Question: Are there any other professional instruments that measures different VOC besides PID (photoionisation detector)?

Answers came in from @nshapiro

"You could try a summa canister: http://summacanister.com/ (they are offered by many labs not just this one). it is basically a sterile bowling ball that has all of the air vacuumed out of it and then you put it in your house and open the valve and it sucks in air at a known rate and then you take that to the lab and they can run a full analysis on all the chemicals they find in there. my guess is that it would be under 500 including shipping and analysis.

The other option is some people will rent you instruments so you could rent a fancy HCHO meter for a day and get all your measurements that way. without the huge investment.

BUT saying all this, you might want to just try remediation as often in manufactured housing its hard to get rid of the engineered woods that off-gas hcho.... I would avoid spending [the money on a PID VOC meter]. I'm also not sure if they can measure as low as you would want as you will be looking at parts per billion not parts per million. They are often made for use in heavy industry where they have crazy high levels."

Wow i wasn't familiar with PID sensors. I skimmed the Wikiepedia page here:

https://en.wikipedia.org/wiki/Photoionization_detector

And also found this pretty readable post about limitations or possible issues with them: https://www.levitt-safety.com/blog/the-problem-with-pids/

Do we know how much they cost? I'm guessing a lot? Google Shopping suggests maybe $500-5000: https://www.google.com/search?tbm=shop&q=pid+sensor+gas

As to detection, Wikipedia says down to parts per billion? from sub parts per billion to 10 000 parts per million (ppm)

The one in the article above was $3000-4000 -- https://www.google.com/search?tbm=shop&q=tiger+voc#spd=857929050906658907

It says it is sensitive down to 1 part per billion: A robust VOC detector Tiger provides a dynamic detection range of 0 to 20,000 parts per million (ppm) with a minimum sensitivity of 0.001ppm (1 ppb), offering the widest measurement range of any other VOC detector on the market.

But they seem to have a pretty tough calibration procedure involving some kind of calibration machine.

I did see some available for rent, so maybe they'd come precalibrated?

I'm becoming familiar with the MeteoMex suite of sensors from @robert_winkler that includes tVOC monitoring and could serve as a low-cost place to start investigating. There's not so much about these sensors on Public Lab yet, but you can read more about them here: http://www.meteomex.com and see an example output here.