PERFORMANCE MONITORING

Even in a well-designed facility, performance can decline over time. Blowers fail. Filters 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 can 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.

SIMPLE TECHNIQUES FOR AIR QUALITY MEASUREMENT

Key to the 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; provides an early warning when conditions change, so corrections can be made; and creates 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 do not require 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. Occupants’ activities affect conditions. For instance, they open and close doors, windows, and air vents. Technicians may install filters incorrectly, or fail to replace them on schedule.

Architects and engineers must design healthcare 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.
 

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 display, 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 organic 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 (CO) 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 the temperature is right, provide a base for the growth of mold, which releases spores into the air.

RESPONDING TO ABNORMAL CONDITIONS AND INCIDENTS

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 address impacts on air quality and infection control, as well as other factors.

Construction can 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, and 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 healthcare 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 that show evidence of mold growth.

CONCLUSION

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 healthcare 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 harmful 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.