> Lasers normally require some ventilation via a small tube out a nearby window. Our optional Air Filter that sits under Glowforge and ventilates using HEPA filters and charcoal, meaning no outside ventilation is required.
Best to my knowledge HEPA and charcoal don't help against CO. So running one with the filter in an unventilated space might still be hazardous.
Carbon monoxide is a few orders of magnitude too small to be caught by a HEPA filter, in fact a filter that could filter CO would filter oxygen and nitrogen as well. Such a filter would just be a pump.
There, however, exists a patent for a filter for CO, it works by converting the CO to CO2: https://www.google.com/patents/US5564065
This technique is routinely used to generate concentrated supplies of oxygen or nitrogen, but is wildly expensive compared to ventilation.
(It's not quite as simple as just putting one in-line with the waste gas flow- the catalyst would also need to be externally heated.)