Lots of good suggestions.
Yes, breathing unknown vapors is not good. Cancer, allergies, etc. Yet, we really do not know what we are breathing when the lubricant/coolant breaks down from the heat. Organic materials become OTHER organics! We seem to have a tolerance to small amounts of many chemicals, but with repeated use we develop all kinds of reactions to some of them. Because of this I can no longer use Neosporin. I just used it a bit too long trying to keep a wound from getting infected.
I used to work for a chemical company so have worried about this before I started machining. Some of my thoughts about lubricants/coolant processes:
I like to think of lubricant and coolant as two different processes. A lubricant tends to reduce friction and so the heat at the tool tip is decreased. But it probably is of little value if one is cutting rather than rubbing. (rubbing = tool contact without cutting). Cutting will generate heat representing the removal of material. (The atomic level cutting process is not very well understood be we know it is breaking atomic bonds and in our case is also bending the work materials-----which is at least part of the generation of the heat energy.) A rubbing example is a drill bit with two flutes but only one spiral/pig tail cut is coming off. The other flute edge is just rubbing/friction and the heat is making it even more dull. (It is very hard to sharpen a drill bit so that both cutting edges are matched! If you get two pigtails during drilling you have a decent drill bit AND the plunge rate is set up properly to cause both edges to cut! ) A coolant does not have to lower the friction, but may. However, it carries away the heat to keep the tool from over heating. As metal tools heat up such that the cutting edge temperature gets higher, relative to their melting point, the tool metal gets softer and so they dull more quickly. (Carbide tools have very high melting points and so do not dull as rapidly.) So when we generate smoke we know that the lubricant/coolant is either evaporating, breaking down into other organic vapors, or both and boiling to create both other gases or gases with droplets. It may also be carrying the work material with it.
Coolants can function by lowering the work/tool temperature as the coolant gets hotter. The physics of this is the energy needed to raise the temperature of the coolant. For example, the specific heat (heat capacity) of water near freezing is.... one gram (about 1 cubic centimeter) of water increases temperature by 1 degree Celcuis for each Calorie (4.19 Joule) of energy it absorbs. When water boils at 100C, or melts from ice at 0C, its temperature does not increase as it absorbs the energy, but this takes a lot of energy, called the latent energy. To melt ice takes 80 calories per gram (about 1 CC) and to boil water takes 540 Calories/gram.
Clearly water is a great coolant as it comes off as steam! But I don't like to use it as I am fearful of rusting my machine surfaces. But you can get some water based coolants with rust inhibitors mixed in. Hopefully, the water vaporizes before the inhibitors and that the inhibitors are not toxic.
When I first started using a mill, I decided I was going to get the "best" lub/coolant from McMasters-Carr so paid a little extra (MOBILMET 766). Poured a whole gallon in my flood coolant system and started cutting a bunch of steel. The smoke and stink drove me out of the room! I concluded that this had something it that had a low boiling point so as remove heat by utilizing a vapor latent energy process. Then I looked up the Safety Data Sheets and sure enough you are not suppose to breath this stuff. It is probably made for automated, enclosed machine tools! Next try was listed a Food-Grade cutting lubricant, BioCut FG 2000, based upon a Canola oil but has additives. It is not nearly as bad, but still not ideal as the Safety Data Sheet still says to were a respirator. Who knows what it breaks down into. Anyway, not much smoke, but the oil seems to get sticky with use.
New activated Carbon cartridges in your mask will soak up the vapors and the particles cannot get through unless super fine. We all know about N95 mask now. The stop most of the particles, but do little to slow down vapors. If you can smell it is not working or the mask is not tight fitting.
The best solution is lots of ventilation, but if you cannot do this then I would get an electrostatic air cleaner (Smoke Eater?) to try to gather up the molecules and particles. Clean it often. There was a big one in my forced air furnace system when I moved to this house and it does work! Hepa are used filters with lots of fan circulation to take out the really fine particles/droplets and are what are used in both medical operating rooms as well as integrated circuit clean rooms.
I am headed towards more ventilation, but am not their yet. I just put in a new glass block window in my small shop room so that I can use hoses and fans for pushing the air outside through a couple missing blocks hole!
Good luck.
