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NIOSH Activities: Engineering Infection Controls

Controlling exposures to occupational hazards is the fundamental method of protecting workers. Engineering controls, which are high on the hierarchy of controls, are used to remove/reduce a hazard or place a barrier between the worker and the hazard. Well-designed engineering controls are typically preferred over personal protective equipment (PPE) since they can be highly effective in protecting workers and generally place less of the protective burden upon worker actions in order to provide this high level of protection. NIOSH researchers are involved in the following research efforts, focused on the development and evaluation of engineering controls to reduce infectious disease transmission potential within occupational healthcare settings.

Expedient Airborne Infectious Isolation Within Traditional Hospital Environments

General Description: Public reports indicate that the U.S. healthcare system lacks the patient isolation capacity to handle a large airborne infectious epidemic or bioterrorism event. Government response recommendations include references to portable filtration units and other engineering controls for surge patient isolation requirements yet minimal guidance is available to instruct on their selection or implementation and their occupational-protective capacity is predominantly unknown. This research activity uses off-the-shelf materials to construct prototype expedient airborne infectious isolation (AII) areas within healthcare facilities. Isolation performance testing involved the generation of airborne droplet nuclei to represent infectious aerosol generation. Concentration monitoring of the aerosol at key locations identified airflow patterns, airborne concentrations and overall levels of isolation. Implementation parameters necessary for effective expedient AII are identified, their expected performance quantified, and guidance recommendations developed for their emergency implementation to meet surge airborne infectious isolation requirements.

Relevance to worker safety and health: Research findings demonstrate that not only can these expedient AII configurations effectively prevent airborne migration throughout the patient area, some configurations also provided significant protection directly at the patient bedside. This has significant importance for those infectious diseases thought only to be airborne infectious over short range distances. Findings from this research can be used by government/private entities and healthcare facilities to develop emergency response guidance options for expedient airborne infectious isolation. Results from this study have already been incorporated into some external guidance documents and have fueled development of similar engineering controls for non-traditional healthcare settings.

Key Findings: Key findings of this research are found in the following publications:

Status: Funding ended September 2010. In addition to the published papers listed above under "Key Findings", one additional peer-reviewed manuscript is under development and not yet submitted for publication.

Point of Contact: NIOSH-INFO

Airborne Infectious Isolation Within Emergency Shelters and Non-traditional Healthcare Environments

General Description: This research activity modifies prior CDC research efforts to develop expedient (or surge) airborne infectious isolation (AII) designs developed for traditional hospital environments and applies the control concepts to emergency medical shelter and other non-traditional healthcare environments. Existing research has demonstrated the success potential of these techniques within a variety of healthcare facilities across the country. Current efforts will translate the proven engineering control intervention techniques into mass-patient configurations such as those found at a mass-casualty training event. The goal is to improve responder and planner familiarity with these types of protective interventions and to identify potential unknown complications, associated with large-scale implementation, prior to their actual use in a real emergency. Lastly, this effort continues to familiarize emergency response officials, and their funding authorities, with the low-cost, exposure-reducing effectiveness of these engineering control interventions.

Relevance to Worker Safety and Health: This project translates knowledge learned from prior research on expedient isolation within healthcare environments to a non-traditional "infectious" mass casualty environment such as that which might be established in a cafeteria, gymnasium, or other shelter. In addition to increasing responder familiarity with these specific control concepts, the research demonstrates and will report upon the aerosol containment and reductions in healthcare worker exposures in a mass-casualty environment.

Key Findings: Two expedient airborne isolation (EAI) prototype designs, applicable to emergency medical shelter environments, have been developed and CDC employee invention reports filed with the CDC’s Technology Transfer Office. There is no plan to patent either design. One of the two prototype designs is currently available commercially for order. The second design, a mobile platform with built-in fan/filter/back-up power options, has been tested and performance verified but is not commercially available.

