. Mn amount in WS depends on Mn amount in the WFs. These results obtained through the analysis of both the WS and WF surface as well as the particle sizes will facilitate the establishment of exposure assessment models.

Prevention against carbon monoxide poisoning emanating from burning coal briquettes - Generation rate of carbon monoxide and ventilation requirement.

Carbon monoxide (CO) poisoning accidents occur every year in Japan, most of which are caused by the incomplete combustion of fuel, such as gasoline, light oil, and coal briquettes. To prevent CO poisoning in workers, it is essential to reduce the CO concentration in a working environment below the criteria threshold through ventilation. Although proper ventilation requirements for enclosed spaces are estimated from the generation rate of air pollutants, there is no empirical research evaluating the CO generation rate of coal briquettes. In this study, the author evaluated the CO generation rate of burning coal briquettes under controlled laboratory conditions and estimated the appropriate corresponding ventilation requirements. Despite the coal briquettes were burned under sufficient oxygen supply, the CO generation rates and the briquettes' consumption rates were 146-316 mL/min/kW and 1.65-3.61 g/min, respectively. Assuming the CO concentration limit was 50 ppm, the corresponding ventilation requirement was 174.9-378.7 m3/h/kW. The ventilation requirement was 43.7-94.7 m3/h/kW when the critical CO concentration was set at 200 ppm. Adopting the ventilation requirements set out in this study could facilitate proper ventilation and reduce the risk of CO poisoning.

Features of the Japanese Industrial Safety and Health Act: some key points regarding the organization of safety and health management.

The Japanese Industrial Safety and Health Act was first enacted in 1972. The purpose of this Act is to secure the safety and health of workers in the workplace, as well as to facilitate the establishment of a comfortable work environment. To fulfill these purposes, the Industrial Safety and Health Act aims to clarify the responsibility system in the workplace and to promote proactive efforts by both employers and employees to maintain safety and health in the workplace. Specifically, it is expected that occupational accidents will be prevented by obligating employers to appoint safety and health personnel in accordance with the Act. In this paper, I introduce the features and key points of the Industrial Safety and Health Act, especially in relation to Chapter 3 (Articles 10-19), which provides for the organization of the safety and health management system. In addition, I describe recent amendments to the Act.

"Purchase survey" of respiratory protective equipment as a follow-up on the national certification system in Japan.

Since respiratory protective equipment (RPE) are essential for the workers who are occupationally exposed to harmful airborne substances, it is necessary to complete a strict certification test on RPE. In Japan, Technology Institution of Industrial Safety (TIIS) is responsible for the RPE certification and examines the RPE submitted by the manufactures to make an admission decision with the national standards. However, the certification system cannot ensure the quality of the RPE after the shipping because some RPE may deteriorate during the distribution process or the storage period at retail stores. In this article, the author aimed to introduce the follow-up system on national RPE certification in Japan and the role of the follow-up survey committee established by TIIS.

Decline of the performance of a portable axial-flow fan due to the friction and duct bending loss of a connected flexible duct.

OBJECTIVES: In a job site, a portable fan is often used to ventilate a confined space. When a portable fan is applied to such a space, the actual ventilation flow rate must be accurately estimated in advance because the safety level of contaminant and oxygen concentrations in the space will determine the ventilation requirements. When a portable fan is used with a flexible duct, the actual flow rate of the fan decreases due to the friction and duct bending loss of the duct. Intending to show the decline of a fan performance, the author conducted laboratory experiments and reported the quantitative effect of the friction and duct bending loss of a flexible duct to the flow rate of a portable fan. METHODS: Four commercial portable fans of different specifications were procured for the experiments, and the decline of the performance of each portable fan due to the friction loss etc. of a connected flexible duct was investigated by measuring actual flow rate. RESULTS: The flow rate showed an obvious decrease from the rated flow rate when a flexible duct was connected. Connection of a straight polyester flexible duct and a straight aluminum flexible duct reduced the flow rates to 81.2 - 52.9% and less than 50%, respectively. The flow rate decreased with an increase of the bend angle of the flexible duct. CONCLUSION: It is recommended that flow rate check of a portable fan should be diligently carried out in every job site.

Generation rate and particle size distribution of wood dust by handheld sanding operation.

