Can you run a laser without venting outside?

Yes, on a recirculating fume extractor with real HEPA and generous activated carbon — sized to the machine, with cartridges treated as consumables. It is how apartment and winter-workshop makers operate.

The honest constraints: carbon saturates silently (schedule replacement by hours, not smell), heavy MDF and big acrylic runs will outpace small filters, and "the room smells fine" is a lagging indicator. If a window duct is at all possible, it is cheaper and better.