Source Control with Masks and Respirators in Hospitals: Exhalation Aerosol Shedding, Jet Suppression, and Near-/Far-Field Persistence

Details

• Journal Article:
  Journal of Hospital Infection
• Personal Author:
  Yang, W. ; Myers, W. R. ; Ryan, K. J. ; Zheng, L. ; Zhang, Y. ; Li, X.
• Description:
  Background: Infectious exhalation aerosol source control using masks and respirators in hospitals depends on the aerosol shedding and its dispersion. Methods: In a simulation study with a headform, we used a leakage testing system for total outward leakage (TOL) and count median diameter (CMD) and a separate hood for horizontal exhalation-jet velocity at 1, 2, and 3 ft (0.30, 0.61, 0.91 m). Neutralised NaCl aerosols were generated to mimic human exhalation shedding. Five devices for source control - surgical mask (SM), non-valved N95 filtering facepiece respirator (N95 FFR), valved N95 (FFRV), elastomeric half-mask respirator (EHMR), and EHMR with an SM overlay (EHMRSM) - were tested under three faceseal conditions (0%, 50%, and 100%) and three flow rates (17, 28, 39 L min-1). We derived a near-field (NF) emission index and a far-field (FF) persistence index. Results: Device type significantly affected TOL and CMD (P < 0.01). The N95 FFR minimised TOL (approx. equal to 5-9%) and eliminated horizontal jets, yielding near-zero NF and the lowest FF. The EHMR had the highest TOL (approx. equal to 82-88%) and persistent jets, producing the largest NF and FF; FFRV was intermediate. The SM and EHMRSM collapsed jets (NF approx. equal to 0) but retained moderate to high TOL, sustaining elevated FF. Leaked particles were predominantly submicron (CMD approx. equal to 0.42-0.61 µm). Conclusions: Gravitational loss (approx. equal to 0.02-0.05 h-1) is negligible compared with clinical ventilation to clean leaked aerosols, yielding orders of magnitude longer clearance times, so settling alone cannot deliver timely clearance. In practice, low-leakage devices - preferably non-valved N95s - should be paired with adequate air-change rates. Description provided by NIOSH
• Subjects:
  • Hospitals
  • Health Personnel
  • Occupational Health
  • Personal Protective Equipment
  • Safety
  • Ventilation
• Keywords:
  • Infectious diseases; Health care facilities; Personal protective equipment; PPE; Aerosols; Surgical masks; N95 filtering facepiece respirators; Elastomeric half-mask respirators; Ventilation; Hospital equipment;
  • Author Keywords: Source control; Elastomeric half-mask respirator; EHMR; N95 filtering facepiece respirator; Surgical mask; Near-field; Far-field; Total outward leakage; TOL; Ventilation
• Source:
  J Hosp Infect 2026 Apr; 170:236-245
• ISSN:
  0195-6701
• Document Type:
  Text
• Funding:
  Contract
• Genre:
  Journal Article
• Place as Subject:
  Philadelphia Region OSHA ; West Virginia
• CIO:
  National Institute for Occupational Safety and Health (NIOSH)
• Topic:
  Workplace Safety & Health
• Location:
  North America
• Pages in Document:
  10 pdf pages
• Volume:
  170
• NIOSHTIC Number:
  nn:20071634
• Contact Point Address:
  W. Yang, No.1, Daxue Road, Xuzhou, Jiangsu, 221116, China
• Email:
  weihua.yang@cumt.edu.cn
• Federal Fiscal Year:
  2026
• Peer Reviewed:
  True
• Download URL:
  https://stacks.cdc.gov/view/cdc/259409/cdc_259409_DS1.pdf
• File Type:
  [PDF - 2.76 MB]
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:254fbfe7b36f1b68f789af269f08fc499651912198aeed808ab33b7f085b1c9bbbc7cfdc33f98f9181cd7f904b15a21ff86646440d98c0fae1a17ebec6fe2772