I'm living in an addition to an existing home done four years ago, drywalled with possible toxic materials. How do you clean this up?
The addition is 606 sq. ft. above a garage. Very lovely, but I have had various problems since living here. It was not done with green builders.
Hard question to answer without first asking a few questions. What makes you think there are toxic materials in your home? Sickness? Allergies? Odor? There are not many building materials out there that are really bad for you -- there are some concerns about home air quality with certain materials when there is a very tight structure. If your builder did not use "green practices," then I doubt your home is so tight that you are in danger of any toxic offgassing. The only other issue could be a mold problem inside your wall, but in Arizona I would not think you have much of a moisture problem.
I would be more concerned with the fact that you live over a garage. The fumes from a car are more dangerous than any building material. If sickness or flu-like symptoms are your problem, it could be low levels of carbon monoxide -- often misdiagnosed.
For starters, install a fan in the garage that will automatically come on and run for 15 minutes every time a car enters or leaves the garage. This can be installed for a very low cost, and Panasonic makes fans with a motion sensor and a timer that shouldn't be very hard to install. This will allow the carbon monoxide to escape so it won't seep up into your living area.
If you are still concerned with possible toxic materials, you can have a building analyst come out and run a blower door test to see how tight your house is. There are calculations that can be done to find the Building Airflow Standard, which is the minimum amount of ventilation required -- if you are below this level, additional ventilation can be installed to get rid of your "bad/stale air" and replace it with fresh air from the outside. This same test can determine how connected your living area is to your garage and help come up with a solution for your carbon monoxide problem.
I would highly recommend a high-dollar digital carbon monoxide detector. The cheap ones at the box stores are only programmed to come on at 400 parts per million, but you will want one that can measure low levels -- 0-35 ppm. If the detector even a low level of carbon monoxide, you need to tighten up the air sealing between the garage and your living area and increase the ventilation in each area as well.