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Out of sight, out of mind is not a good excuse for avoiding the task.
The heating, ventilation and air-conditioning (HVAC) system is the respiratory system — the lungs — of a building. Return ducts take in air from the occupied space and send it through an air handler, where it is warmed or cooled and returned to the occupied space through a network of supply ducts. A well-maintained system removes the stale gases and provides a steady stream of oxygen-rich, comfortable, odorless air for the occupants. But where there’s air, there’s particulate.
Why be particular about particulate?
According to the Air Quality Management District near Los Angeles, an average cubic inch of local urban air contains about 250,000 particles. This reduces to 25,000 to 50,000 particles near the coast and increases to a million or more near highways. Even a cubic inch of the purest air at mountain peaks and over the center of the ocean holds thousands of particles.
With the rise of nanotechnology, the primary focus in the medical world has been on ultrafine particles known as PM2.5 — particulate matter with a size of 2.5 microns and smaller. These aren’t good for one’s health. High exposure to PM2.5 and larger particles has been linked to an astonishing array of physical ailments, including:
- Strokes (Annals of Neurology, May 2008)
- Blood clots in leg veins (Archives of Internal Medicine, May 2008)
- Wheezing in infants (Thorax, August 2008)
- Alzheimer’s and Parkinson’s (Environmental Factor, May 2008)
- Clogged arteries (Genome Biology, July 2007)
- Heart risks in young adults (American Journal of Respiratory and Critical Care Medicine, August 2007)
- Premature birth (American Journal of Epidemiology online, November 2007)
- Premature death (Thorax online, July 2007)
As air is drawn through an HVAC system, particulates gradually begin to collect on the interior of the ductwork, fan, fan housing, coils and other parts in contact with the air stream. As time goes on, the particles can coat the surfaces to a thickness of three inches or more. Although contaminant buildup usually isn’t more than 0.5 inches deep, sometimes it can be several inches. A two-inch buildup on the bottom of a 12 inch x 12 inch duct makes it a 10 inch x 12 inch duct. This narrowing of the flow area produces more resistance to air going through, adding to the energy bill. A Japanese study in the 1980s, however, found that when the contaminant coating thickness reac hes 0.03 inches, the particulates start to peel off and reenter the air stream.
HVAC systems get dirty over time, but at variable rates. Contaminant accumulation rates and peel-off rates are determined by a variety of factors, including duct size, air speed, air volume, particulate load in the air and particulate size. Some systems accumulate large amounts of debris and some reach a point of near equilibrium, where the rate of accumulation is only slightly higher than the rate of peel-off.
Energy costs
One of the first things to be affected by particulate buildup is energy cost, particularly from the heating and cooling coils. The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) found that simply cleaning the coils after a year of use produced considerable energy savings by increasing the cfm by 14{8dbb22967fc7fa73c00f6d7c46e04cf8b828b38e57a2ec1836779474c12513ec} and by improving heat-transfer ability by 10-25{8dbb22967fc7fa73c00f6d7c46e04cf8b828b38e57a2ec1836779474c12513ec} (ASHRAE Journal, November 2006). But many plants allow their HVAC systems to go years without a good coil cleaning, so it seems reasonable to conclude that industry is missing out on greater energy savings. As time goes on, accumulation on other parts of the system adds to the energy loss.
Some fan blades are slightly cupped to make them aerodynamic. Accumulated dirt alters the fan-blade profile to render them less efficient and they pull fewer cfm. Also, dirt adds weight to the fan, so more energy is required to turn it. A clean fan is cheaper to run. Turning vanes at duct elbows collect particulate matter and all manner of debris over time. I’ve seen cardboard, pieces of insulation and dead birds clogging the elbows.
Clogged registers also introduce inefficiencies. Besides particulate buildup, after five, 10 or 20 years, a lot of foreign objects can find their way into an HVAC system and get caught behind the registers. Because air flow can be restricted in so many ways by particulate buildup, a cleaning can cause a dramatic increase in cfm, particularly in older systems that have never been cleaned.
