Indoor Air Quality (IAQ) is a current buzzword in the Heating Ventilation and Air Conditioning (HVAC) Industry

We hear about Legionnaire’s disease outbreaks traced to air conditioning systems.  Buildings are highlighted on the news as making their tenants sick and it’s referred to as a “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 level 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. 

Filtering 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 contaminates along with it.  Have your service technician check to verify that all the return air to a system is pulled through a 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 of 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 and home improvement stores.  This type of filter gives the greatest degree of improvement for the money spent.  Replace every one to three 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% - 95% efficiency, these filters are changed 2 to 3 times per year.  Media filters require a special frame to be 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 air flow can greatly reduce the system capacity and efficiency.  A new generation of these filters is now coming to market and they promise less restriction of airflow.  Clean at intervals between 1 to 4 weeks.
• Electronic Air Filters – this is the premier air 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 furniture.

Killing 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 kill 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 per 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.

Also, even older air conditioning units can usually be retrofitted with UV lights.