An Ion Generator for Neutralizing Concentrated Aerosols

Details

• Personal Author:
  Hinds WC ; Kennedy NJ
• Description:
  An ion generator was developed to neutralize concentrated streams of large, highly charged particles in a low-velocity wind tunnel. The aerosol stream tested consisted of 30 mu m aluminum oxide particles (aerodynamic diameter 52 mu m) at a flow rate of 9.6 m3/h (160 L min) and a mass concentration of 43 g/m3. The average number of excess charges per particle was 240,000 (positive), which corresponds to a neutralizing current requirement of 0.11 mu A. Neutralization to < +/- 10,000 charges per particle was necessary to prevent electrostatic sampling artifacts. Neutralization with radioactive sources would have required an impractically large source. The ion generator, constructed from 21 and 32 mm PVC pipe, has 4 peripheral radial electrodes of 0.5 mm tungsten wire and a 2.0 mm diameter central electrode. The aerosol flowed through the ion generator along its axis. The ion generator was powered by an adjustable (0-8.5 kV) power supply. Performance of the ion generator was monitored with an isokinetic Faraday-cup sampler connected to a Keithley Model 6512 electrometer capable of 0.1 fA resolution. The sampler used a stainless steel 47 mm filter holder as the Faraday cup. The cup was insulated with Teflon inside a 90 mm diameter stainless steel enclosure with a 21 mm diameter inlet. This setup gave near real-time measurement of the charge state of the aerosol in the wind tunnel. By adjusting the ion generator power supply, particle charge could be reduced to < 2% of its original charge. Ion generator output was sufficiently stable to maintain the particle charge within +/- 2% of the original charge over a 1 h period. These reduced charge levels are comparable to charge levels found on workplace aerosols. [Description provided by NIOSH]
• Subjects:
  Aerosols Aluminum Compounds Aluminum Oxide Occupational Health Safety
• Keywords:
  Aerosol Particles Aluminum Oxide Electrical Charge Electrostatic Fields Ionization Particle Aerodynamics
• ISSN:
  0278-6826
• Document Type:
  Text
• Funding:
  Grant
• Genre:
  Journal Article
• Place as Subject:
  California ; OSHA Region 9
• CIO:
  National Institute for Occupational Safety and Health (NIOSH)
• Topic:
  Workplace Safety & Health
• Location:
  North America
• Pages in Document:
  214-220
• Volume:
  32
• Issue:
  3
• NIOSHTIC Number:
  nn:20057863
• Citation:
  Aerosol Sci Technol 2000 Mar; 32(3):214-220
• CAS Registry Number:
  Alumina (CAS RN 1344-28-1)
• Federal Fiscal Year:
  2000
• Performing Organization:
  Department of Environmental Health Sciences, UCLA School of Public Health, Los Angeles, California
• Peer Reviewed:
  True
• Start Date:
  19940930
• Source Full Name:
  Aerosol Science and Technology
• End Date:
  19980929
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:ac15b7af631635c8290f34e495e865d3934da17170cefca48d4e8d930fed65e8d77471eb1d9da93becdc7d7f195ed75e3e54cb9d1cfc6d55ae09623aa0f31da4
• Download URL:
  https://stacks.cdc.gov/view/cdc/215069/cdc_215069_DS1.pdf
• File Type:
  [PDF - 324.98 KB ]