HVAC System
Cleanliness Impacts
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HVAC System Cleanliness
Impacts Operating Costs and IAQ
Maintaining acceptable indoor air
quality and controlling operating costs are issues on the mind of every plant
manager and administrator in the country. With potential liability and
possible lost productivity on the line. The need for an IAQ risk management
plan for commercial facilities is paramount. However, due to varied building
designs and ages, on-going renovations, and ever changing demands and
building uses, implementing such a plan is rarely clear-cut. Often, measures
that improve indoor air quality, such as increasing ventilation, Drive up
building energy consumption. Upgrades to more efficient filters (which create
higher static pressure drops) can also result in increased facility’s
operating costs. How can indoor air quality be improved without sacrificing
energy efficiency? The key to a successful lAQ strategy is regular maintenance of heating, ventilating,
and air conditioning (HVAC) systems. These systems also account for a sizable
portion of a facility's operating costs. Regular inspections for cleanliness
and performance of air handling systems (AHS) fans, coils, airflow control
devices, and ductwork are not the "norm." Often, filter change and
other minimal procedures are the only maintenance activities performed
regularly. Anything beyond that is
usually repair work when specific problems arise. The unfortunate reality is,
however, that these are the systems relied upon to remove the building's foul
air and replace it with clean, conditioned air for a safe. Comfortable indoor
environment. Acceptable IAQ is
often difficult to quantify, as is the effect of system contamination on IAQ.
From a practical stand point, though. it would be
hard to imagine a dirty, contaminated HVAC air handler and duct system having
a positive impact on IAQ! One thing is quite clear: Dirty systems cost more
to operate. Unlike the evasive standards for IAQ, empirical measurements for
airflow, pressure drops, and thermal transfer may be accurately observed.
From these it is possible to document HV AC performance both before and after
cleaning. Such information can be used to show how cleaning air-handling
systems can reduce operating costs and pay for the work in energy savings. Studies initiated
by several utility companies around the country have noted considerable
operating cost reductions after cleaning critical HVAC system components such
as coils and fans. Plant renovations may serve to complicate matters by
altering airflow patters changing area usages, and introducing many
contaminants, Renovations can create elevated airborne particulate levels as
well as off-gassing from construction materials. Potential IAQ problems can
often be avoided by careful planning prior to construction work at a
facility. The HVAC systems
serving the areas under construction may transport these construction-related
contaminants to other areas of the building. It is therefore critical to
completely zone-off (or decommission) any air-handling systems that tie
renovation areas with other parts of the building. After work is completed,
these HVAC systems need to be inspected and cleaned of construction debris
prior to re-commissioning and occupancy. Without a
deliberate program in plaice to monitor the performance and maintenance of
the HVAC air-handling systems, providing acceptable indoor air quality may be
difficult (if not impossible). The once heralded IAQ "cure-all" of
simply increasing ventilation rates to occupied areas has several
shortcomings. First. a facility’s HVAC systems are
of [en already operating at or near peak output. Common measures to increase
airflow in these instances can result in greatly increased energy consumption
and operating cost - not a desirable tradeoff.
Efforts to increase
ventilation rates also be hampered by dirty coils,
turning vanes, fire dampers, and other HVAC components clogged with debris.
Second, and of possibly greater concern to decision makers, increasing
supply-side airflow through a dirty HV AC duct system can worsen IAQ
problems, Increasing air flow
through an ill-maintained HVAC system will indeed lower CO2 levels and help
dilute VOCs and other gaseous toxins, However,
increased air flow will also readily distribute more particulates from the
contaminated HVAC ducts to occupied areas. Consider that few air-handling
systems are designed with access points for proper inspection and maintenance
throughout. As a result, supply, return, and exhaust segments of a building's
air-handling system may be filled with dust, mold. and
other potential allergens and pathogens. A sound approach to managing IAQ
risks must include regular, thorough inspection and cleaning, if necessary, of a facility's air-handling systems.
Verifying that the HV AC systems are clean is also important prior to air
balancing. as delivery rates can be greatly affected
by contaminant buildup (especially in reheat coils and bathroom and shower
exhaust systems). Facility managers
and administrators need both parameters to judge the HVAC cleanliness level
as well as methods of inspecting and evaluating their systems. One such guide
is the first in a series of standards for air-handling system cleaning
adopted by the National Air Duct Cleaners Association (NADCA). This initial
document (available from NADCA's headquarters in Acceptable levels of
cleanliness are based on a NADCA developed surface particulate vacuum test.
This test is an important first step in the industry to define a
"clean" air-handling system. The objective is to give both the
service contractor and the facility manager a uniform method by which to
evaluate the need for AHS clean- ing services, as
well as a way to judge the level of services provided. Future NADCA standards
are slated to cover porous AHS components (fiberglass duct board and acoustic
duct liner), as well as project containment and IAQ
standards for these type of remediation projects. Equally important
as standards are methods to actually inspect and evaluate HVAC systems in the
field. Cutting-edge technology for several IAQ industry leaders includes
remote video-assisted inspection and cleaning equipment, along with standard
optical devices such as bore-scopes and video mini-cameras, which now can
provide a look at what once may have been "inaccessible" areas in
HV AC duct systems. The combination of standards, photographic documentation,
and eye-guided cleaning devices offers facility managers superior remediation
work and easy verification of conditions inside HV AC systems. Of course, HV AC air-handling system
cleaning alone may, at times, be a symptomatic treatment, rather than an
actual cure to an existing IAQ problem. For successful remediation, it is
essential to address the source of the IAQ problem that is causing the
contamination in the AHS. Otherwise, even the most thorough HV AC cleaning
procedures will only provide short-term benefits to a building's indoor air
quality. System
maintenance
is a basic, essential component of a building's overall indoor air quality program - often the
"front-line" defense for a
facility's occupants. Areas of special concern
for engineers and managers should include: upgrading Filtration is needed,
regular scheduled maintenance of HV AC equipment, and evaluation of
activities within the building that contribute to poor IAQ. Visible mois- ture and animal debris in
the AHS are also clear warning signs that indicate the need for action. Once it has been
established that there is an actual need, it is critical to ensure that
occupant exposure to any chemicals and contaminants at all phases of an HV AC
cleaning project are minimized. Material Safety Data Sheets must be reviewed
for any proposed chemical products, and the risks benefits evaluated prior to
their use. Containment procedures, especially when service contractors must
work above the ceiling in occupied areas, must be followed. Any vacuums or
negative air devices that Are exhausted within the
building envelope should utilize HEPA (99.97% to 0.3 micron) efficiency
filtration to limit possible occupant exposure. Debris removed from HVAC
system should be disposed of properly, in accordance with any applicable
regulations, Proper HVAC system
maintenance in conjunction with corrective measure to the problem's source provide a
more comprehensive approach to improving u building's IAQ. The added benefit,
and often a clear financial justification, is restoring HV AC systems to
near-original performance and reducing operating costs, HVAC air-handling
system cleaning has never, and will never, be the solution to indoor air
pollution, System maintenance
is a basic, essential component of a building's overall indoor air quality
program often the "front-line" defense for a facility's occupants,
With the ever-increasing emphasis on improving our indoor environments; these
services will undoubtedly continue to play II vital role in IAQ. and will increase public under- standing of when and how
HVAC system inspection/cleaning services should be performed. Bob Krell is president of IAQ Technologies, lnc., The views and
opinion of contributors to Duct Tales are their own, and do not necessarily
represent those of NADCA officers, directors, members or staff. Editorial
comments to articles presented in Duct Tales are always welcome. |
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© United Safety
Services, Inc. 2001 |