Dust Control Handbook for Industrial Minerals Mining and Processing

CHAPTER 9: OPERATOR BOOTHS, CONTROL ROOMS,AND ENCLOSED CABSOperator booths, control rooms, and enclosed cabs have all been used for many years to isolateworkers from dust sources in mineral processing operations. When they are properly designed,installed, and maintained, they can provide a safe work environment that supplies clean andacceptable air quality to the worker. There has been a substantial amount of research performedin this area over the past decade identifying and correcting problematic issues and determiningthe critical components that are necessary for an effective system.Workers in operator booths, control rooms, and enclosed cabs at mining operations aresurrounded by dynamic working conditions that have highly variable dust sources. Theseenclosures create a microenvironment for the workers where they can be either more protected ormore vulnerable to respirable dusts. Workers can be more vulnerable to in-cab dust sources(floor heaters, dirt on floors/walls, or on operator's clothing, etc.) that are trapped within theenclosure. Enclosed cabs on mobile equipment are actually harder to control and maintain thanenclosed stationary areas (operator booths and control rooms) since the moving of the equipmentconstantly stresses and can compromise the integrity of the enclosure.Figure 9.1 shows a general design of a filtration and pressurization system. At mineralprocessing operations, filtration and pressurization systems are the primary engineering controlto reduce worker exposure to airborne dust in operator booths, control rooms, and enclosed cabs.These enclosures should have an effective filtration system that cleans both outside and inside airthat is brought into the enclosure and sufficient enclosure integrity in order to achievepressurization. The most effective filtration and pressurization systems are integrated into theheating, ventilating, and air-conditioning (HVAC) units. A substantial amount of research hasbeen performed to improve the air quality in enclosed cabs of surface mining equipment, and thisresearch is directly applicable to operator booths and control room dust control systems.EFFECTIVENESS TERMINOLOGYWhen evaluating a pressurization and filtration system—comparing outside with insiderespirable dust concentrations—a number of different descriptors can be used to provide anumerical value that ranks the system's effectiveness. The following three descriptors arecommonly used for this purpose:CoProtection Factor (PF) = ; (ratio)CiEfficiency (η) =CoCoCi; (fraction, or multiplied by 100 for percent value)Penetration (Pen) = 1 – η; (fraction)Operator Booths, Control Rooms, and Enclosed Cabs 225