Air Quality/Ventilation

Indoor Air Quality (IAQ)

At Metro Environmental Services we have many products available to address your Indoor Air Quality issues without compromising your comfort. Call 972-245-1158 today for a comprehensive assessment tailored to your specific needs.

Some Examples of indoor air pollutants:

H1N1 (Swine Flu) Norwalk Virus Mold and Yeast Odors and Smoke Streptococcus

What Causes Indoor Air Problems?

Indoor pollution sources that release gases or particles into the air are the primary cause of indoor air quality problems in homes. Inadequate ventilation can increase indoor pollutant levels by not bringing in enough outdoor air to dilute emissions from indoor sources and by not carrying indoor air pollutants out of the home. High temperature and humidity levels can also increase concentrations of some pollutants.

Indoor Air Pollution and Health

The EPA lists Indoor Air Quality as one of the top five environmental risks to public health today. Health effects from indoor air pollutants may be experienced soon after exposure or, possibly, years later.

Immediate effects

Immediate effects may show up after a single exposure or repeated exposures. These include irritation of the eyes, nose, and throat, headaches, dizziness, and fatigue. Such immediate effects are usually short-term and treatable. Sometimes the treatment is simply eliminating the person’s exposure to the source of the pollution, if it can be identified. Symptoms of some diseases, including asthma, hypersensitivity pneumonitis, and humidifier fever, may also show up soon after exposure to some indoor air pollutants.The likelihood of immediate reactions to indoor air pollutants depends on several factors. Age and preexisting medical conditions are two important influences. In other cases, whether a person reacts to a pollutant depends on individual sensitivity, which varies tremendously from person to person. Some people can become sensitized to biological pollutants after repeated exposures, and it appears that some people can become sensitized to chemical pollutants as well.Certain immediate effects are similar to those from colds or other viral diseases, so it is often difficult to determine if the symptoms are a result of exposure to indoor air pollution. For this reason, it is important to pay attention to the time and place symptoms occur. If the symptoms fade or go away when a person is away from home, for example, an effort should be made to identify indoor air sources that may be possible causes. Some effects may be made worse by an inadequate supply of outdoor air or from the heating, cooling, or humidity conditions prevalent in the home.

Long-term effects

Other health effects may show up either years after exposure has occurred or only after long or repeated periods of exposure. These effects, which include some respiratory diseases, heart disease, and cancer, can be severely debilitating or fatal. It is prudent to try to improve the indoor air quality in your home even if symptoms are not noticeable. While pollutants commonly found in indoor air are responsible for many harmful effects, there is considerable uncertainty about what concentrations or periods of exposure are necessary to produce specific health problems. People also react very differently to exposure to indoor air pollutants. Further research is needed to better understand which health effects occur after exposure to the average pollutant concentrations found in homes and which occurs from the higher concentrations that occur for short periods of time.

Pollutant Sources

There are many sources of indoor air pollution in any home. These include combustion sources such as gas and wood; building materials and furnishings as diverse as deteriorated, insulation, wet or damp carpet, and cabinetry or furniture made of certain pressed wood products; products for household cleaning and maintenance, personal care, or hobbies; central heating and cooling systems and humidification devices; and outdoor sources such as radon, pesticides, and outdoor air pollution. The relative importance of any single source depends on how much of a given pollutant it emits and how hazardous those emissions are. In some cases, factors such as how old the source is and whether it is properly maintained are significant. For example, an improperly adjusted gas stove can emit significantly more carbon monoxide than one that is properly adjusted. Some sources, such as building materials, furnishings, and household products like air fresheners, release pollutants more or less continuously. Other sources, related to activities carried out in the home, release pollutants intermittently. These include smoking, the use of unvented or malfunctioning stoves, furnaces, or space heaters, the use of solvents in cleaning and hobby activities, the use of paint strippers in redecorating activities, and the use of cleaning products and pesticides in house-keeping. High pollutant concentrations can remain in the air for long periods after some of these activities.

Amount of Ventilation

If too little outdoor air enters a home, pollutants can accumulate to levels that can pose health and comfort problems. Unless they are built with special mechanical means of ventilation, homes that are designed and constructed to minimize the amount of outdoor air that can “leak” into and out of the home may have higher pollutant levels than other homes. However, because some weather conditions can drastically reduce the amount of outdoor air that enters a home, pollutants can build up even in homes that are normally considered “leaky”.

How Does Outdoor Air Enter a House?

Outdoor air enters and leaves a house by: infiltration, natural ventilation, and mechanical ventilation. In a process known as infiltration, outdoor air flows into the house through openings, joints, and cracks in walls, floors, and ceilings, and around windows and doors. In natural ventilation, air moves through opened windows and doors. Air movement associated with infiltration and natural ventilation is caused by air temperature differences between indoors and outdoors and by wind. Finally, there are a number of mechanical ventilation devices, from outdoor-vented fans that intermittently remove air from a single room, such as bathrooms and kitchen, to air handling systems that use fans and duct work to continuously remove indoor air and distribute filtered and conditioned outdoor air to strategic points throughout the house. The rate at which outdoor air replaces indoor air is described as the air exchange rate. When there is little infiltration, natural ventilation, or mechanical ventilation, the air exchange rate is low and pollutant levels can increase.

