Indoor Air Quality (IAQ) is a current
buzzword in the Heating, Ventilation and Air Conditioning
We hear about Legionnaire's disease outbreaks traced to the
air conditioning system. Buildings are highlighted on the
news as making their tenants sick and it's referred to as
sick building syndrome. Individual homes are linked to increases
in allergies and asthma. Can it happen to your home and what
can you do to prevent it or correct it if you are already
the proud owner of a house that is making you sick?
The ever-increasing cases of sick building syndrome are
due to the way houses and buildings are constructed to conserve
energy. Stop air movement in and out of the home and you reduce
the energy required to heat and cool the house. After you
seal the house up, central cooling and heating systems maintain
livable temperatures and humidity levels within the home by
re-circulation of the same air and pollutants day after day.
Dust, bacteria, viruses, mold, fungus, mildew and gases circulate
through the building. The dust can come from skin, hair, clothes
or just come off shoes when we walk in and out. The mildew,
fungus and molds can come in along with the dust or we can
grow our own in the HVAC system. The gases are volatile organic
compounds that are given off by dyes, paints, varnishes and
adhesives used in modern building materials. The best example
of gases is that burning eye sensation we get after new carpet
is installed. So let's look at Filtering
The Dust, Killing the Mildew, Molds,
and Viruses and Ventilating
the Volatile Gases in an attempt to breathe easier.
the Air We Breathe
The most important step in filter improvement is to make
sure that all the air that goes through the electric air handler
or gas furnace is filtered. If your HVAC system is pulling
air through cracks in the duct system or return air chase,
it pulls the contaminates along with it. Have your service
technician check to verify that all the return air to a system
is pulled through the filter system. This is a good time for
your service technician to verify that the filter system is
sized large enough for proper operation of the system.
Filters come in different efficiencies that are measured
in the percentage of arrestance of particles. Simply stated,
what amount and size of particles do they stop? The
higher the percentage, the smaller the particle the filter
will stop. The other factor that must be considered is the
resistance to air flow, or will this super filter let enough
air through to allow my system to function properly?
Fiberglass - these are the most inexpensive filters
that you can buy. Most people refer to them as the filter
you can see through. They stop 15 % of the largest particles
in the air. Replace monthly.
Pleated Paper - these filters look like a paper version
of drapery pleats and stop up to 45% of the particles in the
air. This type filter is the easiest upgrade for the money
spent. These filters come in the same size as a fiberglass
filter and are available at most hardware/home improvement
stores. This type of filter gives the greatest degree of improvement
for the money spent. Replace every 1 to 3 months.
Media Filter - these filters are up to 4 inches thick
and come in limited sizes, though the size selection is increasing.
Rated at 90 to 95 % efficiency, these filters are changed
2 to 3 times a year. Media filters require a special frame
to be mounted in the wall or mounted directly to the furnace
or air handler. There are some media filters that come with
special adapters that allow them to be mounted in a standard
filter frame that has 4 inches of clearance behind it.
Electrostatic filters - As an upgrade to Fiberglass
filters, these are made up of layers of synthetic material
that generate an electrical charge to attract dust particles.
Electrostatic filters come with guarantees from five years
to life. There have been problems due to high restriction
of airflow across the filter. This reduction of airflow can
greatly reduce the system capacity and efficiency. A new generation
of these filters is now coming to market that promises less
restriction to airflow. Clean at intervals of between 1 to
Electronic Air Filters - this is the premiere filter
system on the market today. An electrostatic grid is powered
when the AC or heat comes on and attracts particles to it.
The grid is cleaned as needed with a water hose or in the
dishwasher. This is the most efficient filter system available.
This type of filter normally fits the same space as a Fiberglass
filter, but does require modification to the ductwork and
wiring to be installed in your air conditioning system.
Some contractors pre-filter either the media or the electronic
filter with a pleated paper filter and move their cleaning
or replacement to a yearly schedule. The main idea regardless
of the type of filter you choose is to filter all the air
you circulate in your house and to remove as much dust and
other particles as needed to breathe comfortably. One benefit
of the high efficiency filters is a reduction in the need
to dust the furniture.
the Mildew, Molds, Fungus, Bacteria, and Viruses
One of the ways our air conditioning system keeps us comfortable
is by removing the water vapor (humidity) from the air. As
the AC system condenses moisture from the air, a drain is
supposed to take this moisture out of the system. What really
happens is that some of this water splashes on the interior
insulation and some of it is left standing in the bottom of
the pan that is not designed or installed to get it completely
out of the system. So, now, we have moisture ready to support
the growth of assorted micro-organisms that will cause a variety
of respiratory problems.
The simplest treatment is to keep drain lines clear and
to have a positive drainage on the coil.
Pan tablets and drain pads are available that release chemicals
into the condensed water and kills the pathogens. These tablets
or pads must be physically placed in the evaporator drain
pan on a 1 to 6 month schedule.
UV lights are the newest tool to be used to improve indoor
air quality. Similar to the lights that barbers, dentists,
and doctors use to sterilize their instruments, these lights
are designed to not only kill what's growing in the drain
pan, but also what is growing on the coil surface or on the
interior insulation. These lights will kill the source of
numerous allergens that people did not know existed. The light
shines on the inside of the AC, in front of the coil, 24 hours
a day. Even if a new bulb is required every year, the UV light
combined with a good filter system will greatly improve the
quality of air in either a home or business.
Even older air conditioning units can usually be retrofitted
with UV lights.
As home construction has produced tighter homes, reaction
to gases released from building materials has increased. The
trick is to bring in fresh air without having to heat, cool
or dehumidify it. This can be accomplished in several ways
and must be routed through the filter system.
Heat Exchangers - exhaust air is pushed through a
tubular heat exchanger as fresh air is pulled in around the
outside of the tubes, allowing the air to exchange heat. The
exchanger does not bring hot air down to room temperature
or cold air up to room temperature but does reduce the temperature
difference and the energy needed to bring it to the desired
temperature. This solution guarantees fresh air will enter
the house and stale air will be exhausted along with the toxic
Desiccant Wheels - similar to heat exchangers but
use a rotating wheel to remove humidity from the incoming
air and add it to the exhausted air. Desiccant wheels will
be used were humidity is the greater problem; heat exchangers
will be used where low winter temperatures are the greatest
In conclusion, these various methods to improve air quality
can be built into a new or replacement system at the time
of installation to achieve the best-cost savings. Any of these
improvements can also be added to an existing system. You
may find relief with just improving your filter system or
with a filter and an ultraviolet light. However you mix and
match to achieve breathable air, your licensed HVAC contractor
can provide you with the needed expertise and quality equipment
to accomplish the job.
Please direct any questions to firstname.lastname@example.org.
We look forward to hearing from you!