Negative Pressure Isolation Rooms Research Articles

Concentration Profiles of AirborneMycobacterium tuberculosisin a Hospital

Pulmonary tuberculosis remains one of the major public health issues worldwide. However, concentration profiles of airborne Mycobacterium tuberculosis in hospitals and other medical facilities have not been well characterized. Therefore, the aim of the present study was to measure concentration profiles of airborne M. tuberculosis in a hospital including TB-patient related areas (TB-areas), and non-TB-patient related areas (non-TB-areas). A total of 58 airborne samples were collected by a filter and quantified by real-time qPCR system. It was found that the airborne M. tuberculosis concentrations in TB-areas were significantly higher than those in non-TB-areas. In regard to the profiles in the investigated hospital, the airborne M. tuberculosis concentrations from high to low were found in the waiting rooms and consulting rooms of medical department, emergency department, medical wards, main registry area, waiting rooms of ophthalmology department, and dining hall, respectively. In the medical wards area, it was found that the airborne M. tuberculosis concentrations in the room of a suspected TB patient were even higher than those found in negative pressure isolation rooms with TB patient. This suspected TB patient was, in fact, diagnosed as a TB patient a month later. In conclusion, concentration profiles of airborne M. tuberculosis in hospital environments were successfully characterized in our present study. In addition, it was strongly demonstrated that TB-areas do have higher airborne M. tuberculosis concentrations than non-TB-areas and implicate higher risks for nosocomial TB infection. Moreover, environmental monitoring of airborne M. tuberculosis might provide an early indicator for identification of TB patient.

A survey of tuberculosis services in the UK

Aim:To determine the provision of services for children with tuberculosis (TB) living in the UK.Method:A postal questionnaire was sent to the most appropriate paediatrician and adult physician in every acute...

Hospital and community acquired infection and the built environment--design and testing of infection control rooms.

Negative-pressure isolation rooms are required to house patients infected with agents transmissible by the aerosol route in order to minimise exposure of healthcare workers and other patients. Housing patients in a separate room provides a barrier which minimises any physical contact with other patients. An isolation room held at negative pressure to reduce aerosol escape and a high air-change rate to allow rapid removal of aerosols can eliminate transmission of infectious aerosols to those outside the room. However, badly designed and/or incorrectly operating isolation rooms have been shown to place healthcare workers and other patients at risk from airborne diseases such as tuberculosis. Few standards are available for the design of isolation rooms and no pressure differential or air-change rates are specified. Techniques such as aerosol particle tracer sampling and computational fluid dynamics can be applied to study the performance of negative-pressure rooms and to assess how design variables can affect their performance. This should allow cost-effective designs for isolation rooms to be developed. Healthcare staff should be trained to understand how these rooms operate and there should be systems in place to ensure they are functioning correctly.

Natural Ventilation for the Prevention of Airborne Contagion

BackgroundInstitutional transmission of airborne infections such as tuberculosis (TB) is an important public health problem, especially in resource-limited settings where protective measures such as negative-pressure isolation rooms are difficult to implement. Natural ventilation may offer a low-cost alternative. Our objective was to investigate the rates, determinants, and effects of natural ventilation in health care settings.Methods and FindingsThe study was carried out in eight hospitals in Lima, Peru; five were hospitals of “old-fashioned” design built pre-1950, and three of “modern” design, built 1970–1990. In these hospitals 70 naturally ventilated clinical rooms where infectious patients are likely to be encountered were studied. These included respiratory isolation rooms, TB wards, respiratory wards, general medical wards, outpatient consulting rooms, waiting rooms, and emergency departments. These rooms were compared with 12 mechanically ventilated negative-pressure respiratory isolation rooms built post-2000. Ventilation was measured using a carbon dioxide tracer gas technique in 368 experiments. Architectural and environmental variables were measured. For each experiment, infection risk was estimated for TB exposure using the Wells-Riley model of airborne infection. We found that opening windows and doors provided median ventilation of 28 air changes/hour (ACH), more than double that of mechanically ventilated negative-pressure rooms ventilated at the 12 ACH recommended for high-risk areas, and 18 times that with windows and doors closed (p < 0.001). Facilities built more than 50 years ago, characterised by large windows and high ceilings, had greater ventilation than modern naturally ventilated rooms (40 versus 17 ACH; p < 0.001). Even within the lowest quartile of wind speeds, natural ventilation exceeded mechanical (p < 0.001). The Wells-Riley airborne infection model predicted that in mechanically ventilated rooms 39% of susceptible individuals would become infected following 24 h of exposure to untreated TB patients of infectiousness characterised in a well-documented outbreak. This infection rate compared with 33% in modern and 11% in pre-1950 naturally ventilated facilities with windows and doors open.ConclusionsOpening windows and doors maximises natural ventilation so that the risk of airborne contagion is much lower than with costly, maintenance-requiring mechanical ventilation systems. Old-fashioned clinical areas with high ceilings and large windows provide greatest protection. Natural ventilation costs little and is maintenance free, and is particularly suited to limited-resource settings and tropical climates, where the burden of TB and institutional TB transmission is highest. In settings where respiratory isolation is difficult and climate permits, windows and doors should be opened to reduce the risk of airborne contagion.