Status: Though funding for this two-year research activity ended in September 2010, the information translation effort continues, and will include development of peer reviewed and instructional literature, as well as a commercially-available expedient AII engineering control. An Expedient Airborne Isolation Topic Page is under development to aide rapid dissemination of the instructional how-to literature in the event of an airborne epidemic emergency. Development of commercial availability options for the mobile EAI platform is on hold, pending identification of additional research funding. 

Point of Contact: NIOSH-INFO

Engineering Controls for Infection Control Within Ambulance Patient Modules

General Description: The work on ambulance ventilation design, engineering controls and decontamination is new research within NIOSH with an overall goal of minimizing the ambulance environment as a source of infectious exposure potential for emergency medical personnel. Within itself, this research has three components (1) Evaluation of ventilation patterns within the ambulance via surrogate tracer techniques and subsequent identification of ventilation designs and interventions that reduce occupant exposure and airborne contaminant dispersion, (2) Build and validate a Computational Fluid Dynamics (CFD) model of the ambulance interior environment and use this model to optimize ventilation design factors and identify contaminant dispersion tendencies, (3) Transfer recently proven technology that used portable Ultraviolet Germicidal Irradiation (UVGI) "Total Room and Air" decontamination units for air and surface decontamination within a healthcare treatment environment into the smaller-scale interior ambulance environment, verify its effectiveness within that environment and provide operating guidance for its implementation.

Relevance to Worker Safety and Health: This research will qualitatively and quantitatively evaluate airflow patterns within a common government-specification ambulance module and evaluate the potential for these patterns to expose emergency response personnel to patient source contaminant. Based upon these findings, engineering control interventions will be identified to reduce the occupational exposure risk to airborne infectious contaminants, while simultaneously attempting to reduce the degree and spread of surface contamination throughout the module and driver’s cab. The second phase of this effort will evaluate the potential decontamination efficacy of ultraviolet germicidal radiation (UVGI) as a between-patient control to reduce surface contamination as an exposure risk within the patient module.

Key Findings: The baseline CFD model has been finalized, confirming the potential for EMT exposure to patient-source aerosol within the ambulance module.

Status:The ventilation intervention design is underway and will be modeled/installed/and tested during FY 2013. Baseline UVGI energy distribution tests upon the ambulance module surfaces were completed in late FY2012. Data analysis and reporting of the UVGI data are targeted for completion during the first half of FY2013.

Point of Contact: NIOSH-INFO

Study and Optimization of Airflow Design Patterns Within Hospital Airborne Infectious Isolation Rooms

General Description: Traditional engineering design guidance for airborne infectious isolation rooms (AIIR) is intended to protect the rest of the hospital from airborne migration of infectious aerosol yet the AIIR is often specified by various authorities as a form of occupational engineering control for healthcare workers. This research seeks to use computational fluid dynamic evaluations to compare a bedside healthcare worker’s airborne exposure potential in an existing AIIR to such a worker’s airborne exposure potential in a traditional patient room from the same hospital. The aim is to provide a quantitative comparison of the exposure potential within each room. Subsequently, design recommendations will be identified and modeled in an effort to reduce the exposure potential within the AIIR.

Relevance to Worker Safety and Health: Healthcare workers who must enter AIIRs are believed to receive minimal protection form airborne exposure while within these rooms. This research seeks to reduce the frequency of incorrectly prescribing traditional AIIRs as a form of engineering control for airborne infectious exposures and to identify airflow specific design parameters within the AIIR that actually provide some form of occupational protection from such exposures.

Key Findings: The initial CFD research findings for this effort were presented at the Jan 2012 Winter Meeting of the American Society of Heating Refrigeration and Air Conditioning Engineers (ASHRAE). A peer-reviewed manuscript, Assessment of health-care worker exposure to pandemic flu in hospital rooms. Ghia, U., S. Konangi, et. al., was published in the ASHRAE Trans 2012 Jan; 118 (Part 1):442-449.  View the NIOSHTIC-2 citation  .

Status: Although funding for this research effort has expired, a follow-up CFD research contract, investigating the potential protective benefit of applying expedient isolation interventions within traditional patient rooms is still underway and expected to conclude in FY2013.

Point of Contact: NIOSH-INFO