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Copyright of Journal of the Japanese Society of Snow & Ice / Seppyo is the property of Japanese Society of Snow & Ice and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper describes separation performance of newly developed forward cyclones with 7 kinds of size and structure. The forward cyclones have 2 or 4 tangential-air-inlets, a dust pot and a flow receiver for fine particles. Our previous study showed that the cyclones had sharp size separation performance for PM2.5 but did not clarify the mechanism. Size separation characteristics of the cyclones were evaluated using a pair of optical particle counters with test aerosols of standard polystyrene latex particles ranging from 1 to 6 µm in diameter. Also swirling flow in the cyclone was observed by tracer powder. Measured data, such as 50% cut-off aerodynamic diameter at flow conditions of each cyclone, were used to estimate the flowrate branching off the dust pot. Ranging from 3 to 30 percent of total flowrate were passed to the dust pot before flow throughout the cyclone. The flow caused sharp centrifugal separation to the aerosol particles introduced into the cyclone. Smallest the cyclone (bore diameter was 10 mm) covered samplings for PM2.5 fraction of ambient aerosols at 3 L/min and respirable particle faction (PM4) at work environments at 1.7 L/min. Largest the cyclone (bore diameter was 90 mm) fitted to a high-volume air sampler of which flowrate ranged from 150 to 600 L/min, showed the same performance as the smallest one. [ABSTRACT FROM AUTHOR]

Objective: Bacteria on the facepiece of a dust respirator were measured just after use and after 24-hours storage at a room temperature after being worn, and bacteria disinfection methods other than ethanol were examined., Methods: The existence of bacteria on a facepiece of a mask that had been worn for about one hour in a laboratory was investigated. In order to eliminate bacteria before use on the next day, five methods of bacteria disinfection were investigated: wiping with a facial tissue impregnated with ethanol as a control; wiping with a facial tissue wetted with tap water; wiping with a dry facial tissue after wiping with one wetted with tap water; wiping with a dry facial tissue after wiping with one wetted with distilled water; and wiping with a dry facial tissue two times. The tests were carried out using silicone rubber sheets plated with bacteria collected from human skin. The disinfection methods that were as effective as facial paper wetted with ethanol, were then assayed on the facepiece of the dust respirator., Results: Bacteria were detected on the facepiece immediately after it had been worn. Bacteria were also detected on the facepiece after it had been stored at 25°C for 24-hours after being worn. The methods of wiping with a dry facial tissue after wiping with either tap water or distilled water were almost as statistically effective as wiping with ethanol wetted facial paper. Bacteria on the facepiece were decreased by wiping with a dry facial tissue after wiping with one wetted with tap water., Discussion: Colonies of bacteria were detected on a facepiece that had been stored 24 hours after being worn, which suggests that bacteria disinfection just after a respirator has been worn should be recommended. It is very important that the water on the facepiece should be removed after wiping with a wet facial tissue.

In Japan, there are two commonly used regulations on respirable dust concentration: the Occupational Exposure Limit (OEL), recommended by the Japan Society for Occupational Health, and the Administrative Control Level (ACL). Both depend on the crystalline silica content in dust. Until 2004, the ACL for respirable dust conformed to the OEL. However, the ACL was revised in 2005 in light of the OEL and the American Conference of Governmental Industrial Hygienists (ACGIH)'s Threshold Limit Value (TLV), same value as National Institute for Occupational Safety and Health (NIOSH)'s Recommended Exposure Limit (REL). In this paper, the author intends to clarify the stringency of the current ACL by comparing it with the OEL and the ACGIH's TLV. In addition, the effect of the analytical error due to the phosphoric acid method in the current and former ACLs is shown.

Dust collectors with bag filters are widely used to remove hazardous aerosols in work environments. Package type dust collectors, which include a fan and motor, differ in a wide variety of ways, such as the inner structure, the filter media, methods for cleaning collected dust, and flow control methods. In this study we focus on the performance of dust collectors for respirable dust fraction, which can reach the lung alveoli and cause pneumoconiosis. We surveyed the actual situation of dust collectors at worksites by means of light scattering photometers with PM2.5 cyclones, measured the details of performance of a typical dust collector using common test dust (Atomite) in a laboratory, and then tested the collection efficiency of the filter samples with and without dust load. The test aerosols for the filter samples were generated by the nebulization of standard monodisperse particles (Polystyrene latex particles, 0.6 to 3 μm). The penetration measured by photometers with PM2.5 cyclones approximated the performance of dust of 1.2 μm in nominal size. We propose the test methods at worksites and the filter media of bag filters in confirming the performance of dust collectors. [ABSTRACT FROM AUTHOR]