On the Need for a Separate Standard for Performance Testing of Negative-Pressure Isolation Rooms

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Door-opening motion can potentially lead to a transient breakdown in negative-pressure isolation conditions: the importance of vorticity and buoyancy airflows

SummaryA patient with severe chickenpox was admitted to a negative-pressure isolation room. He remained sedated, intubated and mechanically ventilated throughout his admission. He was managed only by nurses immune to chickenpox. A non-immune male nurse occasionally handed equipment through the doorway, without entering the room. Ten days later, he also developed chickenpox. Sequencing of viruses from the patient and nurse showed the same rare genotype, indicating nosocomial transmission. An experimental model demonstrated that, despite negative pressure, opening the door could have resulted in transport of infectious air out of the isolation room, leading to a breakdown in isolation conditions.

The Influence of Air Motion on Bacteria Removal in Negative Pressure Isolation Rooms

Controlling the concentration of bacteria in patient rooms to prevent airborne infection is one of the important issues in infection control in hospitals. The effects of air inlet/outlet locations, patient styles of reclining, and air change rate on bacteria removal have been studied. A real hospital isolation room was the object for computation and experiment. In computation, commercial CFD software was used to simulate steady and transient air motion. The flow model was incompressible turbulent flow including buoyancy effect. In the experiment, we used fog generated by an ultrasonic nebulizer to put experimental bacteria into the patient room, and then examined the effect of bacteria removal by means of colony counts. Both computational and experimental results showed that the original design of the isolation room could not remove bacteria effectively. The air inlet/outlet locations were rearranged and the computations and experiments were redone to find better designs. Results of the present study revealed that a large air change rate might not be necessary for most cases. Finally, a set of air inlet/outlet locations and the associated air change rate were suggested.

Using an integrated infection control strategy during outbreak control to minimize nosocomial infection of severe acute respiratory syndrome among healthcare workers

SummaryHealthcare workers (HCWs) are at risk of acquiring severe acute respiratory syndrome (SARS) while caring for SARS patients. Personal protective equipment and negative pressure isolation rooms (NPIRs) have not been completely successful in protecting HCWs. We introduced an innovative, integrated infection control strategy involving triaging patients using barriers, zones of risk, and extensive installation of alcohol dispensers for glove-on hand rubbing. This integrated infection control approach was implemented at a SARS designated hospital (‘study hospital’) where NPIRs were not available. The number of HCWs who contracted SARS in the study hospital was compared with the number of HCWs who contracted SARS in 86 Taiwan hospitals that did not use the integrated infection control strategy. Two HCWs contracted SARS in the study hospital (0.03 cases/bed) compared with 93 HCWs in the other hospitals (0.13 cases/bed) during the same three-week period. Our strategy appeared to be effective in reducing the incidence of HCWs contracting SARS. The advantages included rapid implementation without NPIRs, flexibility to transfer patients, and re-inforcement for HCWs to comply with infection control procedures, especially handwashing. The efficacy and low cost are major advantages, especially in countries with large populations at risk and fewer economic resources.

Alpha Testing of a System for Creating On-Demand Positive and Negative-Pressure Isolation Environments in Typical Emergency Department Rooms

Study Objectives: With heightened concerns over nuclear, biological or chemical attacks or accidents, the federal government has mandated increases in the number of positive and negative pressure isolation rooms. Currently these rooms represent a scarce hospital resource, especially in emergency departments (EDs). We undertook Alpha testing of a portable environmental control system to evaluate its ability to produce stable positive or negative pressure environments in typical ED patient care rooms.