Preventive measures
You have control over the rate of dirt accumulation in your HVAC system. The following items are the primary contributors to system contamination and efficiency loss:
- Missing filters — not common, but it makes a system dirtier faster
- Filters poorly fitted or with gaps between them
- Improper filters — use those recommended by the OEM
- Dirty filters and failure to clean the filter rack when changing filters
- Neglecting the air handler — not inspecting periodically to spot functional problems
- Dirty operating environment
- Duct leakage — gaps at duct joints, where unfiltered air can be drawn in
- Poor or no condensate drainage in the air handler
- Deteriorated fiberglass liner — friable, small or large pieces get into the ductwork
- Leaks in air handlers — worn door seals or holes in the cabinets
Monitor the symptoms
Unless you’re in a clean environment, such as a hospital, where HVAC cleaning is part of routine maintenance, you might wonder how to make an educated decision on when to clean a system. Here are some basic guidelines.
Replacing or repairing the air handler. When you change a fan, fan motor or the entire air handler, you shake the duct system and loosen the dirt inside it. A new fan likely will blow greater cfm than the old one, giving it enough strength to blast out lots of particulates that would have otherwise remained attached.
A poorly maintained HVAC system. If the filters have been missing or poorly fitted for six months or more, the likelihood is that the fan, coils and ductwork are laden with particulates and debris. A cleaning likely will be needed to give you healthy air output and coils that aren’t clogged.
Mold growth. This is more common in the South, but can be a problem anywhere. Biological growth inside the air handler can emit foul odors and can even make people sick. Mold growth inside the ductwork is less likely, but it can occur. Get mold contamination corrected immediately because failure to remedy it could open your company up to legal consequences.
Dirt blowing out. If system contamination reaches the point where dirt is coming out, covering machinery, desks or an employee’s lunch, you’ve probably hit a point of no return. The only remedy is cleaning the HVAC system thoroughly. Before you make the call, ensure the problem isn’t caused by something simple, like missing filters or an open door on the air handler.
Bad smells. Cigarette smoke, industrial fumes, particulates, algae, fungi, mold — a number of things can settle into a duct system, causing a rank odor when the system is running. We’ve found that the return ductwork is frequently the source of odors. It gets much dirtier than supply ductwork because it pulls in unfiltered air. Cleaning usually remedies this problem.
Dirty ducts or air handler. Sometimes you simply look at the system and common sense tells you it’s filthy and people shouldn’t be breathing air from it.
Air flow is restricted by dirt buildup. When enough particulates and debris collect in critical areas, it can cut air flow dramatically. Coils are a primary culprit because they have narrow air passages. These clog up quickly. Registers, particularly return registers with screen covers, also can become clogged.
Sick occupants. A dirty HVAC system isn’t responsible for every case of sick building syndrome, but it can be a contributor. A study conducted by Allergy Consumer Review (reported at www.allergyconsumerreview.com/air-purifiers-furnace-filters.html) found that HVAC cleaning reduced airborne particulates by about 75{8dbb22967fc7fa73c00f6d7c46e04cf8b828b38e57a2ec1836779474c12513ec} and contributed significantly to a reduction of allergy and illness symptoms in the building.
New construction. It’s nearly impossible to keep construction dust from getting into the HVAC system. The architectural specs for many government buildings mandate a “post-construction blowout” (cleaning) before the system can be used.
There are no set standards regulating how often HVAC cleaning should be performed. For hospitals, which do it more than most facilities, every five to 10 years is common, although coil cleaning might be more frequent. It depends a great deal on how quickly the system gets dirty and the needs of the occupants. The primary factor concerns how often the system exhibits one of the symptoms listed above. Ideally, you want to clean the system before it turns into an emergency; however, coils should be cleaned annually to capture an easy and considerable cost savings.
The cleaning process
Duct cleaning technology has been refined over the years. In the 1980s, the National Air Duct Cleaners Association (NADCA) promulgated industry standards to promote greater professionalism. Today, most reputable duct-cleaning firms are certified NADCA members.
Duct cleaning is usually done during off hours, when operations are shut down, so cleaning contractors work nights and weekends. Duct-cleaning equipment varies by company and even by region, but there are two basic technologies: contact cleaning and negative-air cleaning. With either method, each part of the HVAC system gets cleaned, including the registers, coils, air hander and ductwork.
Contact cleaning is the old-school method. The ductwork is hand-vacuumed. If the ducts are large enough, a technician crawls the interior. If not, the ducts are cleaned by cutting access holes every 15 feet or so, reaching in and vacuuming. Contact cleaning is the most thorough method but, because it can be more labor intensive (and thus more costly), it’s not used very often. However, even on some modern jobs, part of the work might require contact cleaning.
