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Aerosol generation by blower motors as a bias in assessing aerosol penetration into cabin filtration systems.
Heitbrink WA; Collingwood S
J Occup Environ Hyg 2005 Jan; 2(1):45-53
In cabin filtration systems, blower motors pressurize a vehicle cabin with clean filtered air and recirculate air through an air-conditioning evaporator coil and a heater core. The exposure reduction offered by these cabins is evaluated by optical particle counters that measure size-dependent aerosol concentration inside and outside the cabin. The ratio of the inside-to-outside concentration is termed penetration. Blower motors use stationary carbon brushes to transmit an electrical current through a rotating armature that abrades the carbon brushes. This creates airborne dust that may affect experimental evaluations of aerosol penetration. To evaluate the magnitude of these dust emissions, blower motors were placed in a test chamber and operated at 12 and 13.5 volts DC. A vacuum cleaner drew 76 m3/hour (45 cfm) of air through HEPA filters, the test chamber, and through a 5 cm diameter pipe by a vacuum cleaner. An optical particle counter drew air through an isokinetic sampling probe and measured the size-dependent particle concentrations from 0.3 to 15 microm. The concentration of blower motor aerosol was between 2×10(5)and 1.8×10(6)particles/m3. Aerosol penetration into three stationary vehicles, two pesticide application vehicles and one tractor, were measured at two conditions: low concentration (outside in the winter) and high concentration (inside repair shops and burning incense sticks used as a supplemental aerosol source). For particles smaller than 1microm, the in-cabin concentrations can be explained by the blower motor emissions. For particles larger than 1µm, other aerosol sources, such as resuspended dirt, are present. Aerosol generated by the operation of the blower motor and by other sources can bias the exposure reduction measured by optical particle counters.
Aerosol-generators; Aerosol-particles; Aerosols; Filtration; Particle-counters; Airborne-dusts; Air-treatment-equipment; Air-contamination; Engineering-controls; Particulate-dust; Particulates; Measurement-equipment; Quality-control; Occupational-exposure; Author Keywords: aerosol generated; bias; cabin filtration; carbon brushes
The University of Iowa, The College of Public Health, Department of Occupational and Environmental Health, 100 Oakdale Campus - 108 IREH, Iowa City, IA 52241
Grant-Number-T42-CCT-717547; Grant-Number-T42-OH-008414; Grant-Number-T42-OH-008491
Issue of Publication
Journal of Occupational and Environmental Hygiene
The University of Iowa, Iowa City, Iowa
Page last reviewed: September 2, 2020
Content source: National Institute for Occupational Safety and Health Education and Information Division