Quantification of AirborneMycobacterium tuberculosisin Health Care Setting Using Real-Time qPCR Coupled to an Air-Sampling Filter Method

Abstract Mycobacterium tuberculosis infection remains one of the major public health issues worldwide. Current qualitative assays (only positive or negative results) do not provide comprehensive information regarding health risk of M. tuberculosis. This study attempted to develop a quantitative assay to measure air concentration of M. tuberculosis in a health care setting. A total of 22 air samples were taken from the negative pressure isolation rooms of tuberculosis patients. The air was filtered through a Nuclepore filter with sampling time of 8 h. The DNA of M. tuberculosisin these airborne samples was then analyzed by the ABI 7700 real-time quantitative polymerase chain reaction (real-time qPCR) system. The real-time qPCR method could perform measurements of counts in a dynamic range of over 6 orders with a high sensitivity. The measured M. tuberculosis concentrations varied widely, from 1.43 × 10 copies/m3 to 2.06 × 105 copies/m3. Comparisons among airborne M. tuberculosis levels, sputum smear, resul...

Rapid Creation of a Temporary Isolation Ward for Patients With Severe Acute Respiratory Syndrome in Taiwan

To rapidly establish a temporary isolation ward to handle an unexpected sudden outbreak of severe acute respiratory syndrome (SARS) and to evaluate the implementation of exposure control measures by healthcare workers (HCWs) for SARS patients. Rapid creation of 60 relatively negative pressure isolation rooms for 196 suspected SARS patients transferred from 19 hospitals and daily temperature recordings of 180 volunteer HCWs from 6 medical centers. A military hospital. Of the 196 patients, 34 (17.3%) met the World Health Organization criteria for probable SARS with positive results of serologic testing for SARS-associated coronavirus (SARS-CoV), reverse transcriptase polymerase chain reaction (RT-PCR) from nasopharyngeal or throat swabs for SARS-CoV, or both. Seventy-four patients had suspected SARS based on unprotected exposure to SARS patients; three of them had positive results on RT-PCR but negative serologic results. The remaining 88 patients did not meet the criteria for a probable or suspected SARS diagnosis. Of the 34 patients with probable SARS, 13 were transferred to medical centers to receive mechanical ventilation due to rapid deterioration of chest x-ray results, and three patients died of SARS despite intensive therapy in medical centers. During the study period, one nurse developed probable SARS due to violation of infection control measures, but there was no evidence of cross-transmission to other HCWs. Despite the use of full personal protection equipment, the facility failed to totally prevent exposures of HCWs to SARS but minimized the risk of nosocomial transmission. Better training and improvements in infection control infrastructure may limit the impact of SARS.

Infection control practices for SARS in Lao People's Democratic Republic, Taiwan, and Thailand: Experience from mobile SARS containment teams, 2003

BackgroundDespite available recommendations on infection control for severe acute respiratory syndrome (SARS), information is limited on actual practices in Asian hospitals during the epidemic. We describe practices observed by mobile SARS containment teams (mobile teams) during outbreak investigations.MethodsWe retrospectively summarized infection control practices observed in hospitals visited by mobile teams in the Lao People's Democratic Republic (PDR), Taiwan, and Thailand, during March and April 2003.ResultsMobile teams investigated 22 reports of SARS in 20 hospitals (1, 5, and 14 hospitals in Lao PDR, Taiwan, and Thailand, respectively). Facilities ranged from urban hospitals with negative-pressure isolation rooms and high-efficiency particulate air filtration to rural hospitals with patient rooms open to outside air circulation and intermittent running water. At the time of mobile team visits, 5 (25%) hospitals implemented infection control practices consistent with World Health Organization recommendations on visitor policies, private negative-pressure rooms, and personal protective equipment.ConclusionsEarly in the SARS epidemic, mobile teams found wide variations in infection control practices and resources among Asian hospitals evaluating patients for SARS, indicating the importance of ongoing assessment during SARS preparedness. Mobile teams are one mechanism to assess practices and promote implementation of recommended infection control measures.