Negative-air-cleaning technology has been developed during the last 20 years. It involves a large vacuum (known as a negative-air machine) attached to a duct opening to produce a powerful draw of air through a section of ductwork. A variety of tools can be run through the duct while the vacuum is operating. Hoses can blast air and augers (long cables with a spinning brush on the end) can agitate the particulate into the air stream for the negative-air machine to collect.
Regardless of approach, industry best practices say that it’s insufficient simply to connect a strong vacuum up to the duct. Some kind of contact agitation, such as air blasting or mechanical brushing, is required on the interior duct surfaces to remove particulates more effectively. NADCA standards also dictate that either method must use vacuum devices equipped with high efficiency particulate air (HEPA) filters that catch particles as small as 0.3 microns.
Design problems
Manufacturing processes can release oil mist, lint, sawdust and all manner of particulate matter into the air. Any HVAC system is at risk for contamination in such an environment, particularly if the return or intake registers draw air from the particulate-filled zone. Such contamination not only increases energy costs, but can be a fire hazard if the material is flammable.
Some industrial and commercial venues can exhibit serious HVAC contamination. This is particularly true if a system shares air with industrial processes that release airborne particulate matter. A classic example was a California hotel, where the HVAC system’s large fresh-air intake opening was just above a gigantic laundry exhaust vent. The HVAC system had to cool air that was 20°F hotter than normal outside air. Lint also clogged the filters and coils and caused rapid ductwork buildup.
The HVAC air intake register at a cooking facility was too close to the cooking area. Smoke from the cooking process — which includes minute droplets of grease and steam — was drawn into the HVAC system. Food odors came through the ductwork and grease accumulated on the coils, filters and ductwork. Cleaning this system was an arduous exercise.
The best advice for such situations is to design the system properly in the first place so it doesn’t cross-contaminate from the industrial process — primarily by not drawing from particulate-laden air. If you already have an HVAC system with a poor design, an HVAC engineer might be able to redesign the filtration or reroute the ductwork to solve the problem.
A quality HVAC system can be a luxury when it runs well with little attention. But, just like dependable old friends, they occasionally let us know they need a helping hand. When they become overloaded with particulate and debris, problems begin. HVAC cleaning is a well-established procedure for remedying a contaminated system. When done properly by a reputable company, it can improve air quality, restore system functionality and reduce the cost of running it.
Dan Stradford is CEO of Action Duct Cleaning Co. Inc.
April 2009 Clean HVAC System Coils Save Energy Dirty coils force compressors to run longer and work harder than required, increasing energy usage and utility costs Dirty coils force compressors to run longer and work harder than required, increasing energy usage and utility costs COURTESY OF NADCA One of the easiest, most cost-effective green things you can do for your building’s energy efficiency is to have your HVAC system’s condenser and evaporator coils inspected yearly and cleaned as necessary. Dirty coils force compressors to run longer and work harder than required, increasing energy usage and utility costs while decreasing component life and occupant comfort. According to the U.S. Environmental Protection Agency (EPA), the U.S. Department of Energy (DOE), major utilities, and other experts, dirty condenser and evaporator coils can significantly increase HVAC energy usage and associated utility costs. The U.S. DOE says that “a dirty condenser coil can increase compressor energy consumption by 30 percent.” A dirty evaporator coil decreases airflow, resulting in reduced heat transfer and a degradation of the dehumidification process. These can cause overall air quality to decline and systems to fail, and decrease the life expectancy of motors due to increased heat while running. NADCA Standards The ACR 2006 Standard for HVAC Assessment, Cleaning and Restoration includes details regarding methodologies for coil cleaning and occupant protection strategies. It also helps building owners and managers quantify HVAC-system performance before and after cleaning, calling for HVAC systems to operate within 10 percent of their nominal and/or design volumetric flow after coil cleaning (other factors aside). Using NADCA-certified air-system cleaning specialists ensures that the systems are properly cleaned and maintained for increased energy efficiency and reduced energy consumption. Pacific Gas & Electric (PG&E) suggests an annual coil cleaning to its commercial customers as part of its ongoing efforts to promote energy-efficient HVAC-system operations. “Once the system has been properly charged with refrigerant and has good airflow across the indoor coil, and