Indoor Air Resources

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Air Sick? IAQ & Infection Control

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By: Robert Martin, CAFS, Associate Category Manager, Kimberly-Clark Professional Filtration  |   10.09.14

Indoor air pollutants are unwelcome visitors in healthcare facilities, and poor indoor air quality (IAQ) may cause outbreaks of Sick Hospital Syndrome (SHS), causing headaches, eye and skin irritation and other symptoms. It may also place patients at risk for developing a healthcare-acquired infection (HAI). 

The pressure to maintain superior IAQ is acute in healthcare facilities because of the large numbers of people at risk for developing an HAI, including post-operative patients, immuno-compromised patients, seniors and infants. 

The scope and costs of HAIs in the U.S. are staggering:

  • The CDC estimates that one out of twenty-five hospital patients will contract an HAI.
  • Overall annual direct medical costs to hospitals of HAIs range from $28-45 billion.

Sources of IAQ Problems

Infectious agents linked to airborne transmission in healthcare facilities include Aspergillus, Mycobacterium tuberculosis, Bacillus spp, VZV, measles virus (i.e., rubeola), Legionella bacteria, methicillin-resistant Staphylococcus aureus, and smallpox virus (i.e., variola major). 

Decreased performance of healthcare facility HVAC systems, filter inefficiencies, improper installation, and poor maintenance practices – including removal of used filters – can contribute to the spread of airborne HAIs. For example, contaminated air ventilation systems, gaps in and around filter banks and heavy soil and debris upstream of poorly maintained filters have been implicated in healthcare-associated outbreaks of aspergillosis. 

Construction and renovation of healthcare facilities can also cause IAQ problems. Environmental disturbances (of soil, water, dust and decaying organic matter) associated with construction activities near healthcare facilities can release microorganisms into the air, posing airborne disease threat risks for at-risk patients. The increasing age of hospitals and other healthcare facilities is also generating ongoing need for repair and remediation work (e.g., installing wiring for new information systems, removing old sinks, and repairing elevator shafts) that can introduce or increase contamination of the air in patient-care environments. 

Solving IAQ Problems

Microorganisms, dust, allergens and other respiratory illness triggers that occur within a building can be eliminated or significantly reduced by a building’s HVAC system. The key HVAC system component for reducing these triggers is effective air filtration, which provides a prime defense against indoor air pollutants. 

When evaluating filters, check their Minimum Efficiency Reporting Value (MERV) as demonstrated by the ASHRAE 52.2 Test Standard. A MERV 1 is considered least efficient, while a MERV 16 is most efficient. (Note that HEPA and ULPA filters are not tested according to ASHRAE 52.2 and therefore do not have MERVs.) In most healthcare facilities (not including operating rooms, labs, isolation wards or intensive care units), the best filter choice – per ASHRAE and the American Institute of Architects – is a MERV 14-16 filter with a MERV 8 pre-filter. 

Look beyond the filter’s MERV as well to the Fractional Particle Size vs. Particle Diameter Curve that is included with the ASHRAE 52.2 test report. The curve will provide the efficiency of the filter over three particle size ranges: E1 (very fine particles in the 0.3 to 1.0 micrometer range), E2 (fine particles in the 1.0 to 3.0 micrometer range), and E3 (coarse particles in the 3.0 to 10.0 micrometer range). 

Submicron particle capture is critical: Lung-damaging dust can be as small as 0.5 micrometers, while some bacteria can be as small as 0.3 micrometers. That means high E1 and E2 efficiencies are critical for good IAQ. 

Balanced Efficiency

Consider filters that have filter media with a good balance of mechanical particle capture efficiency and electret particle capture efficiency (via an electrostatic charge). The electrostatic effects are particularly useful in increasing the capture efficiency for submicron particles. In addition, filters with electret-charged media almost always deliver lower airflow resistance in the same filter construction as mechanical-only filters, which translates into reduced energy costs. 

Selecting the proper air filter – one with electret-charged filter media – can help you achieve your IAQ and infection control goals while reducing operating costs.

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