I've been happy with the AirGradient One, which does have VOC measurement, as well as CO2, and PPM 2.5. It seems that VOC on the hardware side is relative, so the amount is just compared to a baseline (last 24 hours in the case of the AirGradient One). Also, VOCs are everywhere, but not necessarily harmful: cooking will spike your VOCs, but that's very different than having a can of varnish open.