I have my X1C sitting in my home office. Also, I have a Air Quality monitor in there. Normally the AQI (Air Quality Index*) sits around 1 or 2, even when printing.
However, I just printed some parts with wood-infused PLA. The AQI jumped to an ungodly 230. Ho-lee-■■■■. Opened the window, ran an air-circulating fan, plus the air-filtering fan I have, then got out of the office while that was going on. Let that be a warning to you all; that nice-smelling wood smell, while subtle, is quite unhealthy.
* For the non-US folk, AQI is in the range of 0, meaning really good, to 500. 301+ is considered “Hazardous”.
I do not know what kind of equipment you have to measure, but most cheap consumer stuff just measures particle density for PM10 or PM2.5 and CO. Heating wood to 220+ °C will emit those fumes, and more so as the wood particles are nothing more then sawdust size.
Those levels aren’t good, but they usually are not a big concern unless you are spending half your lifetime in such an environment. Light a few candles and you will also see AQI go through the roof.
But clearly it doesn’t hurt to keep a window open and not sit right next to the printer for many hours, but its still far away from a toxic level.
It measures PM1.0, 2.5 and 10, with a separate readout for each, plus an overall AQI according to some forumula that isn’t simply “highest” or “average” as far as I can tell. LMK if you want me to hunt down the purchasing link.