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In the new normal after COVID-19, infection preventionists will need to become more knowledgeable about and involved in the functionality of air ventilation in health care settings.
The importance of ventilation in health care and non–health care settings has become evident amid the COVID-19 pandemic. Decreased performance of health care facility heating, ventilation, and air conditioning (HVAC) systems, including filter inefficiencies, improper installation, and poor maintenance, can contribute to the spread of health care-associated infections (HAIs), according to various research findings. Infection preventionists (IPs) who have a basic understanding of ventilation systems and associated risks might feel more confident and comfortable collaborating with architects, facility designers, and engineers. COVID-19 is 1 of many diseases transmitted from a respiratory source.
How does air play a role in disease transmission? The aerosolized transmission of disease happens through droplet and airborne means.1 Droplet transmission of disease can occur when
bacteria or viruses travel on relatively large respiratory particles that people sneeze, cough, or exhale through talking, singing, or shouting. These droplets travel short distances (usually less than 6 ft) before settling and can be loaded with infectious particles. Infectious particles that contact a person’s eyes, nose, or mouth can cause infection. If they fall on surfaces, they can be transferred onto the hand of someone who unknowingly rubs their eyes, nose, or mouth, causing possible self-contamination.
Airborne transmission is defined as infections transmitted through exposure to infectious, pathogen-containing, small droplets and particles suspended in the air over long distances that can persist in the air for long times.2 The main differences between these 2 transmission types come down to particle size and distance traveled: Droplets are thought to be larger and don’t travel as far; aerosols are smaller and can travel quite a distance. The Centers for Disease Control and Prevention (CDC) recommended isolation precautions for diseases like measles or chicken pox, which are airborne, and mumps, which is transmitted by droplet.3 IPs understand the importance of these precautions but may know less about how these measures work to protect patients and staff.
“The importance of good air quality in controlling and preventing airborne infections in health care facilities cannot be overemphasized,” wrote Anjali Joseph, PhD, the director of research at the Center for Health Design, a company that plans health care facilities, in a 2006 study. “Providing clean filtered air and effectively controlling indoor air pollution through ventilation are 2 key aspects of maintaining good air quality.”4
Knowing how important air quality and ventilation are, IPs might better converse with health care architects, designers, and facilities groups if they understand the basics of clean, filtered air and ventilation. Basic terms include the following:
• Self-closing doors are mandatory for both of these areas to help maintain the correct pressure differential.
• Variable pressure rooms (rooms where the ventilation can be manually switched between positive and negative pressure) are no longer permitted in new construction or renovation, and their use in existing facilities has been discouraged because of difficulties in assuring the proper pressure differential, especially for the negative pressure setting, and the potential for error associated with switching the pressure differentials for the room. Continued use of existing variable pressure rooms depends on collaboration between engineering and infection control. Both positive- and negative-pressure rooms should be maintained according to specific engineering specifications.13
• ASHRAE Standard 170, Ventilation of Health Care Facilities, requires each isolation room to have a permanently installed visual device or mechanism to constantly monitor the air pressure differential of the room when occupied by a patient who requires isolation. The CDC states that airflow direction should be maintained and verified, preferably daily, even when the room is unoccupied, using either a visual means of indication (eg, smoke tubes and flutter strips) or manometers.14
5. Temperature is defined as the degree of hotness or coldness measured on a definite scale.
• In health care, normal operating temperature set points should be maintained based on the existing licensing requirements for the space use and occupancy. Consult FGI for specific guidance.
• ASHRAE Standard 170 requires temperatures ranging from 68 °F to 75 °F for most patient care areas. Cool temperature standards (68 °F–73 °F [20 °C–23 °C]) are usually related to operating rooms, clean workrooms, and endoscopy suites.
• Temperatures above about 75 °F (24 °C) appear to universally lower airborne bacterial survival.15
• Virus survival, in general, decreases as temperatures rise. However, many factors, such as humidity, presence of organic matter, and whether they are DNA or RNA viruses, influence survivability. Much more research regarding temperature and its effect on viruses is ongoing.
As the above tutorial indicates, the current information on air in health care and public buildings can be overwhelming. The really heavy engineering and design details of ventilation are best left to the architects, engineers, and the facilities groups. But knowing the basics of air quality and air handling, as well as their relationship to possible disease transmission, could benefit IPs.
SHARON WARD-FORE, MS, MT(ASCP), CIC, FAPIC, is an infection prevention consultant in Chicago, Illinois. She is the Infection prevention adviser for Metrex Infection Prevention/Envista Holdings, an APIC Text clinical editor, and a contributing Editorial Advisory Board member of Infection Control Today®.