In hospitals, it is critical maintaining IAQ. Excess moisture in wall spaces can foster mold growth. Above, a Fluke 971 Temperature Humidity Meter collects humidity and temperature measurements.

IAQ is a significant issue in health care. Airborne organisms common in the environment can pose a serious threat to a patient who is immune-compromised. A patient ill with a respiratory infection can spread dangerous microbes to other patients, staff, and visitors. Yet, it’s easy to understand the steps required to establish, monitor, and maintain safe, comfortable air quality and prevent airborne nosocomial (hospital-acquired) infections.

To deliver IAQ appropriate for an environment of care, facility managers, contractors, and maintenance personnel should take action in four areas:

1.Set up administrative controls. These are policies and procedures to identify and manage risk.

2.Understand facility function and design requirements. For instance, hospitals must provide contaminant control facilities to protect immune-compromised patients and isolate those with infections that can be spread through the air, such as tuberculosis.

3.Monitor and document air quality and system performance to guide system operation and maintenance.

4.Develop contingency plans to guide responses when construction and renovation projects arise or emergencies occur, such as leaks, spills, and floods.

The Joint Commission on the Accreditation of Healthcare Organizations (JCAHO) has outlined some basic environment of care standards:

• Hospitals must assess and control risks, including those related to HVAC and other utility systems.

• They must regularly inspect, test, and maintain those systems.

• They must design, install, and maintain ventilation equipment to serve airborne contaminant control facilities, and document their maintenance activities.

In addition, hospitals are expected to carefully assess the risks construction activity raises for air quality and infection control. Bottom line: There is plenty to consider in order to maintain appropriate IAQ in a health care surrounding.


Some medical procedures and patient conditions increase risk of exposure to airborne microorganisms. Air quality management is vital in reducing these risks.

The Centers for Disease Control (CDC) provides detailed hospital rooms guidelines for managing the risk of airborne infection:

Operating rooms:In operating rooms, patient tissues and organs are exposed to the air, creating opportunity for airborne microbes to enter the surgical site. In addition, use of cautery and lasers can release materials and organisms into the atmosphere. An effective operating room ventilation system introduces HEPA-filtered air through laminar flow from the ceiling and removes exhaust air through returns at the margins of the room. Positive pressure in the room keeps air moving from clean (within the room) to dirty. Use of negative-pressure anterooms and attention to keeping doors closed helps maintain correct pressure relationships.

Protective environment rooms:Immune-compromised patients, such as organ transplant patients receiving immunosuppressive treatment, may be unable to resist infection by common organisms such as Aspergillus Fumigatus, a common soil fungus that is able to live and reproduce in the warmth and moisture of the human lung. Aspergillosis is difficult to diagnose and treat, and is fatal more than 80 percent of the time. In rooms housing such patients, supply HEPA-filtered air at a rate of six to 10 air changes an hour to maintain positive pressure (pressure differential greater than 0.01 inches water gauge [2.5 Pa]) and keep air flowing from the room out.

Patient isolation rooms:Negative-pressure isolation rooms house patients with infectious diseases spread by air (M. tuberculosis is one example). Air exhaust volume exceeds air intake by about 10 percent, or more than 125 cubic feet per minute, so that air flows from corridor or anteroom into the patient space. Carefully seal ducts, doors, walls, and windows to maintain negative pressure and help control airflow direction. You can take further steps - such as placing local exhaust ventilation near the patient’s head, supplying surgical masks for the patient, and placing ultraviolet light fixtures in the room - to reduce the concentration of airborne bacteria.

Using a Fluke 922, a technician in a hospital tests the pressure differentials between aII spaces (or construction zones) and adjacent uncontrolled areas to verify that pressures meet specifications and air is flowing as required, from clean to dirty. Contractors can also test to verify that temporary enclosures, barriers, and negative-air machines are correctly installed and functioning in a hospital environment.