OBJECTIVES: The International Agency for Research on Cancer (IARC) and Japan Society for Occupational Health (JSOH) classified wood dust as a human carcinogen. Former studies have suggested that sanding with a portable sander is one of the processes that are liable to cause highest exposure to wood dust. However, the wood dust by sanding operation has not been investigated sufficiently. In this study, the generation rate and the particle size distribution of the wood dust produced by handheld sanding operation were observed by laboratory experiments. METHODS: Beech and cypress were taken as typical hard and soft wood specimen respectively, and sanded with a portable sander. Three grades of sand paper (coarse, medium, fine) were attached to the sander in turn to be tested. The quantity of the wood dust produced by the sander was measured by weighing the specimen before and after the sanding and then the generation rate of the dust was calculated. RESULTS: Soft wood generated more dust than hard wood due to the difference in abrasion durability. A coarse sand paper produced more dust than a fine sand paper. The particles of less than 1 µm diameter were scarcely observed in the wood dust. When the specimens were sanded with a fine sand paper, the mass median aerodynamic diameters of beech dust and cypress dust were 9.0 µm and 9.8 µm, respectively. CONCLUSIONS: Respirable wood dust is able to be controlled by general ventilation with more than 0.7-4.2 m3/min ventilation rate.

An Empirical Study on the Wake Around a Squatting Worker in a Confined Space.

Objectives: When an air current flows from behind a worker, the contaminant level in the breathing zone may increase due to the wake around the worker. Researchers have been investigating about this wake, and much knowledge has been provided about the wake that appears around a standing worker. However, the wake around a squatting worker has not been addressed. This study aimed to describe the wake in front of a worker squatting in a confined space by using a model worker and a chamber and investigate the conditions in which this wake develops easily. Methods: A mannequin was employed as a model worker and was placed in the chamber to simulate a squatting worker in a confined space. Then, air was sent from behind under various conditions with a fan, and the wake was observed. Results: A wake appeared when smoke was emitted at 0-0.1 m from the point just below the breathing zone, and most of the wake region was in the range between the point just below the model worker's breathing zone and body. A wake did not appear when a fan of 0.15 m in diameter was used. The flow rate and velocity of the airflow were almost irrelevant with respect to wake development. Conclusions: The following are recommended based on the results of the present study. ⅰ) The distance between a source of contaminants and the point just below the breathing zone should be more than 0.2 m. ⅱ) An air duct with a cross-section of less than 0.02 m2 is desirable to avoid producing a wake.

An empirical study on the wake around a squatting worker in a confined space.

OBJECTIVES: When an air current flows from behind a worker, the contaminant level in the breathing zone may increase due to the wake around the worker. Researchers have been investigating about this wake, and much knowledge has been provided about the wake that appears around a standing worker. However, the wake around a squatting worker has not been addressed. This study aimed to describe the wake in front of a worker squatting in a confined space by using a model worker and a chamber and investigate the conditions in which this wake develops easily. METHODS: A mannequin was employed as a model worker and was placed in the chamber to simulate a squatting worker in a confined space. Then, air was sent from behind under various conditions with a fan, and the wake was observed. RESULTS: A wake appeared when smoke was emitted at 0-0.1 m from the point just below the breathing zone, and most of the wake region was in the range between the point just below the model worker's breathing zone and body. A wake did not appear when a fan of 0.15 m in diameter was used. The flow rate and velocity of the airflow were almost irrelevant with respect to wake development. CONCLUSIONS: The following are recommended based on the results of the present study. i) The distance between a source of contaminants and the point just below the breathing zone should be more than 0.2 m. ii) An air duct with a cross-section of less than 0.02 m(2) is desirable to avoid producing a wake.

Generation rate of carbon monoxide from CO2 arc welding.

