School Infection Control Handbook - 2010

Chapter 6: Equipment for Infection Control

Chapter 6.D. Using Ventilation to Help Reduce Disease Transmission

Introduction Contracting an infectious disease is related in part to the amount of microbes a person is exposed to. Thus, if the volume of microbes in the air is reduced, so is the risk of contracting the disease. Airborne diseases can be reduced by ventilation and related technologies. Because microbes are particulate matter, this section discuss the use of two ventilation technologies appropriate for use in school buildings to remove “bioaerosols,” which are biological particles suspended in the air. Air-cleaning technology is not discussed because it removes only vapors and gases (not particulates) from the air. Ventilation Technology How It Works Comments

Dilution and removal of contaminated air using a general mechanical ventilation system

One of the system’s roles is to exhaust a certain percentage of air from the building and to replenish that amount with fresh air. The amount of air exchange per hour can be increased for infection-control purposes. The level of filtration can be increased to filter out microbes, which are microscopic.

This option enables the existing system (while it is operating) to be used as is, with air exchanges per hour increased as needed. Thus, only operating costs, not capital costs, are incurred. The equipment must be designed to handle a higher- rated filter based on its fan power.

Air cleaning through air filtration in general mechanical ventilation systems

Research Findings A multidisciplinary expert panel reviewed 40 studies conducted between 1960 and 2005 and concluded that higher ventilation rates reduced the transmission and spread of infectious agents in buildings. 1 In their report, the authors recommended that schools and similar high-density facilities increase their ventilation rates during peak influenza season. Although the authors found that there was strong and sufficient evidence to demonstrate the association between ventilation, air movement in buildings, and the transmission/spread of infectious diseases such as measles, tuberculosis, chickenpox, influenza, smallpox, and severe acute respiratory syndrome, they found that there was not enough research to specify the ventilation requirements in schools. 1 In addition, a controlled study in office buildings found a link between short-term sick leave, often associated with respiratory illness, and low ventilation rates. Occupants of buildings with low ventilation rates and high occupant densities experienced far higher rates of respiratory illness than did occupants of similar buildings with higher ventilation rates. 2

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