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NIOSH Activities: Engineering Infection Controls

Controlling exposures to workplace hazards is a key method of protecting workers. Engineering controls are high on the hierarchy of controls used to protect workers from workplace hazards. Engineering controls remove or reduce a hazard, or they place a barrier between the worker and the hazard. Well-designed engineering controls are preferred to personal protective equipment (PPE) because engineering controls can be highly effective in protecting workers, and they generally place less of the burden upon worker actions. NIOSH researchers are involved in the following research efforts focused on developing and evaluating engineering controls to reduce the spread of infectious disease in healthcare settings.

NIOSH Engineering Control Research on Infection Control

General Description: Public reports suggest the U.S. healthcare system does not have enough capacity to isolate patients during a large airborne infectious disease epidemic or bioterrorism event. Government response recommendations mention portable filtration units and other engineering controls needed to isolate surge patients. Little information is available to help with selecting these engineering controls or beginning their use. Also largely unknown is their ability to provide the needed protection. This research activity used off-the-shelf materials to construct prototype expedient airborne infection isolation areas within healthcare facilities. Isolation performance testing involved the generation of an airborne droplet nuclei aerosol to represent infectious aerosols. Concentration monitoring of the aerosol in key locations showed airflow patterns, airborne concentrations, and overall levels of isolation. The research identified what is needed to set up and use expedient isolation areas to control exposures to infectious aerosol, it calculates the expected performance of the measures, and it gives guidance for developing and using the areas to meet requirements for isolating airborne infections during surge events.

Relevance to worker safety and health: Research findings show that these expedient isolation areas effectively stop infectious aerosols from migrating throughout the patient area. Some configurations also significantly protect areas at the patient’s bedside. Reducing the spread of infectious aerosols is especially important for infectious diseases that are thought to be infectious through the air over short or long distances, or by droplet, surface contact, and fomite transmission. Findings from this research can be used by government or private organizations and healthcare facilities to develop emergency response guidance options to control exposures to infectious aerosols. Results from this study have already been used in some guidance documents outside of NIOSH, and have led to the development of similar engineering controls for non-traditional healthcare settings.

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

Status: Research funding ended September 2010 however related dissemination efforts continue to occur. Along with the published papers listed above, additional research translation publications may be developed as needs and opportunities arise.

Point of Contact: CDC-Info

General Description: This research builds on the CDC work to develop designs for expedient (or surge) isolation areas to control infectious aerosols, which were developed for traditional hospital environments. This work applies the same control concepts to emergency medical shelters and other non-traditional healthcare environments. Early research showed these techniques could be successful within a variety of healthcare facilities across the United States. Subsequent work translated these proven engineering control techniques for configurations applicable to non-traditional healthcare environments where great masses of patients are treated, such as that used following a mass-casualty event. A research strategy employed during this effort was to use training events to make these types of protective interventions more familiar to responders and planners. Training events also identify complications that could happen when using the interventions on a large scale, before actually using them in a real emergency. The effort continues to help emergency response officials and their funding authorities to be more familiar with these engineering control interventions, which have a low cost and are effective at reducing exposures.

Relevance to Worker Safety and Health: This project uses research on expedient isolation areas to control exposures to infectious aerosols within healthcare environments. The project translates this research for a nontraditional “infectious” mass casualty environment. Examples of these environments would include setting up cafeterias, gymnasiums, or other shelters to treat large numbers of patients with infectious diseases. This work helps responders be more familiar with control concepts, and the research will report on containing aerosols and reducing healthcare worker exposures in a mass-casualty environment.

Key Findings: NIOSH researchers developed two prototype designs that apply to emergency medical shelter environments. NIOSH has filed CDC employee invention reports with the CDC’s Technology Transfer Office. The CDC does not plan to patent either invention. One of the two prototype designs can be ordered commercially. The second design, a mobile platform with built-in fan/filter/back-up power options, has been tested and its performance verified, but it is not yet available commercially.

Status: This research activity has ended, however the effort to translate the results and associated information continues. This will include developing peer-reviewed and instructional literature, as well as a commercially available designs for expedient isolation areas to control airborne infection. NIOSH is developing a publication on “Expedient Airborne Isolation” to help with rapidly distributing the instructional how-to literature if an airborne epidemic emergency happens. Although potential manufacturing partners have been identified, developing commercial availability options for the mobile platform is on hold, pending more research funding or a triggering event that causes sudden need.

