I have an Omtech 60 Watt that I would like to exhaust out my unused chimney. My house used to have an Oil burner for both the hot water and Boiler for heat, but I converted to a Gas high efficiency boiler and hot water heater that exhausts out the front of my house thru a 4-inch PVC pipe, leaving the original Chimney unused. Can I use the chimney to exhaust the Omtech as long as I install a backdraft preventer and I use a 6-inch Blower to send the fumes out the chimney?
If it is blinded to your heating system, it is a nice option. The height of the chimney itself will help transport the smoke from your laser. The smoke is cold in advance and gives only minimal condensation to your chimney.
Yes, the Chimney is not used and would be ideal to get rid of the lasers exhaust.
Do you think that a 400CFM exhaust fan will be enough to push the smoke up and out of the chimney?
I’m going to use solid piping from the laser to the chimney.
That’s through a metal plate covering the fireplace opening, with a blast gate to shut it off when I’m not using the laser. The previous owners had a wood stove vented there and it worked fine for the laser cutter.
I eventually replaced the solid elbows with flex duct, because the downstream elbow joints leaked a surprising amount of fumes under pressure from the blower.
Highly recommended! 
Thanks for the reply…and the recommendation.