We cannot recommend specific indoor air quality (IAQ) consultants or testing companies. You can find some guidance for selecting companies providing IAQ services at web sites listed below.
You should first determine how thick of a filter your forced air heating or heating and air conditioning system can accommodate. Many residential systems have space for only a one inch thick filter. The see-through flat panel filters often used in these locations are not recommended because they remove very few of the small particles that pose health risks.
You should consider emissions of VOCs not only the carpet, but also the underlying carpet pad or adhesive. A document from the U.S. Environmental Protection Agency provides guidance and links to the Carpet and Rug Institute’s Green Label program for carpets, carpet cushions, and adhesives.
The first priority is to prevent or fix leaks of liquid water into the building or building envelope. Water entry through the above-grade roof and walls and water entry through surfaces in contact with the soil should be prevented. For above-grade leaks, normal maintenance measures, such as replacing or repairing the roof will often be all that is needed; however, professional assistance may be needed if there were errors in design or construction of the home.
In the selection of a portable air cleaner, sometimes called an air purifier, you should consider 1) the air cleaner’s clean air delivery rate (CADR) for particles; 2) whether the air cleaner removes gaseous pollutants as well as particles; 3) the level of noise produced by the air cleaner; 4) electricity cost, initial cost, filter replacement cost; 5) whether the air cleaner produces ozone or other undesirable pollutants.