How To Monitor Indoor Air Quality?

Foobot Indoor Air Quality Monitor
Foobot Monitors Indoor Air Pollution 24/7 for just $199
It comes with an iPad app as well. 

Biological air pollutants are found to some degree in every home, school, workplace and hospital. Sources include outdoor air and human occupants who shed viruses and bacteria, animal occupants (insects and other arthropods, mammals) that shed allergens, and indoor surfaces and water reservoirs where fungi and bacteria can grow, such as humidifiers. A number of factors allow biological agents to grow and be released into the air. Especially important is high relative humidity, which encourages house dust mite populations to increase and allows fungal growth on damp surfaces. Appliances such as humidifiers, dehumidifiers, air conditioners, and drip pans under cooling coils (as in refrigerators) and especially HVAC system coils support the growth of bacteria and fungi.

Health Problems Caused By Volatile Organic Compounds:

Formaldehyde, Pesticides, Solvents, Cleaning Agents.

Key signs/symptoms:

Conjunctival irritation, nose, throat discomfort, headache, allergic skin reaction, dyspnea, declines in serum, cholinesterase levels, nausea, emesis, epistaxis (formaldehyde), fatigue, dizziness