Hospital disaster preparedness in Los Angeles County, California

Study objectives: We characterize disaster preparedness among a cohort of hospitals, focusing on practice variation, plan characteristics, and surge capacity.Methods: This was a descriptive, cross-sectional study using an in-person hospital survey and a 117-item questionnaire in Los Angeles County, CA. The study included 45 of the 81 designated 911 receiving hospitals, including private and tertiary care facilities. Observations include a description of hospital disaster plans, modes of intra- and interhospital communication, community and interagency involvement, decontamination capability and training, drills, pharmaceutical stockpiles, and each facility's surge capacity (assessed by monthly emergency department [ED] diversion status, number of available beds, ventilators, and negative pressure isolation rooms). Additional measures of preparedness included whether hospitals had the following: mutual aid agreements with other hospitals, long-term care facilities, and medical vendors; protocols for canceling elective surgeries and early in-patient discharge; surveillance systems; ongoing training with local emergency medical services and fire departments; communication with the public health department; volunteer credentialing systems; and a protocol for mass fatality incidents.Results: Ninety-five percent had adopted the Hospital Emergency Incident Command System, and 100% used the ReddiNet, a radio-based communications network. Ninety-five percent had memoranda of understanding with medical suppliers. However, 67% never had joint training programs with local police and fire agencies, and only 16% and 7% had written mutual aid agreements with other hospitals and long-term care facilities, respectively. Eighty-eight percent of hospitals had level B and/or C personal protective equipment, and 44% had decontamination facilities suitable in inclement weather. Ninety-six percent of respondents noted a nurse shortage, 58% had a monthly ED diversion rate of greater than 20%, and 69% estimated a surge capacity of less than 20 beds. Fifty-eight percent of responding hospitals had fewer than 10 negative pressure isolation rooms, only 36% had more than 10 ventilators, and 55% did not keep a stockpile of antibiotics or antidotes. Although 93% and 98%, respectively, had protocols for canceling elective surgeries and early in-patient discharge, only 64% had plans in place for a mass fatality incident.Conclusion: There are no objective measures of “hospital preparedness” or “hospital surge capacity.” In addition to establishing such standards, focus must be placed on enhancing interagency and interhospital communications. Current numbers of available hospital beds, ventilators, isolation rooms, and pharmaceuticals may be insufficient to effectively care for victims of large-scale disasters and other public health emergencies.

Clinical and Laboratory Features of Severe Acute Respiratory Syndrome Vis-À-Vis Onset of Fever

Study objectives:Severe acute respiratory syndrome (SARS) is a rapidly progressive disease caused by a novel coronavirus (CoV) infection. However, the disease presentation is nonspecific. The aim of this study was to define clearly the presentation, clinical progression, and laboratory data in a group of patients who had SARS.Design:Retrospective observational study.Setting:A tertiary care medical center with 51 negative-pressure isolation rooms in Taipei, Taiwan.Patients:Fifty-three patients with SARS seen between April 27 and June 16, 2003.Results:Fever (ie, temperature > 38°C) was the most common symptom (98%) and the earliest. When admitted to the isolation unit of the hospital for observation, most patients reported nonspecific symptoms associated with their fever. Only two patients with preexisting illnesses had cough on the same day the fever began. Eventually, 39 patients (74%) developed cough, beginning at a mean (± SD) time of 4.5 ± 1.9 days after fever onset, and 35 patients (66%) had diarrhea beginning at a mean time of 6.0 ± 3.3 days after fever onset. Thirty-one patients (59%) had abnormal findings on chest radiographs on hospital admission, and all but 1 patient (98%) eventually developed lung infiltrates that were consistent with pneumonia. The majority of patients (63%) first developed unifocal infiltrates at a mean time of 4.5 ± 2.1 days after fever onset, while in 37% of patients the initial infiltrates were multifocal, appearing at a mean time of 5.8 ± 1.3 days after fever onset. Common laboratory findings included lymphopenia (on hospital admission, 70%; during hospitalization, 95%), thrombocytopenia (on hospital admission, 28%; during hospitalization, 40%), elevated lactate dehydrogenase (on hospital admission, 58%; during hospitalization, 88%), creatine kinase (on hospital admission, 18%; during hospitalization, 32%), and aspartate aminotransferase or alanine aminotransferase levels (on hospital admission, 27%; during hospitalization, 62%). Throat or nasopharyngeal swab for SARS-CoV by reverse transcriptase polymerase chain reaction (PCR) and real-time PCR was positive in 40 of the 47 patients (85%) in whom the test was performed.Conclusions:None of the presenting symptoms or laboratory findings are pathognomonic for SARS. Even though cough developed in a majority of patients, it did not occur until later in the disease course, suggesting that a cough preceding or concurrent with the onset of fever is less likely to indicate SARS. While PCR for SARS-CoV appears to be the best early diagnostic test currently available, it is clear that better methods are needed to differentiate between SARS and non-SARS illness on initial presentation.

