Managing Indoor Air Quality:
Through Mechanical Operation and Effectiveness
Since most people spend the
majority of their time indoors, the possibility of exposure to
chemical or biological contaminants in problem buildings is
widespread. Indoor air pollution problems typically fall into one of
the following categories: Sick Building Syndrome (SBS), Building
Related Illness (BRI), and Multiple Chemical Sensitivity (MCS). Poor
ventilation, moisture intrusion, improper chemical storage and/or
use are all conditions allowing for indoor air quality problems.
Even though some of these problems have been around since the
beginning of man’s construction of indoor spaces, increased
awareness of indoor air quality issues has been exacerbated lately
because of the confined spaces of many buildings built in the last
few decades. Sustainable building technologies must take these risk
factors into consideration and improve the quality of indoor air in
new and remodeled buildings.
Indoor air quality (IAQ) issues
often center on the mechanical operation and effectiveness of the
heating, ventilation and air conditioning (HVAC) system.
Research has shown that up to 60 percent of IAQ-related problems are
caused by HVAC systems. At the same time, 80 percent of common IAQ
issues are resolved through HVAC modifications. So, HVAC design,
maintenance and operation are all critical elements for maintaining
a quality indoor air environment.
1. Address ventilation systems
during building design or prior to renovation. HVAC system
design and operating parameters should be carefully addressed during
all construction and renovation projects. Public buildings are
frequently used for purposes other than their initial design and
may, in fact, have several different applications during the
building lifetime. Thus, many buildings end up being occupied beyond
the HVAC systems capability and renovations may occur without
readjusting the HVAC system to accommodate the changes.
2. Know your building IAQ
baseline. Most building managers have a through understanding of
how the HVAC system and its limitations work to achieve occupant
comfort. Several comfort parameters should be evaluated periodically
and anytime complaints are derived from occupants. The American
Society of Heating, Refrigeration and Air Conditioning Engineers (ASHRAE)
recommendations for key parameters follow:
Carbon Dioxide (CO2).
CO2 is a product of nature and of human respiration. It is also
an indicator of ventilation effectiveness within a building. CO2
is present in the open environment in average concentrations of
300 to 400 ppm. ASHRAE recommends that indoor CO2 levels be
maintained below 1,000 ppm and other groups recommend below 700
ppm for occupant comfort and productivity. Sleepiness, lethargy
and headaches are early symptoms of higher levels of CO2. A CO2
level approaching this maximum is an indicator of poor air
mixing and represents a general buildup of air contaminants.
Temperature. ASHRAE
recommends that indoor temperatures during the winter months be
maintained between 68 and 75 °F and indoor temperatures during
the summer months should be between 73 and 79 °F. In practice,
complaints may occur with any temperature not maintained at 72
°F with some air circulation.
Relative Humidity.
Relative humidity (RH) is the amount of moisture in the air.
ASHRAE recommends RH be maintained between 30 and 60 percent for
indoor environments. RH below 30 can cause drying of the mucous
membranes and discomfort for many people. RH above 60 for
extended time periods promotes indoor microbial growth.
Air Exchange Rate. HVAC
systems are designed to supply fresh air into the occupied space
supplying fresh air into the building and diluting contaminants
preventing buildup. ASHRAE requires the minimum concentration of
outside air supplied to an occupied building to be 20 cubic feet
per minute (CFM) per person in each occupied zone. If HVAC is
shut down overnight, the system should be started at least one
hour before occupancy to provide adequate ventilation. Other
contributors to stale and poorly mixed air include poor location
of supply and exhaust air diffusers, improper building or system
design (often caused by change of building occupancy from
original design configuration with inadequate attention during
remodeling), or indoor structures that prevent free movement of
air.
Carbon monoxide (CO). CO
is a common result of the presence of or proximity to sources of
combustion. It is present to some degree when fuel-operated
systems are used. High levels are an immediate threat to life.
Lower levels are a cause for health concern. Concentrations
should be maintained as close to nondetectable as possible.
3. Remediate water-damaged
building materials. Water damaged ceiling materials seem to be
the hallmark of modern commercial and public buildings, yet these
materials harbor mold growth potential. When coupled with the higher
humidity of a water intrusion event, the perfect conditions are met
for mold to colonize and reproduce. All porous building materials –
drywall, wood and particleboard – exposed to water should be
replaced quickly to decrease the potential for mold growth. In
addition, products such as wall insulation, carpet and carpet
padding should be removed, discarded and replaced, as they get wet.
Care should always be taken to make
sure that inclement weather does not affect building materials
during new construction or renovation.
Source: Sustainable Lands and
Buildings in North Carolina
Commercial HVAC System and
Air Duct Cleaning Services