Even in a well-designed facility, performance can decline over time. Blowers fail. Filters do their jobs but eventually become clogged, reducing airflow. A door left open or a window improperly sealed can disrupt pressure and airflow. A planned program of performance monitoring and maintenance can give you the base of information you need to detect and remedy such problems before they compromise air quality and health.

Health and comfort depend on a number of air quality factors, including the following:

Temperature- Primarily a comfort factor, though temperature extremes could affect health.

Relative humidity- In combination with temperature, humidity is an important comfort factor.

Pressure relationships- These govern the direction and speed of airflow.

Airborne particle sizes and numbers- They can indicate effectiveness of filtration and suggest the need for further analysis to determine particle content.

The nature of airborne particles- Some particles are inert and harmless. Others can trigger allergies, and some microorganisms, such as airborne viruses and bacteria and even common fungus spores, such as A. Fumigatus, can cause infection.

Surface temperatures- Surfaces below the dew point can cause condensation. Damp surfaces in turn help create conditions for mold growth.


Key to your ability to control these air quality parameters is measurement. A consistent program to monitor and measure indoor air conditions serves to verify that targeted air quality conditions are being met; provide early warning when conditions change, so corrections can be made; and create evidence of sound management oversight. (Your track record could prove useful in the event of a question or litigation.)

You must base an effective air quality program on measurable air quality standards. Establish air quality target levels and pressure requirements appropriate for the function of the space in question. Air quality acceptable in a cafeteria, for instance, would not meet standards for a patient isolation room. Most restrooms don’t need a HEPA-filtered air supply, but they should have negative pressure.

Next, set a schedule for monitoring and measuring air quality and air-handling performance. People change things. For instance, they open and close doors, windows, and air vents. Blower motors and drives fail. Technicians may install filters incorrectly, or fail to replace them on schedule.

Measurement of the following items using the appropriate instruments/processes will help you identify emerging issues:

Pressure and flow- Air pressure sensors installed in patient isolation facilities show from the outside whether the room is meeting pressure requirements. A hand-held pressure test probe inserted under the door provides a check. A smoke tube provides a visible indication of airflow.

Temperature and humidity- A hand-held tester provides a quick reading of relative humidity/temperature parameters.

Particles: Number and nature- A hand-held particle counter shows numbers and sizes of airborne particles. Use the counter to check filter performance (air downstream from a 90 percent filter should be much cleaner than the air upstream, while air downstream from a HEPA filter should be virtually particle-free). Access ports installed in air ducts make it easy to test particle levels upstream and downstream of filters.

Many factors can cause an increase in particle numbers. Is the entrance open to a dusty construction zone? Have hospital staffers rushed to a room to deal with an emergency situation? (Humans shed one-half million particles each minute.) Or has a plumbing leak enabled a colony of mold to grow? Particle counters determine the number but not the nature of airborne particles. Verifying the nature of particles requires the capture of samples on a test medium, which is then cultured and analyzed to determine the species and concentration of fungi (the most likely health threat) present. This process can require several days.

Tracking airborne gases- CO2 is a natural byproduct of human respiration, so it can be used as an indicator of IAQ. If CO2 levels are excessive, you can assume that other gases - such as volatile organic compounds (VOCs) emitted by building materials, paints, and carpets - are also building up. CO2 levels beyond 1,000 ppm may show that not enough fresh outside air is being mixed into the indoor air supply to dilute gases. You can measure CO2 levels with a hand-held meter.

Carbon monoxide is a poison. You can use both fixed and hand-held CO testers to detect the presence of this dangerous gas.

Measuring filter performance- Air filter efficiency actually increases during use as trapped particles increase the density of the filter medium. Over time, however, the accumulation of particles impedes airflow. Install monitoring devices, such as manometers, or gauges to measure the pressure drop across the filter. When the pressure drop exceeds the filter manufacturer’s specifications, replace the filter.

Moisture and mold- Moisture meters measure moisture levels on and within materials, such as wallboard, concrete, and wood. These materials can absorb significant amounts of water and, when the moisture remains and temperature is right, provide a base for the growth of mold, which releases spores into the air.

