Hi there. Do read some of the posts here on Welding Fumes.
Now, I am a safety fanatic so take this stuff with a grain of salt..don't let it scare you, but make you think:

Here are a few tips:

Ventilation pulling out and away from you is good. Pulling away in front - not pulling back towards (and through) your breathing space. Also, when evacuating air, you need an air source. So, behind you, have some air sources. An open window okay or two is fine.

Then, for sure, get a carbon monoxide detector. Nighthawk is the brand preferred by many friends around here. A safety conscious knife maker friend had no idea how much CO2 was in his shop. Now, keep in mind all the other air intakes in your house (such as intake for furnace). Make sure that the fumes you create don't go there.

Along the floor, make sure that the wall or wall edging goes all the way down to the floor. Usually when drywall is put up, there is a space left between floor and that wall. It is for the convenience when installing if there is the possibility of moisture. Anyway, make SURE that the place where the wall and floor are tight. One shop where I worked had a very minor spill of molten metal bee-bee's...and some went under that floor space...into an adjacent wood working shop! Just happenstance that someone noticed.

When I did leather work in the basement, I made a hood which evacuated outside through a window. A fan pulling out there..and windows open behind. Hood came down to my nose level. The item of concern was orthodichlorobenzene. Benzene is bad stuff.

The bedrooms are above. Make sure that you have a reasonable thickness of drywall. Some counties/States require a certain thickness of drywall if the garage is below bedrooms. Gee, I would double it. And what about the possible heat area above the furnace? I would be tempted to put up a layer of sheet metal.

And of course, fire extinguishers in several places. Decent size ones. You have two exits? I would make sure family members know how to use a fire extinguisher. Practice. Why not? One other thing which was discussed on this list in 1996: if a fire extinguisher is used on a person, send the fire extinguisher with the ambulance and person. There are many types and docs cannot treat well without knowing what type used.

Also, I would stay away from Brass. Bronze better since there is no (or less) zinc in it. Also, stay away from a leaded brass. Lead makes fumes but also puts an unseen dust on everything which is just as toxic over time.

Post this and ask BP Fink on Casting Group. He is really knowledgeable on this.

Valerie Weihman-Rock
Artist, Farmer, Educator
Argyle, WI USA