assuming there is no damage to the duct system, only basic service, such as changing filters and cleaning the outdoor unit annually, should be needed to maintain the system operation at peak performance levels,” says PG&E. With the HVAC system running in “cool” mode, there are two places where heat exchange occurs: 1) condensing unit coils, and 2) evaporator coils. Foreign materials on these coils act as unintended insulators and inhibit the free flow of air through the coils, decreasing the rate of heat transfer between coil and air that is the basis of most HVAC systems. Further, experience shows that servicing dirty systems can lead to misdiagnosing problems and/or faulty or unnecessary repairs. Typically, this results in overcharging of systems and premature failure. It’s not just old systems that need cleaning. In fact, the newer and more efficient your HVAC system is, the more likely it is to benefit from regular coil inspection and cleaning. These newer systems operate at greatly increased pressures and are less tolerant of increases in static pressure. While clean coils have always been important, today’s higher-efficiency units require more efficient heat transfer across larger coils to function at their highest capacity. New units with high SEER ratings often have variable-speed fan motors that adjust fan speed based on demand; however, these units lose much of their effectiveness when forced to run harder than necessary due to fouled condenser vanes. An effective coil inspection and cleaning requires more than hosing down the vanes on an exterior compressor coil. The National Air Duct Cleaners Association’s (NADCA) ACR 2006 Standard for HVAC Assessment, Cleaning and Restoration sets minimum best practices for coil cleaning. Building Use Air-Handling Unit Supply Ductwork Return Ductwork/Exhaust Industrial 1 year 1 year 1 year Residential 1 year 2 years 2 years Light Commercial 1 year 2 years 2 years Commercial 1 year 2 years 2 years Healthcare 1 year 1 year 1 year Marine 1 year 2 years 2 years Robert “Buck” Sheppard is president of the Washington, D.C.-based National Air Duct Cleaners Association.
DO YOU SUSPECT YOUR OFFICE HAS AN INDOOR AIR PROBLEM?
Indoor air quality problems are not limited to homes. In fact, many office buildings have significant air pollution sources. Some of these buildings may be inadequately ventilated. For example, mechanical ventilation systems may not be designed or operated to provide adequate amounts of outdoor air. Finally, people generally have less control over the indoor environment in their offices than they do in their homes. As a result, there has been an increase in the incidence of reported health problems.
Health Effects
A number of well-identified illnesses, such as Legionnaires’ disease, asthma, hypersensitivity pneumonitis, and humidifier fever, have been directly traced to specific building problems. These are called building-related illnesses. Most of these diseases can be treated, nevertheless, some pose serious risks.
Sometimes, however, building occupants experience symptoms that do not fit the pattern of any particular illness and are difficult to trace to any specific source. This phenomenon has been labeled sick building syndrome. People may complain of one or more of the following symptoms: dry or burning mucous membranes in the nose, eyes, and throat; sneezing; stuffy or runny nose; fatigue or lethargy; headache; dizziness; nausea; irritability and forgetfulness. Poor lighting, noise, vibration, thermal discomfort, and psychological stress may also cause, or contribute to, these symptoms.
There is no single manner in which these health problems appear. In some cases, problems begin as workers enter their offices and diminish as workers leave; other times, symptoms continue until the illness is treated. Sometimes there are outbreaks of illness among many workers in a single building; in other cases, health symptoms show up only in individual workers.
In the opinion of some World Health Organization experts, up to 30 percent of new or remodeled commercial buildings may have unusually high rates of health and comfort complaints from occupants that may potentially be related to indoor air quality.
What Causes Problems?
Three major reasons for poor indoor air quality in office buildings are the presence of indoor air pollution sources; poorly designed, maintained, or operated ventilation systems; and uses of the building that were unanticipated or poorly planned for when the building was designed or renovated.
Sources of Office Air Pollution
As with homes, the most important factor influencing indoor air quality is the presence of pollutant sources. Commonly found office pollutants and their sources include environmental tobacco smoke; asbestos from insulating and fire-retardant building supplies; formaldehyde from pressed wood products; other organics from building materials, carpet, and other office furnishings, cleaning materials and activities, restroom air fresheners, paints, adhesives, copying machines, and photography and print shops; biological contaminants from dirty ventilation systems or water-damaged walls, ceilings, and carpets; and pesticides from pest management practices.
