Development of an Empirical Model to Aid in Designing Airborne Infection Isolation Rooms

Abstract

Airborne infection isolation rooms (AIIRs) house patients with tuberculosis, severe acute respiratory syndrome (SARS), and many other airborne infectious diseases. Currently, facility engineers and designers of heating, ventilation, and air-conditioning (HVAC) systems have few analytical tools to estimate a room's leakage area and establish an appropriate flow differential (DeltaQ) in hospitals, shelters, and other facilities where communicable diseases are present. An accurate estimate of leakage area and selection of DeltaQ is essential for ensuring that there is negative pressure (i.e., pressure differential [DeltaP]) between an AIIR and adjoining areas. National Institute for Occupational Safety and Health (NIOSH) researchers evaluated the relationship between DeltaQ and DeltaP in 67 AIIRs across the United States and in simulated AIIR. Data gathered in the simulated AIIR was used to develop an empirical model describing the relationship between DeltaQ, DeltaP, and leakage area. Data collected in health care facilities showed that the model accurately predicted the leakage area 44 of 48 times. Statistical analysis of the model and experimental validation showed that the model effectively estimated the actual leakage area from -39% to +22% with 90% confidence. The NIOSH model is an effective, cost-cutting tool that can be used by HVAC engineers and designers to estimate leakage area and select an appropriate DeltaQ in AIIRs to reduce the airborne transmission of disease.

Evaluation of potential employee exposures to Mycobacterium tuberculosis at an elephant refuge.

“…This was likely from employee traffic during the September 12, 2012, test. This result is consistent with other studies that have shown anteroom contamination resulting from employee movement [Hayden et al 2007;Johnson et al 2009;Hyttinen et al 2011]. As a note, the Centers for Disease Control and Prevention (CDC) defines an anteroom as "a small room leading from a corridor into an airborne infection isolation room.…”

Different Types of Door-Opening Motions as Contributing Factors to Containment Failures in Hospital Isolation Rooms

“…Although there have been many studies evaluating the performance of such rooms with regard to the maintenance of the pressure differential across the doors when closed [15][16][17][18], there have been relatively fewer studies assessing how dooropening motions and healthcare worker passage through the door can affect the performance of such rooms [19][20][21][22]. Yet, at least one analytical case report has demonstrated that containment failure may result from simply opening isolation room doors [23].…”

Airborne Infection Isolation Rooms – A Review of Experimental Studies

“…Door-slot and other types of leakage are important for the performance of AIIRs. Hayden et al [43] studied leakage area, flow differential, and pressure difference in an experimental room where leakage areas were known. He developed the following model (in SI units) between leakage area ( A ), pressure difference (Δ p ) and the flow differential (Δ Q = exhaust flow rate − supply flow rate): A = 4.891·Δ Q 1.170 /Δ p 0.602 .…”