To have acommercially skilled air quality testing professional come in will run you significantly more than a DIY test and is most likely overkill, but you should be able to learn a lot about what's causing the health hazards in your home and how best to improve your indoor air quality from the professional you hire.
A great local service in SoCal to check out is Dan Thomsen's"The Building Doctors."He's a really valuable and trusted resource to us SoCal residents.
Do-it-yourself kits can cost as little as $90 to test for just a few things, but to get formaldehyde and VOC testing the cost rises to above $300.
There was an excellent do-it-yourself kit exhibitor fromAirLabat Santa Monica's Alt Build Expo last weekend. Best one I've seen yet. It's a little pricey at $499, but the test quality and how the results are displayed are excellent!
All kits that I've seen so far have a small collection tube or device of some sort that you'll set up in your home for about 24 to 48 hours and then send off to the manufacturer's lab for testing.
If you need to use the results for any sort of litigation, you'll need to have a professional set up the test for you.
You candefinitely use a DIYindoor air quality testing kit with great success.
I would doAirlab's $499 test, if that's in your budget. With that info, you'll be able to make a lot of changes in the products you buy or discover anything major that's causing air pollution in your home.
From there you can hire someone like The Building Doctors to physically test and improve your HVAC system or your home's building envelope.
For more information:
Read Evan Little's answer to the question "What are the top five ways to improve my indoor air quality naturally?"
Also check our home air quality Q&A to see what other questions are being asked and answered.