Construction can generate large amounts of dust and debris, made worse by movement of workers and equipment in and out of containment zones. Taking regular particulate measurements with a laser particle counter is considered the best way to identify and troubleshoot these problems. (In use above is a Fluke 983.)


If not managed correctly, construction can trigger changes that damage air quality and threaten patient welfare. Hospital accreditation guidelines suggest that hospitals conduct a proactive risk assessment when planning construction, and addressing impacts on air quality and infection control, as well as other factors.

Construction may disturb spaces like ceilings and walls that may have received no maintenance or cleaning for decades. Even the most careful contractor will inevitably create dust and fumes. New building materials may release VOCs.

In addition, construction may entail changes to ventilation systems and the building envelope that create pathways for airborne pollutants and water to enter patient spaces.

To reduce such threats, carefully seal construction areas off from protected environments. You may want to use a portable air filter unit to reduce particulates within the construction area. Set up exhaust fans to make the construction area a negative pressure zone and cut pollutant infiltration into patient areas.

Like construction projects, water leaks, floods, and spills are common in a health care setting. If building materials remain wet for more than 72 hours, they may become a base for mold growth.

Combating such problems starts before the moisture arrives. When planning new construction, it is good practice to specify building materials that do not provide a food source for mold.

When leaks and spills do occur, take immediate action. Test for moisture and dry soaked materials within 72 hours. Replace water-damaged materials and those that cannot be dried, or show evidence of mold growth.


When it comes to air quality issues, hospital facility managers face a significant challenge. Hospitals house patients highly vulnerable to airborne infection, as well as those whose coughs and sneezes can spew out dangerous microorganisms. A large and busy staff is constantly on the move within an extremely complex physical infrastructure. Construction and renovation projects and maintenance issues are commonplace.

All of these factors place a high priority on air quality management. The process begins with understanding the air quality requirements of specific hospital functions and patient populations. HVAC systems are designed and operated to deliver the required air quality and pressure in special-purpose facilities, such as protective environment rooms. Finally, system performance is consistently monitored to ensure air conditions meet the institution’s standard of care.

The use of hand-held air quality test instruments makes this maintenance and operation oversight easier. Such tools are accurate, convenient, and easy to use. Most important, they give the technician clear evidence of what is happening in the invisible world of air quality - data that forms the foundation for effective decisions.

Sidebar: Facility Design

Architects and engineers must design health care HVAC systems to control airborne infectious agents and pollutants, manage air pressure and direction of flow, and deliver other air conditions required for the health and comfort of patients and staff. The principles they work with include:

Control air pressure and flow.A key step is to establish pressure relationships that move air from clean environments (higher pressure) to dirty or contaminated areas (lower pressure). You can create pressure differentials by using exhaust fans (as in a restroom or construction area) to reduce pressure, by increasing air supply to boost pressure, and by combining these measures. By stopping leaks in ducts, windows, ceilings, and doors, you can reduce uncontrolled air movement that can disrupt airflow patterns.

Establish appropriate air filtration.Filter air to reduce airborne particle counts to levels appropriate for each facility and function. Minimum filter efficiency should be 90 percent of particles 0.5 microns and larger. In facilities where patients are at greatest risk of airborne infection, such as operating rooms and rooms for bone marrow transplant patients, deliver supply air through high-efficiency particulate air (HEPA) filters.

Add fresh air to the mix.To reduce the levels of gaseous contaminants such as CO2 (a product of human respiration that can be used as an indicator of air exchange levels), add filtered, conditioned outside air to the atmosphere within the facility. Untreated outside air is likely to have more particulates but less CO2 and other gases than inside air.

Monitor system performance.Keep an eye on system function by measuring and logging air quality (relative humidity, temperature, particle levels, and gases) and air pressure and flow regularly, using a combination of fixed and hand-held instruments.

Publication date:11/19/2007