The common problem of poor IAQ can be broken down into the following two categories:

1. Backdrafting
   Air pressure indoors is often lower than that outdoors. If the level of depressurization exceeds the strength of the chimney draft, the combustion exhaust air in the flue will flow backwards into the home. This can cause the release of the deadly gas carbon monoxide into a home, causing numerous health concerns.
   
   
2. Odors and Allergies
   EPA studies have found that pollutant levels inside can be two to five times higher than outdoors. After some activities, indoor air pollution levels can be 100 times higher than outdoors. There are many sources of pollutants in the home. Obvious ones are chemicals, cleaning products, and pesticides. Less obvious are pollutants caused by such simple tasks as cooking, bathing, or heating the home. Let's take a closer look at the problems pollutants can cause:
   
   
   • Allergies: During wet weather, openings in the envelope allow water to leak into the home. Water leaks can cause a number of problems including, rot and collapse of plaster or wallboard, molds (which contribute to poor indoor air quality) and can create/exacerbate health problems like allergies. The polluted air can make individuals with allergies feel worse and mold can be toxic.
   • Dust: Over two thirds of dust in houses originates outdoors, and is tracked in on feet. House dust is known to contain many hazardous materials and can be an asthma trigger.
   • Odors/Fresh Air: Sealing against air leakage can reduce heat loss and energy bills, but it can also affect indoor air quality by reducing natural ventilation or by restricting the amount of air available for certain appliances. Restricting the amount of air available can cause certain appliances to spill dangerous by-products into the house.
   
   Energy efficient homes can reduce health risks from mold, dust mites, and other contaminants. They offer fewer entry points for dust and pollen, insects, rodents and other pests. Energy efficient homes also experience less condensation, which protects framing, windows, and finish materials. Better control of moisture and temperature means less movement of materials. Careful attention must be paid throughout the construction and design process to the common problems and the methods to solve these problems. By using implementing energy efficient measures and systems, grantees can help families and their communities.

What are some possible solutions? See Poor Indoor Air Quality.