Point of Contact: CDC-Info

General Description: New research at NIOSH focuses on ambulances and their ventilation design, engineering controls, and decontamination. The research seeks to make emergency workers inside ambulances less likely to be exposed to infectious diseases. The research has three parts: (1) evaluating ventilation patterns within the ambulance via surrogate tracer techniques and subsequently identifying ventilation designs and interventions that reduce occupant exposure and airborne contaminant dispersion; (2) building a computational fluid dynamics model of the ambulance interior environment and using this model to improve ventilation design and find how contaminants disperse; and (3) transferring recently proven ultraviolet germicidal irradiation (UVGI) technology into the smaller-scale interior ambulance environment, verifying that it is effective within that environment, and giving guidance on how to operate the technology when implementing it. This technology uses portable “Total Room and Air” units that use UVGI energy sources to decontaminate air and surfaces in a healthcare treatment environment which in this case, is the ambulance patient module.

Relevance to Worker Safety and Health: This research studied airflow patterns within a common government-specification ambulance module and evaluated whether these patterns expose emergency response workers to contamination from patients. Researchers then used these findings to identify engineering control interventions to reduce the workplace exposure risk to airborne infectious contaminants. The intervention’s intent was to reduce the degree and spread of surface contamination throughout the module and driver’s cab. The second phase studied how well ultraviolet germicidal irradiation works as an adjunct engineering control to reduce surface contamination as an exposure risk within the patient module.

Key Findings: The baseline computational fluid dynamics model has been completed, confirming the qualitative test findings regarding the chance for EMT exposure to aerosol from patients within the ambulance module.  The research on UVGI surface decontamination has demonstrated that UVGI systems can be an effective adjunct surface cleaning method to reduce potential infectious exposures to healthcare workers and patients within the ambulance patient module.

Status: The first-generation ventilation intervention design is complete and has been installed and tested. Although the prototype’s high-efficiency filtration improved indoor contamination levels, the worker-protective directional airflows were not sufficiently established and will be the focus of future research. The ventilation research was subsequently put on hold until completing the ultraviolet germicidal irradiation disinfection research. Baseline ultraviolet germicidal irradiation energy distribution tests upon the ambulance module surfaces have been completed and became the basis for follow-on research. To date, the ultraviolet germicidal irradiation research has developed two prototype systems: (1) an ultraviolet germicidal radiation tripod to temporarily place in a stationary, unoccupied ambulance to disinfect surfaces, and (2) a built-in ultraviolet germicidal irradiation light package that can disinfect unoccupied ambulance module interiors, whether stationary or mobile. Energy dispersion measurements as well as surrogate “bug” kill efficiency testing for both prototypes was recently completed.  Initial reporting of the ultraviolet germicidal irradiation data  is anticipated in late 2017/early 2018 with additional dissemination to follow.

Ambulance Disinfection using Ultraviolet Germicidal Irradiation (UVGI): Effects of Fixture Location and Surface Reflectivity, accepted for publication in the Journal of Occupational & Environmental Hygiene

Point of Contact: CDC-Info

General Description: Traditional engineering guidance for designing airborne infection isolation rooms (AIIR) seeks to protect the rest of the hospital by keeping infectious aerosol from migrating by air. Various authorities specify AIIR as an engineering control for healthcare workers. This research uses computational fluid dynamic (CFD) computer models to study several worker-exposure scenarios within AIIR and traditional patient rooms. These scenarios include: (1) comparing a bedside healthcare worker’s risk of being exposed through the air in an existing AIIR to a traditional patient room from the same hospital, (2) comparing a bedside healthcare worker’s exposure in a traditional patient room under scenarios with and without the exposure protection of an expedient airborne infection isolation intervention, and (3) comparing a bedside healthcare worker’s exposure in an AIIR as traditionally designed to exposures predicted using a newly-proposed AIIR design that incorporates local source control and directional airflows to protect room occupants. The goal is to measure the chance of exposure within each room scenario and to identify areas for future research. Subsequently, design recommendations will be identified and modeled to reduce chances of exposure within the AIIR.

Relevance to Worker Safety and Health: Engineering controls within AIIRs may not adequately protect the healthcare workers within them against exposure to infectious aerosols. This research seeks to demonstrate the exposure risks that exist to healthcare workers under various healthcare scenarios and to reduce the frequency with which traditional AIIRs are incorrectly prescribed to control exposures to infectious aerosols. The research also identifies airflow-specific design parameters within the AIIR that actually give better workplace protection from such exposures.

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

Status: Funding for this research effort has expired and the CFD model development and analysis has concluded.  One additional publication is anticipated in late 2017.  Based upon these successful research results, future research validating the protective design benefits of the alternate AIIR ventilation configuration within a full-scale mock-AIIR may be proposed.  This is believed to be a necessary step to facilitate research translation into the healthcare design community.

Point of Contact: CDC-Info

Page last reviewed: March 28, 2018