Laser Supply Air System.

[Rich Harman]

Rich,

I may be misinterpreting Dan's thoughts (apologies if I am Dan), but I think he was objecting to outside air being brought directly into the laser from outside.

I object to that as well. His reply included my quote where I said "...does not include venting directly into the laser."

Recycling the air through a filter system is not practical for everyone. I do mostly cutting on my laser, lots of smoke and sticky residue. To filter all that out would cost a fortune in filters. The next best thing would be to warm up the incoming replacement air by steeling some heat from the exhaust. What most people do is just exhaust outside and draw unheated replacement air from the outdoors - and they do so without experiencing any trouble.

[Bill George]

Coming from a commercial/industrial career in the HVAC/R field there are OSHA and EPA requirements for cutting and processing certain materials and its been too many years to recall what they are. Exhausting to the outside and bringing in outside air is pretty basic, if the make up air has been heated or cooled is the not the regulating authority's problem. Dan's concern was that dumping ice cold outside air directly into the laser would cause problems.

The make up does not need to be connected directly to the machine, just available. If a simple air to air or pipe inside the pipe works to some degree its better than nothing. But they do make heat wheels and other much more efficient methods to recover the heat or cooling from the exhausted air. It may not be cost effective to spend $10,000 to recover heat when Dan's method is available. If it meets OSHA or EPA requirements for all materials or not would remain to be seen.

[Dan Hintz]

I may be misinterpreting Dan's thoughts (apologies if I am Dan), but I think he was objecting to outside air being brought directly into the laser from outside. A second 4 or 6 inch hose coming off your machine connected straight to outdoors. As your blower moves smokey air from the laser to the outside, air is replaced directly from outside through the second hose, through which you get cold, moist air brought straight into the laser. I think that was his concern. If your laser is replacing blown air from the ambient air in your shop the outside air that is seeping in to replace your blown out air has a chance to warm up some and the moisture coming in with it dissipates through the room so the impact inside the laser is much less.

His preference was not to blow the machine's air outside at all, but instead to run it through filters and feed it right back to the shop so it was not impacting your heating bill, and not sucking colder, moister air directly into the laser.

This ^^^^^

I object to that as well. His reply included my quote where I said "...does not include venting directly into the laser."

Recycling the air through a filter system is not practical for everyone. I do mostly cutting on my laser, lots of smoke and sticky residue. To filter all that out would cost a fortune in filters. The next best thing would be to warm up the incoming replacement air by steeling some heat from the exhaust. What most people do is just exhaust outside and draw unheated replacement air from the outdoors - and they do so without experiencing any trouble.

I do a number of wooden plaques, and while it's not plywood and all of the nasty glue involved, the smoke from pine can be pretty "resiny" (my new word for the day). I do not spend a lot of money on filters. Instead, the first filter my exhaust hits is the cheap throwaway furnace filters you get 10 to a pack at your local fix-it store. With resinous woods, those filters can get clogged quickly, but at practically pennies a piece, I'm okay with swapping them out every few days during a busy period. I lose zero heat to the outside world by exhausting it back into the shop, and my Dylos air meter shows no discernible increase in particulate matter during processing.

[Rich Harman]

I think it is the smoke which requires expensive HEPA filters. The furnace filters that I have tried don't do much to remove smoke.

I think a big problem with filtering and exhausting back into the room with a DIY setup is that you need to be able to monitor it's effectiveness. Not just particulate but also harmful gasses, some of which are odorless. If it filters out 99% that means that you are continuously adding 1% as you use it. If you don't run it much then that is probably safe enough but I would not trust it to remove everything when running for hours at a time cutting the type of stuff that I do. I don't think you can be sure of it's effectiveness without expensive monitoring equipment.

Exhausting outside is safest. Nearly everyone does it, and does so without causing other troubles. Using a double wall pipe to recover some of the heat is not going to introduce any additional troubles. The only issue is you need to be sure that no exhaust mixes with the incoming replacement air. Something well within any good DIYer's abilities.

[Dan Hintz]

I think it is the smoke which requires expensive HEPA filters. The furnace filters that I have tried don't do much to remove smoke.

Correct... but it's not like I run the furnace filters on their own, I use them in front of my filtering system. The cheap furnace filters get rid of the resiny stuff so my main system doesn't get overwhelmed. The main system contains activated carbon and HEPA filtration, so I have everything covered. When I do really nasty stuff (which isn't often), I make sure the carbon is fresh... otherwise, I keep a watch on it and replace as necessary.