One of the firsts test to check is Radon. Radon is a colorless, odorless, radioactive gas. Tests for radon are very inexpensive compared to other indoor air quality tests.
Carbon Monoxide monitors. Each home should have a carbon monoxide monitor, they are also inexpensive and will not only test your air, they can save your life, as carbon monoxide can be deadly.
Dosimeters. These can test for volatile organic compounds, specific chemicals and/or materials.
You can purchase monitors or detectors to measure; formaldehyde, nitrogen dioxide, water vapor and other pollutants. The devices can be setup inside your home for a specified period of time, and then sent back to a lab for proper analysis.