Air Filtration – The first step in protecting your home


Changing your filters regularly is the key to maintaining your system and improving your indoor air quality. There are many types of air filters available. Unfortunately many systems in North Texas were designed for use with high velocity throw-a-way air filters.

If you would like to improve your indoor air quality through better filtration consult Metro Environmental Services today at 972-245-1158 to find the filter or filter system that fits your needs without reducing system capacity and efficiency.

A clean filter promotes your health by improving your home’s air quality. It also allows your air conditioner to run more efficiently, which can save you money on energy bills and help you avoid costly repair or replacement.

Choose the right filter.

There are a number of common filter options available. The right one for you depends on your family’s sensitivity to airborne particles and your system configuration:

  • Disposable fiberglass filters (high velocity) are the least expensive – and also the least effective, designed to block only large dust and dirt particles to protect your furnace. Smaller particles, like pollen and mold, pass right through. Unfortunately many North Texas homes were designed with tight air duct, replacing one of these filters with a better one is not always the best move. Allow Metro Environmental Services to analyze this for you. If allergies and respiratory problems aren’t a concern for your family, a disposable or washable filter can be enough to keep your furnace clean. Service frequency, replace monthly.
  • Washable “electrostatic” filters have a static charge that attracts dust, dirt and other matter. These filters are slightly more effective than disposable, but still block only 15 to 20% of airborne particles. These washable filters are very hard to clean and often become so impacted they must be replaced. In addition, they can restrict the airflow enough that the amp draw on your blower motor increases. When this occurs, you have less efficient air distribution in your home and higher utility costs. Service frequency, wash monthly
  • Pleated “allergy” media filters use a much denser mesh material to trap particles. The pleats increase the surface area, eliminating large allergens like pollen and mold – most are 35 to 50% efficient. 1 inch pleated “allergy” filters are often too restrictive. It is best to select filters with 4 or 5” pleats if your system filter rack will accommodate them. Service frequency, 1” filters must be replaced monthly, 4” filters every three months and 5” filters every 6 months.
  • Electronic air cleaners use electrodes to create an ionized electrical field that “magnetizes” pollutant particles and collects them on the filter material. An electronic unit can eliminate virtually all pollen and mold spores, up to 94% of smaller particles, and even up to 80% of airborne viruses. These filters are very effective but must be installed properly. If not setup to match the system they are installed on they can produce high levels of ozone which is an irritant to many people. Service frequency, pre-filter semiannually and full service annually.
  • A HEPA furnace filter, which stands for High Efficiency Particulate Air filters, is the best residential filtration product available. These filters are used in commercial applications like hospitals, research facilities and electronics manufacturing where clean air is vital. Unfortunately HEPA filters not only block air particles, but also air flow; residentially these filters are installed to treat only a portion of the air at a time. If properly installed, the entire volume of air in the home passes through them every 4 hours.


Odors, Viruses, Mold, Bacteria and VOC’s
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At Metro Environmental Services we recommend and install Air Purification Systems manufactured by Air Knight. Through a process of advanced oxidation Air Knight Products have proven to be extremely effective in reducing, and in many cases eliminating the harmful effects of these indoor pollutants.

Call Metro Environmental Services at 972-245-1158 for a free brochure about this amazing product.

Air Ducts

Proper design and installation are key to system efficiency and indoor air quality. Leaking ducts promote and cause infiltration, reducing the capacity and efficiency of your system. Even more importantly leaking duct systems will cause poor indoor air quality by forcing polluted outdoor or attic air into the home. Lots of people know that spending a little more on a high-efficiency air conditioning or heating system now will pay off big in the long run with lower energy costs, less upkeep and a higher level of comfort.What most people don’t realize is that their equipment is only part of the solution. To completely feel the benefits of your investment, make sure your ductwork is as well thought out and maintained, as your air conditioning equipment.Poorly planned or sloppily installed ducts can negate the energy savings and cost reductions you are counting on and promote poor IAQ through infiltration. Joints that aren’t sealed properly can let a lot of that precious heated or cooled air escape—as can old ductwork that may not be up to par with today’s new standards. Even newer ducts, when placed in areas of extreme temperatures (like attics), can gain too much heat. Good attic ventilation and radiant barriers are solutions to this problem.

Ductwork solutions

One thing you can do is to seal and insulate all ductwork. Minor duct repairs are easy to accomplish, but ducts in unconditioned spaces should be sealed and repaired by a qualified professional using the appropriate sealing materials.

Here are a few duct repair tips:

  • When looking for air leaks, first check sections that should be joined but have separated and then look for obvious holes.
  • If you use duct tape to repair and seal your ducts, look for tape with the Underwriters Laboratories (UL) logo to avoid tape that degrades, cracks, and loses its bond with age.
  • The outer duct “jacket” acts as a vapor barrier; if this barrier is torn atmospheric moisture will enter drawn to the inner duct by the temperature difference. When this occurs the insulation will become wet and lose its insulation ability. All tears should be repaired. If duct is wet or cannot be repaired it should be replaced.

Older homes with original flex duct flex may need an upgrade. The original flex duct used in North Texas had an insulation value of R4, by code R6 duct is the minimum currently in use and R8 duct is in wide use. If your air duct gains 3 or more degrees (from plenum to grill) an upgrade should be considered. For a complete analysis of your air duct delivery system call Metro Environmental today at 972-245-1158