Design and evaluation of a portable negative pressure hood with HEPA filtration to protect health care workers treating patients with transmissible respiratory infections

Background: To mitigate potential exposure of healthcare workers (HCWs) to SARS-CoV-2 via aerosol routes, we have developed a portable hood which not only creates a barrier between HCW and patient, but also utilizes negative pressure with filtration of aerosols by a high-efficiency particulate air filter. Material and Methods: The hood has iris-port openings for access to the patient, and an opening large enough for a patient's head and upper torso. The top of the hood is a high-efficiency particulate air filter connected to a blower to apply negative pressure. We determined the aerosol penetration from outside to inside in laboratory experiments. Results: The penetration of particles from within the hood to the breathing zones of HCWs outside the hood was near 10^-4 (0.01%) in the 200-400 nm size range, and near 10⁻³ (0.1%) for smaller particles. Penetration values for particles in the 500 nm-5 μm range were below 10⁻² (1%). Fluorometric analysis of deposited fluorescein particles on the personal protective equipment of an HCW revealed that negative pressure reduces particle deposition both outside and inside the hood. Conclusions: We find that negative pressure hoods can be effective controls to mitigate aerosol exposure to HCWs, while simultaneously allowing access to patients.