Ventilation Systems
Mechanical ventilation systems in large buildings are designed and operated not only to heat and cool the air, but also to draw in and circulate outdoor air. If they are poorly designed, operated, or maintained, however, ventilation systems can contribute to indoor air problems in several ways.
For example, problems arise when, in an effort to save energy, ventilation systems are not used to bring in adequate amounts of outdoor air. Inadequate ventilation also occurs if the air supply and return vents within each room are blocked or placed in such a way that outdoor air does not actually reach the breathing zone of building occupants. Improperly located outdoor air intake vents can also bring in air contaminated with automobile and truck exhaust, boiler emissions, fumes from dumpsters, or air vented from restrooms. Finally, ventilation systems can be a source of in door pollution themselves by spreading biological contaminants that have multiplied in cooling towers, humidifiers, dehumidifiers, air conditioners, or the inside surfaces of ventilation duct work.
Use of the Building
Indoor air pollutants can be circulated from portions of the building used for specialized purposes, such as restaurants, print shops, and dry-cleaning stores, into offices in the same building. Carbon monoxide and other components of automobile exhaust can be drawn from underground parking garages through stairwells and elevator shafts into office spaces.
In addition, buildings originally designed for one purpose may end up being converted to use as office space. If not properly modified during building renovations, the room partitions and ventilation system can contribute to indoor air quality problems by restricting air recirculation or by providing an inadequate supply of outdoor air.
What to Do if You Suspect a Problem
If you or others at your office are experiencing health or comfort problems that you suspect may be caused by indoor air pollution, you can do the following:
- Talk with other workers, your supervisor, and union representatives to see if the problems are being experienced by others and urge that a record of reported health complaints be kept by management, if one has not already been established.
- Talk with your own physician and report your problems to the company physician, nurse, or health and safety officer.
- Call your state or local health department or air pollution control agency to talk over the symptoms and possible causes.
- Encourage building management to obtain a copy of Building Air Quality: A Guide for Building Owners and Facility Managers from the EPA. Building Air Quality (BAQ) is simply written, yet provides comprehensive information for identifying, correcting, and preventing indoor air quality problems. BAQ also provides supporting information such as when and how to select outside technical assistance, how to communicate with others regarding indoor air issues, and where to find additional sources of information. To obtain the looseleaf-fomat version of the Building Air Quality, complete with appendices, an index, and a full set of useful forms, and the newly released, Building Air Quality Action Plan, order GPO Stock # 055-000-00602-4, for $28, contact the: Superintendent of Documents, U.S. Government Printing Office (GPO), P.O. Box 371954, Pittsburgh, PA 15250-7954, or call (202) 512-1800, fax (202) 512-2250.
- Obtain a copy of “An Office Building Occupant’s Guide to Indoor Air Quality,” EPA-402-K-97-003, October 1997 from IAQ INFO at 1-800-438-4318.
- Frequently, indoor air quality problems in large commercial buildings cannot be effectively identified or remedied without a comprehensive building investigation. These investigations may start with written questionnaires and telephone consultations in which building investigators assess the history of occupant symptoms and building operation procedures. In some cases, these inquiries may quickly uncover the problem and on-site visits are unnecessary.
- More often, however, investigators will need to come to the building to conduct personal interviews with occupants, to look for possible sources of the problems, and to inspect the design and operation of the ventilation system and other building features. Because taking measurements of pollutants at the very low levels often found in office buildings is expensive and may not yield information readily useful in identifying problem sources, investigators may not take many measurements. The process of solving indoor air quality problems that result in health and comfort complaints can be a slow one, involving several trial solutions before successful remedial actions are identified.
- If a professional company is hired to conduct a building investigation, select a company on the basis of its experience in identifying and solving indoor air quality problems in nonindustrial buildings.
- Work with others to establish a smoking policy that eliminates involuntary nonsmoker exposure to environmental tobacco smoke.
- Call the National Institute for Occupational Safety and Health (NIOSH) for information on obtaining a health hazard evaluation of your office (800-35NIOSH), or contact the Occupational Safety and Health Administration, (202) 219-8151.