The Use of Video in Infection Control

BACKGROUND: Our institution, a 1200-bed teaching hospital in New York City, mobilized in response to the threat of SARS in 2003. PROJECT: The New York-Presbyterian Hospital SARS Task Force decided to develop a videotape that depicts the step-by-step technique for donning and removing the personal protective equipment worn during the care of SARS patients. This videotape was written and performed by hospital staff members, and produced in conjunction with Columbia University, Center for Biomedical Communications. RESULTS: A video format was chosen as the best way to demonstrate visual techniques that are difficult to show via written materials. We wrote a script, built a set to replicate a negative-pressure isolation room, and had staff members from the Department of Epidemiology take prominent roles. The videotape opens with a brief introduction to the global SARS situation in 2002-2003 utilizing a voice-over and graphics. The action then transitions to the set where a narrator provides the necessary explanations. The viewers see the role of the “Observer,” a nurse whose task it is to enforce the SARS policies, and watch a social worker, housekeeper, and physician step through the techniques of donning and removing personal protective gear. LESSONS LEARNED: Through this collaborative effort, our facility has a highly effective tool that educates our staff in the steps required to themselves and their colleagues from a life-threatening illness.

Polymerase chain reaction used for the detection of airborne Mycobacterium tuberculosis in health care settings

Background Tuberculosis (TB) has re-emerged as a major infectious disease in several areas in the world. Airborne tubercle bacilli produced by individuals with pulmonary TB and droplet nuclei remain suspended in the air for a long time. This study attempts to use a sensitive polymerase chain reaction (PCR) analytic method coupled with a filter sampling method to detect the presence of airborne Mycobacterium tuberculosis (MTb) in health care settings. Methods Patients with TB history were recruited from a medical intensive care department and negative-pressure isolation rooms at Chang Gung Memorial Hospital in Taichung City, Taiwan, Republic of China. The exhaled gas from different patients with TB who were mechanically ventilated in the intensive care department was collected using a polycarbonate (PC) membrane or polytetrafluoroethylene (PTFE) filter. Airborne MTb concentrations in air exhausted through a bacterial filter attached to a mechanic ventilator were studied. Indoor air samples were taken through a 3-piece cassette with a filter (PC/PTFE) in patient rooms. MTb concentrations in these filters were analyzed using the PCR method. Results Overall, 75% (12/16) of the exhaled-gas samples in PTFE filters and 25% (4/16) of samples in PC filters were detected as having positive MTb-specific DNA products. Exhausted air from the bacterial filters in mechanic ventilators was found to have positive PCR results (57% in PC filters and 14% in PTFE filters) for MTb. Both negative-pressure isolation rooms and outpatient department areas in the TB center had positive samples (40%-60% in PC/PTFE filters) containing MTb by PCR amplification. Conclusions Health care settings were sufficient for various risk factors, including physical, chemical, and biologic hazards. Infectious agents are produced by aerosolization that results in human respiratory-related diseases. The indoor air quality of the entire hospital environment should, therefore, be monitored by health care personnel and the public.

Responding to the severe acute respiratory syndrome (SARS) outbreak: Lessons learned in a Toronto emergency department

Responding to the severe acute respiratory syndrome (SARS) outbreak: Lessons learned in a Toronto emergency department

A determination of healthcare worker exposure to Mycobacterium tuberculosis in two Californian hospitals

The US Centers for Disease Control and Prevention (CDC) recommends the prompt and sustained placement of potentially infectious tuberculosis patients in to negative-pressure isolation rooms, to help prevent other patients and workers, who remain outside of the room, from exposure to potential aerosols of Mycobacterium tuberculosis. The purpose of this study was to assess the potential for healthcare worker exposure to such aerosols and, to study compliance with the CDC guidelines. All room locations of culture-positive pulmonary TB patients were identified retrospectively for a one-year period at two hospitals. Placement in a negative-pressure isolation room was delayed for >24h after admission in 30% of 54 patients at hospital 1, and for 56% of nine patients at hospital 2. The median delay in isolation was three days at hospital 1, and five days at hospital 2. At hospital 1, of the 16 patients with delayed or no isolation, 14 (88%) were AFB smear-positive, and 12 (75%) were admitted to the hospital during the winter months. At hospital 2, of five patients with delayed or no isolation, two (40%) were AFB smear-positive, and four (80%) were admitted to the hospital during the winter months. The main reason for non-isolation was failure to initiate and sustain isolation for all suspect tuberculosis patients during the winter. These delays may reflect an insufficient number of isolation rooms to accommodate an increased usage of isolation rooms during the winter months. Delays in suspecting tuberculosis also contributed to non isolation. For 33% of the non-isolated patients, recognition of the diagnosis was delayed for three or more days. Patients were hospitalized on most adult inpatient wards, and virtually every hospital location that had these patients also had, non-isolated sources of mycobacterial aerosol. All workers were at risk of exposure, although the risk varied by hospital location, and should be tuberculosis skin-tested, at least annually. Suspect and known tuberculosis patients should be isolated until they are demonstrated to be non-infectious.

