for you guys in these really cold climates, it’s probably best to do a good filter system combined with a low CFM heat exchanged fresh-air system. Def not as easy as us in the southern areas.
You might want to expand on this a bit. To me, it means (low CFM heat exchanged) means a low amount of air let into the house and heated before it comes in.
The 400 CFM with suction I suggested because if you build the filter box big enough, you can increase the speed as needed until the air flow stops. Plus I don’t know the length of the run to outdoors.
You need fresh air, from outside, let into the house or laser to exchange the air. Depending on your heating system, you can create a fresh air duct that gets heated before entering the laser enclosure. As noted here.
It depends on your enclosure, design etc. Most small embers will be out by the time they are only a foot away or less. You should never run it unattended. Always have a fire extinguisher nearby.
This also goes for not extracting enough smoke. It will coat the mirrors and even just affect the beam. You have a diode laser so it won’t affect any mirrors, but it can coat the laser lens and interfere with the beam.
It might even be better to draw it straight in at cold temps since it is a diode. You’ll get more power, longer life etc.
what I meant was build a filter box and have your laser sucking from and dumping into the room all of its air but the exhaust is filtered. To take care of any leaking getting some fresh air into the room would be helpful but you don’t want cold air so the way to do that is to blow a little bit of room air outside but use that air to heat the small amount of fresh air entering from the cold outside using a heat exchanger.
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If he builds a good enough filter box, he can intake and exhaust directly into the room.
1st filter, electrostatic to catch bigger particles and embers.
2nd filter, pleated washable pre filter.
3rd filter MERV 5-8
4th (and or 5th) MERV 16 to catch any all particles that can be ingested, or skip filter 3 and 4 and just use a replaceable HEPA.
Final Filter activated Carbon to finish off any smoke odors.
You’d have to test it though, and always be mindful of leaks. Or, you know, spend $500 -$1200 for an industrial HEPA
It is the most correct solution but also requires that the external intake and exhaust have the required distance, otherwise you suck the bad air directly in again.
But the problem with me is not so big, I accept some negative pressure and heat loss. The temperature never gets below 16 degrees Celsius in my laser machine.
Nb. my water temperature I have set to run between 17 and 20 degrees C, it works flawlessly.
If your filter system works as well as it looks in the pictures then you are good running. You need to save the plans, I’ll probably come sometime and ask for them. 
I am in process of building a new filtration system and new high static pressure fan to pull air through. I also have a fresh air intake that will replace the right hand side door. It will pull air over the surface and into a very large filtration system that will be easy to clean and change. It’ll be nearly as I described.
Electrostatic filter, Prefilter, MERV 8, MERV 15 and finally, Activated Carbon. Still exhausting directly outside. I want to make sure the smell is minimal for my neighbors. I’ll post pics once setup.
Air movers come in many types. Really only the impeller type is viable.
inline axial flow fans usually can’t pull against static pressure. The blades stall and it just doesn’t flow.
Another factor- this flow is dirty. It encrusts grills and vanes. It’s a weirdly low density, mostly dry crud. Knocks off easily, washes off too. But left alone, it clogs things.
Squirrel cage blowers- like in HVAC- do pull some static, but have a tendency to quickly pick up encrustation and stops flowing. A filter in front of it would need to catch a lot and would have to be changed quite regularly.
OK, here’s some ideas:
If you don’t want all that CFM of replacement air freezing your room, what if you have an exhaust out of the cutter and a fresh air intake that brings in outside air ONLY into the laser cutting area? You’d need to consider if the temps/humidity are a problem, but this does make sense.
Another thought- if you want a filter that would allow you to exhaust into the room, why not run the filter outlet back into the laser cutter? Any traces of particulate smoke or trace of VOC would at get a chance of being caught by the filter on successive passes. You would need a split where some air is recirculated and some isn’t, just to maintain negative pressure in the frame and prevent smoke from leaking out .
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That’s a woodshop filter, for dust alone. Prob is, lasers are all fine particle smoke and VOCs. VOCs need activated carbon to filter out, but the smoke needs to be well-filtered before then to prevent the dust from coating the activated carbon and deactivating it
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Yes, that’s why the MERV 15 or 16 before the carbon filter. You can get finer, but you need more static pressure to pull it through. I also recommend venting it outside. I am going to filter to carbon to vent outside as I live in an apartment complex and while it will dissipate, it won’t dissipate enough.
I am working on a project of Industrial extraction system design, after reading this thread I got a lot of info about my assignment. I see different designs with their specifications etc. Overall my experience was amazing. Thanks for posting.