OBJECTIVES: CO poisoning has been a serious industrial hazard in Japanese workplaces. Although incomplete combustion is the major cause of CO generation, there is a risk of CO poisoning during some welding operations. The aim of the present study was to evaluate the generation rate of CO from CO2 arc welding under controlled laboratory conditions and estimate the ventilation requirements for the prevention of CO poisoning. METHODS: Bead on plate welding was carried out with an automatic welding robot on a rolled steel base metal under several conditions. The concentration of emitted CO from the welding was measured by a real-time CO monitor in a well-ventilated laboratory that was free from ambient CO contamination. The generation rate of CO was obtained from the three measurements-the flow rate of the welding exhaust gas, CO concentration in the exhaust gas and the arcing time. Then the ventilation requirement to prevent CO poisoning was calculated. RESULTS: The generation rate of CO was found to be 386-883 ml/min with a solid wire and 331-1,293 ml/min with a flux cored wire respectively. It was found that the CO concentration in a room would be maintained theoretically below the OSHA PEL (50 ppm) providing the ventilation rate in the room was 6.6-25.9 m3/min. The actual ventilation requirement was then estimated to be 6.6-259 m3/min considering incomplete mixing. CONCLUSIONS: In order to prevent CO poisoning, some countermeasures against gaseous emission as well as welding fumes should be taken eagerly.

[Airflow equation of a slot hood by the least square method].

OBJECTIVES: In designing a local exhaust ventilation (LEV) system, the exhaust airflow rate which will produce the required control velocity at the capture point must be predicted properly. Conventionally, the airflow requirements for LEV hoods have been calculated using Dalla Valle's equation. Although Dalla Valle's equation is a simple and convenient formula for LEV design, it is known that the airflow rate predicted by the equation does not always coincide with actual exhaust airflow rate. In order to develop a new airflow formula which can substitute for Dalla Valle's equation, the author aimed to develop an empirical airflow formula for a slot type exhaust hood using the least square method. METHODS: Based on the actual measurements (exhaust airflow rate, suction velocity, hood size and centerline distance) of test slot type hoods in several configurations and conditions, an empirical approximation formula which predicts exhaust airflow rate was developed. In this study, the approximation formula was described as a polynomial linear expression, and the validity of the predicted exhaust airflow rate by the approximation formula was confirmed by comparing with measured airflow rates. RESULTS: It was found that the predicted airflow rates of the developed approximation formula were in good agreement with the measured airflow rates and were more accurate than the airflow rates predicted by Dalla Valle's equation. CONCLUSIONS: Although the applicability of the developed formula is inferior to that of Dalla Valle's equation, certain economic benefits can be derived from the developed formula in some cases.

Gaseous contaminant distribution in the breathing zone.

Conventionally, the "breathing zone" is defined as the zone within a 0.3 m (or 10 inches) radius of a worker's nose and mouth, and it has been generally assumed that a contaminant in the breathing zone is homogeneous and its concentration is equivalent to the concentration inhaled by the worker. However, several studies have mentioned that the concentration is not uniform in the breathing zone when a worker is close to the contaminant source. In order to examine the spatial variability of contaminant concentrations in a worker's breathing zone, comparative measurements of personal exposure were carried out in a laboratory. In experiment, ethanol vapor was released in front of a model worker (human subject and mockup mannequin) and the vapor concentrations were measured at two different sampling points, at the nose and at the chest, in the breathing zone. Then, the effects of the sampling location and the body temperature on the exposure were observed. The ratios of nose concentration to chest concentration for the human subject and the mannequin were 0-0.2 and 0.12, respectively. The exposure level of the mannequin was about 5.5-9.3 times higher than that of the human subject.

Measuring exposed magnetic fields of welders in working time.

The assessment of the occupational electromagnetic field exposure of welders is of great importance, especially in shielded-arc welding, which uses relatively high electric currents of up to several hundred amperes. In the present study, we measured the magnetic field exposure level of welders in the course of working. A 3-axis Hall magnetometer was attached to a subject's wrist in order to place the sensor probe at the closest position to the magnetic source (a cable from the current source). Data was acquired every 5 s from the beginning of the work time. The maximum exposed field was 0.35-3.35 mT (Mean ± SD: 1.55 ± 0.93 mT, N=17) and the average value per day was 0.04-0.12 mT (Mean ± SD: 0.07 ± 0.02 mT, N=17). We also conducted a finite element method-based analysis of human hand tissue for the electromagnetic field dosimetry. In addition, the magnetic field associated with grinders, an air hammer, and a drill using electromagnetic anchorage were measured; however, the magnetic fields were much lower than those generated in the welding process. These results agreed well with the results of the electromagnetic field dosimetry (1.49 mT at the wrist position), and the calculated eddy current (4.28 mA/m(2)) was much lower than the well-known guideline thresholds for electrical nerve or muscular stimulation.