Page 111 - School Infection Control Handbook - 2010

Chapter 6: Equipment for Infection Control
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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.
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.
Air cleaning through air
filtration in general
mechanical ventilation
systems
The level of filtration can be
increased to filter out microbes,
which are microscopic.
The equipment must be
designed to handle a higher-
rated filter based on its fan
power.
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