Assessing the risk of tuberculosis infection among healthcare workers: the Melbourne Mantoux Study. Melbourne Mantoux Study Group.

To determine the potential prevalence of nosocomial infection with Mycobacterium tuberculosis among hospital employees in teaching hospitals in Melbourne. Cross-sectional survey of positive tuberculin skin test (Mantoux) responses among employees in 14 public hospitals in Melbourne, January 1996 to April 1999. All consenting employees in participating hospitals (4,070 healthcare and 4,298 non-healthcare workers; participation rates, 13%-66%). Prevalence of positive responses to tuberculin skin tests among healthcare and non-healthcare workers and association with employee and hospital characteristics. Healthcare workers were significantly more likely to have a positive tuberculin response than non-healthcare workers (19.3% versus 13.7%; odds ratio, 1.5; 95% CI, 1.3-1.7; P<0.001). Multivariable analysis revealed that age, country of birth (high versus low tuberculosis [TB] prevalence), history of BCG (bacille Calmette-Guérin) vaccination, years since last BCG, occupation (healthcare versus non-healthcare worker) and years of hospital employment were all significantly associated with a positive response. Rates of positive responses among employees varied greatly between hospitals (6%-35%). These differences were not explained by employee characteristics, hospital TB patient load (number of admissions or bed-days) or percentage of hospital patients from countries with high TB prevalence. The hospital with the highest rate of positive responses was notable for its lack of negative-pressure isolation rooms for TB patients. Positive tuberculin responses are relatively common among hospital employees in Melbourne, with rates varying between hospitals and being higher among healthcare than non-healthcare workers. Employee characteristics, such as age, country of birth and past BCG status, explain little of this variation. More emphasis on TB infection control measures and regular staff screening may be needed.

Air Volume Migration from Negative Pressure Isolation Rooms during Entry/Exit

Abstract Negative-pressure isolation rooms (NPIRs) are used to isolate patients who have a suspected or known airborne infectious disease from the general hospital environment. When a person passes through an NPIR doorway, there exists an exchange of air between the isolation room and the area beyond its door. In a recent study, National Institute for Occupational Safety and Health researchers used sulfur hexafluoride tracer gas to examine the magnitude of air volume migration (AVM) as a function of several independent variables. A small cart carried a mannequin through a doorway separating a laboratory NPIR and a sulfur hexafluoride measurement chamber. The configuration provided simulated entry/exit of a healthcare worker through the doorway. Upon completion of experiments using a swinging door (including various cycle speeds for the door), a sliding door was installed and the experiments were repeated. In all cases examined, air flow rate differential between the air supplied to, and exhausted from, the NPIR was the only statistically significant factor in determining the level of AVM. Across the range of flow differentials examined (50 to 220 ft3/min), AVM ranged from 35 to 65 ft3. This range of AVM remained statistically unchanged regardless of door type, operating speed of the door, or entry to or exit from the NPIR. (Although entry/exit did significantly increase AVM, travel direction, whether entering or exiting the NPIR, did not.) By knowing the level of AVM during entry/exit through a doorway—a cause of airborne contaminant migration through a facility—a more complete assessment of the risk of transmission of an airborne infectious disease is made possible. This study shows that an anteroom or buffer zone outside the contaminated area's doorway will offer a degree of containment during entry/exit not otherwise obtainable. While this study concerned itself primarily with the engineering control of the transmission of airborne infectious diseases provided by ventilation systems, the results are applicable to any environment where a clean area is separated from a less clean area by a doorway. Hayden, II, C.S.; Johnston, O.E.; Hughes, R.T.; Jensen, P.A.: Air Volume Migration from Negative Pressure Isolation Rooms During Entry/Exit.