A. Jansson, O. Vesterberg, L. Holmquist, Stockholm University, Stockholm, Sweden.
The exposure of bus and truck drivers to airborne allergens may constitute a health as well as a traffic safety risk. The ordinary vehicle ventilation systems are commonly not adapted to the specific needs of allergic drivers. A potential method for reducing exposure is to clean the air from particles with a recirculating air cleaner while aiming to direct the cleaned air to the breathing zone of the driver. This concept was studied with an electrostatic air cleaner mounted so it would supply cleaned air to the drivers of a bus and of a truck. The public transport bus operated on three bus lines in Stockholm suburbs. The truck driver performed made deliveries in the greater Stockholm area. During these ordinary traffic activities, the exposures of the drivers to allergens, coarse particles, and ultrafine particles were determined during 2 working weeks. Half of the days the air cleaner was in operation and the rest of the days it was shut off. For the bus driver, the exposure of allergens and ultrafine particles were 80% and 100%, respectively, of the outside concentrations with the cleaner shut off. The effect of the cleaner was a 40% reduction of exposure. For the truck driver the exposure of allergens and “total dust” were 24% and 65%, respectively, of the outside concentrations without the cleaner. The effect of the cleaner was a 50% reduction of exposure. The results reflect the differing ventilation conditions of a bus and a truck with the bus representing an environment with a large degree of air exchange with the outside through frequent door openings. For both vehicles the exposure was reduced to half by operating the cleaner and directing the cleaned air towards the driver breathing zone.
J. Friedman, AMEC, Minneapolis, MN.
The scope of applications for cartridge filters has expanded significantly in industrial dust control projects. However, the technology can be used incorrectly in certain applications. The dust control engineer must be familiar with cartridge technology and its application criteria before making the appropriate choices and the selection of this equipment. This presentation will review the fundamentals of cartridge technology and application factors necessary for a successful design. Application criteria and case histories will be presented.
J. Nalbone, University of Texas, Tyler, TX; J. Crowder, Crowder Consultants, Wylie, TX.
Atomizing scrubbers are used for a wide variety of applications in industrial gas cleaning. These scrubbers also remove submicron particles efficiently and the are relatively compact and easy to construct when compared to other control devices of equivalent performance. Initial costs make them an economical collection device; however, the high cost of operation is a limiting factor of the cleaning application of Venturi scrubbers. The cleaning mechanisms of the Venturi scrubber have been extensively studied and are predominantly a function of inertial impaction. Several mathematical models have been developed to estimate pressure drop and collection efficiency of the Venturi scrubbers. These models provide the tools for designers to evaluate new designs or to maximize an existing system by changing operating parameters. Very few of these models are mathematically explicit and most have numerical solutions requiring the use of a computer. These complex models are cumbersome and tedious even when used in normal design, installation, and testing of scrubber performance. Simplified models for efficiency and pressure drop were developed, based on current principles of Venturi scrubber design parameters, including particle size, convergent section, liquid-to-gas ratio, temperature and velocity of the gas, throat length, and divergent section, density of the liquid, and density of the particle. Both of the models are derived from nonlinear regressions of first principle equations, using a differential change in particle concentration. The predictive values of the simplified models are compared to existing complex models to calculate model variance. The operating conditions of the pilot Venturi were used in the simplified model to predict pressure drop and performance and those performance metrics were compared to actual pilot-study data.
A. Valkeapää, I. Raappana, Oulu Regional Institute of Occupational Health, Oulu, Finland.
Open doorways cause draught complaints and heat losses. Air curtains are used to reduce these drawbacks. Typically, passenger traffic doorways are equipped with a horizontal type air curtain. The performance of the air curtain depends on the leakage characteristics of the envelope, weather conditions, and the characteristics of the jet and nozzle used. The goal of this study was to measure the tightness of two different types of horizontal air curtain: a one-sided horizontal air curtain and a two-sided horizontal air curtain. The tightness of an air curtain is defined as the ability to reduce infiltration in comparison to an unprotected door. The momentum of the jet along the nozzle was kept constant. In both air curtain types the width of the nozzle was 10 mm, which is a typical value in factory-made air curtains. The blowing angle and the jet velocity were changed to find the maximum tightness value. Measurements were done in the doorway (height 2.0 m, width 1.8 m) of a laboratory hall (height 8.3 m, volume 453 m3). The tightness of the air curtain was measured with a concentration decay method using a gas analyzer and nitrous oxide tracer gas. The mixing fan was kept on during the whole measurement to maintain complete mixing of the tracer gas and to reduce stratification of the indoor temperature. Altogether, 27 tests were carried out, the measuring time being 10 min per test. The indoor temperature at the beginning of the each test was 21°C, the outdoor temperature varied between 0°C and -20°C. With the two-sided air curtain the maximum tightness was only 44%. With the one-sided air curtain the highest tightness value measured, was 57%. Both these values are lower than expected having a strong effect on the payback time calculations and thermal conditions near the doorway.
C. Figueroa, University of North Alabama, Florence, AL.
Industrial ventilation is regularly included in occupational health and safety academic curricula, either as a course component or as an exclusive subject. The importance of this topic is clear; a recent survey showed that more than 75% of employers responding to a survey on the expectations of knowledge and skills of masters-trained industrial hygienists rated ventilation principles and practice as essential. Less clear is our knowledge of the breadth and depth coverage of this subject in academia. A survey study is conducted to shed light on the pedagogical approach to this subject as well as the ways and means used in this educational pursuit. The survey is limited to courses offered as a required or elective component of the curriculum either at the undergraduate or graduate level. Academic programs in occupational health and safety, industrial hygiene, industrial safety, or a similar denomination are identified by using listings of the AIHA, ASSE, ABET, or NIOSH. Those programs with offerings in industrial ventilation are contacted with a request to complete an electronic questionnaire. The questionnaire is designed to characterize objectives, structure, unit components, teaching methods, characteristics of target audience, and technical and instrumental support of the course offerings. This study also aims to identify novel approaches to the subject, emerging areas of educational needs, and the use of nontraditional approaches to the subject. Identified new developments and general trends may serve, respectively, as guidance in updating cycles and as benchmark for evaluating completeness and/or relevance of course contents.
H. Goodfellow, Techint Goodfellow Technologies Inc., Mississauga, ON, Canada; E. Tähti, Vantaa Energy Ltd., Vantaa, Finland; J. Stachulak, INCO, Sudbury, ON, Canada.
This paper will outline the recent progress on the ventilation science technology field based on more than 50 million dollars of research and development in the industrial ventilation field. Current air quality issues (i.e., diesel exhaust emissions, heat stress, etc.) in mine ventilation will be outlined. Specific examples will be given of possible areas of technology transfer and future areas of cooperation between the industrial ventilation and mine ventilation communities.
Posted May 30, 2006